This type is intended to be used to classify internet protocols.In
computing, a protocol is a convention or standard that controls or
enables the connection, communication, and data transfer between two
computing endpoints. In its simplest form, a protocol can be defined as
the rules governing the syntax, semantics, and synchronization of
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The Internet protocol suite is the set of communications protocols used for the Internet and similar networks, and generally the most popular protocol stack for wide area networks. It is commonly known as TCP/IP, because of its most important protocols: Transmission Control Protocol (TCP) and Internet Protocol (IP), which were the first networking protocols defined in this standard. It is occasionally known as the DoD model due to the foundational influence of the ARPANET in the 1970s (operated by DARPA, an agency of the United States Department of Defense).
TCP/IP provides end-to-end connectivity specifying how data should be formatted, addressed, transmitted, routed and received at the destination. It has four abstraction layers, each with its own protocols. From lowest to highest, the layers are:
The TCP/IP model and related protocols are maintained by the (IETF) or Internet Engineering Task Force.
The Internet protocol suite resulted from research and development conducted by the Defense Advanced Research Projects Agency (DARPA) in the early 1970s. After initiating the pioneering ARPANET in 1969, DARPA started work on a number of other data transmission technologies. In 1972,
Secure Hypertext Transfer Protocol (S-HTTP) is a little-used alternative to the HTTPS URI scheme for encrypting web communications carried over HTTP. S-HTTP is defined in RFC 2660. It was developed by Eric Rescorla and Allan M. Schiffman.
Web browsers typically use HTTP to communicate with web servers, sending and receiving information without encrypting it. For sensitive transactions, such as Internet e-commerce or online access to financial accounts, the browser and server must encrypt this information. HTTPS and S-HTTP were both defined in the mid-1990s to address this need. Netscape and Microsoft supported HTTPS rather than S-HTTP, leading to HTTPS becoming the de facto standard mechanism for securing web communications.
S-HTTP encrypts only the served page data and submitted data like POST fields, leaving the initiation of the protocol unchanged. Because of this, S-HTTP could be used concurrently with HTTP (unsecured) on the same port, as the unencrypted header would determine whether the rest of the transmission is encrypted.
In contrast, HTTPS wraps the entire communication within SSL, so the encryption starts before any protocol data is sent. This creates a "chicken and
The Common Industrial Protocol (CIP) is an industrial protocol for industrial automation applications. It is supported by ODVA.
Previously known as Control and Information Protocol, CIP encompasses a comprehensive suite of messages and services for the collection of manufacturing automation applications – control, safety, synchronization, motion, configuration and information. It allows users to integrate these manufacturing applications with enterprise-level Ethernet networks and the Internet. It is supported by hundreds of vendors around the world, and is truly media-independent. CIP provides a unified communication architecture throughout the manufacturing enterprise. The Common Industrial Protocol (CIP) is used in EtherNet/IP, DeviceNet, CompoNet and ControlNet.
ODVA is the organization that supports network technologies built on the Common Industrial Protocol (CIP). These also currently include major application extensions to CIP: CIP Safety, CIP Motion and CIP Sync.
Integrated Services Digital Network (ISDN) is a set of communications standards for simultaneous digital transmission of voice, video, data, and other network services over the traditional circuits of the public switched telephone network. It was first defined in 1988 in the CCITT red book. Prior to ISDN, the telephone system was viewed as a way to transport voice, with some special services available for data. The key feature of ISDN is that it integrates speech and data on the same lines, adding features that were not available in the classic telephone system. There are several kinds of access interfaces to ISDN defined as Basic Rate Interface (BRI), Primary Rate Interface (PRI) and Broadband ISDN (B-ISDN).
ISDN is a circuit-switched telephone network system, which also provides access to packet switched networks, designed to allow digital transmission of voice and data over ordinary telephone copper wires, resulting in potentially better voice quality than an analog phone can provide. It offers circuit-switched connections (for either voice or data), and packet-switched connections (for data), in increments of 64 kilobit/s. A major market application for ISDN in some countries
The JSON format was originally specified by Douglas Crockford, and is described in RFC 4627. The official Internet media type for JSON is application/json. The JSON filename extension is .json.
The JSON format is often used for serializing and transmitting structured data over a network connection. It is used primarily to transmit data between a server and web application, serving as an alternative to XML.
Douglas Crockford was the first to specify and popularize the JSON format.
JSON was used at State Software, a company co-founded by Crockford, starting around 2001. The JSON.org website was launched in 2002. In December 2005, Yahoo! began offering some of its web services in JSON. Google started offering JSON feeds for its GData web protocol in December 2006.
Although JSON was based on
The Real-time Transport Protocol (RTP) defines a standardized packet format for delivering audio and video over IP networks. RTP is used extensively in communication and entertainment systems that involve streaming media, such as telephony, video teleconference applications, television services and web-based push-to-talk features.
RTP is used in conjunction with the RTP Control Protocol (RTCP). While RTP carries the media streams (e.g., audio and video), RTCP is used to monitor transmission statistics and quality of service (QoS) and aids synchronization of multiple streams. RTP is originated and received on even port numbers and the associated RTCP communication uses the next higher odd port number.
RTP is one of the technical foundations of Voice over IP and in this context is often used in conjunction with a signaling protocol which assists in setting up connections across the network.
RTP was developed by the Audio-Video Transport Working Group of the Internet Engineering Task Force (IETF) and first published in 1996 as RFC 1889, superseded by RFC 3550 in 2003.
RTP is designed for end-to-end, real-time, transfer of stream data. The protocol provides facility for jitter
The Internet Control Message Protocol (ICMP) is one of the core protocols of the Internet Protocol Suite. It is chiefly used by the operating systems of networked computers to send error messages indicating, for example, that a requested service is not available or that a host or router could not be reached. ICMP can also be used to relay query messages. It is assigned protocol number 1.
ICMP differs from transport protocols such as TCP and UDP in that it is not typically used to exchange data between systems, nor is it regularly employed by end-user network applications (with the exception of some diagnostic tools like ping and traceroute).
ICMP for Internet Protocol version 4 (IPv4) is also known as ICMPv4. IPv6 has a similar protocol, ICMPv6.
The Internet Control Message Protocol is part of the Internet Protocol Suite, as defined in RFC 792. ICMP messages are typically used for diagnostic or control purposes or generated in response to errors in IP operations (as specified in RFC 1122). ICMP errors are directed to the source IP address of the originating packet.
For example, every device (such as an intermediate router) forwarding an IP datagram first decrements the time to live
UDT (acronym for UDP Data Transport) is a protocol developed by the National Center for Data Mining (NCDM) at University of Illinois at Chicago. The protocol was designed to sit on top of User Datagram Protocol (UDP) to facilitate large data transfers over modern high-speed fiber optic computer networks. In October, 2003 the NCDM achieved a 6.8 gigabits per second transfer from Chicago, USA to Amsterdam, Netherlands. During the 30-minute test they transmitted approximately 1.4 terabytes of data.
StarLAN was the first implementation of 1 megabit per second (1Mbit/s) Ethernet over twisted pair wiring. It was standardized by the standards association of the Institute of Electrical and Electronics Engineers (IEEE) as 802.3e in 1986, as the 1BASE5 version of Ethernet.
StarLAN was developed by AT&T Corporation around 1984. The name comes from using a star topology for a local area network. The standard known as 1BASE5 was adopted as 802.3e in 1986 by members of the IEEE 802.3 standards committee as the Twisted Pair Medium Specification in section 12. StarLAN ran at a speed of 1 Mbit/s.
A major design goal in StarLAN was the reuse of existing telephony on-premises wiring and compatibility with analog telephone signals in the same cable bundle. The signal modulation and wire pairing used by StarLAN were carefully chosen so that they would not affect or be affected by either the analog signal of a normal call, on hook and off hook transients, or the 20 Hz high-voltage analog ring signal. Reuse of existing wires was critical in many buildings where rewiring was cost prohibitive, or where running new wire would disturb asbestos within the building infrastructure.
The TIA-568B wiring
The ISDN User Part or ISUP is part of the Signaling System #7 which is used to set up telephone calls in Public Switched Telephone Networks. It is specified by the ITU-T as part of the Q.76x series.
When a telephone call is set up from one subscriber to another, many telephone exchanges will be involved, possibly across international boundaries. To allow a call to be set up correctly, where ISUP is supported, a switch will signal call-related information like called or calling party number to the next switch in the network using ISUP messages.
The telephone exchanges are connected via E1 or T1 trunks which transport the speech from the calls. These trunks are divided into 64 kbit/s timeslots, and one timeslot can carry exactly one call. Each timeslot between two switches is uniquely identified by a Circuit Identification Code (CIC) that is included in the ISUP messages. The exchange uses this information along with the received signalling information (especially the Called Party Number) to determine which inbound CICs and outbound CICs should be connected together to provide an end to end speech path.
In addition to call related information, ISUP is also used to exchange status
Digital Command Control (DCC) is a standard for a system to operate model railways digitally. When equipped with Digital Command Control, locomotives on the same electrical section of track can be independently controlled.
The DCC protocol is defined by the Digital Command Control Working group of the National Model Railroad Association (NMRA). The NMRA has trademarked the term DCC, so while the term Digital Command Control is sometimes used to describe any digital model railway control system, strictly speaking it refers to NMRA DCC.
A DCC command station, in combination with its booster, modulates the voltage on the track to encode digital messages while providing electric power.
The voltage to the track is a bipolar DC signal. This results in a form of alternating current, but the DCC signal does not follow a sine wave. Instead, the command station quickly switches the direction of the DC voltage, resulting in a modulated pulse wave. The length of time the voltage is applied in each direction provides the method for encoding data. To represent a binary one, the time is short (nominally 58µs for a half cycle), while a zero is represented by a longer period (nominally at least
In computer networking, Layer 2 Tunneling Protocol (L2TP) is a tunneling protocol used to support virtual private networks (VPNs) or as part of the delivery of services by ISPs. It does not provide any encryption or confidentiality by itself; it relies on an encryption protocol that it passes within the tunnel to provide privacy.
Published in 1999 as proposed standard RFC 2661, L2TP has its origins primarily in two older tunneling protocols for Point-to-Point communication: Cisco's Layer 2 Forwarding Protocol (L2F) and USRobotics Point-to-Point Tunneling Protocol (PPTP). A new version of this protocol, L2TPv3, was published as proposed standard RFC 3931 in 2005. L2TPv3 provides additional security features, improved encapsulation, and the ability to carry data links other than simply PPP over an IP network (e.g., Frame Relay, Ethernet, ATM, etc.).
The entire L2TP packet, including payload and L2TP header, is sent within a User Datagram Protocol (UDP) datagram. It is common to carry Point-to-Point Protocol (PPP) sessions within an L2TP tunnel. L2TP does not provide confidentiality or strong authentication by itself. IPsec is often used to secure L2TP packets by providing
Transaction Capabilities Application Part, from ITU-T recommendations Q.771-Q.775 or ANSI T1.114 is a protocol for Signalling System 7 networks. Its primary purpose is to facilitate multiple concurrent dialogs between the same sub-systems on the same machines, using Transaction IDs to differentiate these, similar to the way TCP ports facilitate multiplexing connections between the same IP addresses on the Internet.
TCAP is used to transport INAP in Intelligent Networks and MAP in mobile phone networks.
TCAP messages are sent over the wire between machines. TCAP primitives are sent between the application and the local TCAP stack, all TCAP messages are primitives but there are primitives that are not messages, i.e. some are only transferred inside the local machine. A TCAP primitive is made up of one or more TCAP components.
An ITU-T TCAP primitive may be one of the following types:
A Begin primitive has an Originating Transaction ID (up to 4 bytes). Continues have an Originating Transaction ID and a Destination Transaction ID. Ends and Aborts only have a Destination Transaction ID. Each primitive has both an optional component and (required) dialogue portions. The component portion
Systems Network Architecture (SNA) is IBM's proprietary networking architecture created in 1974. It is a complete protocol stack for interconnecting computers and their resources. SNA describes the protocol and is, in itself, not a single piece of software. The implementation of SNA takes the form of various communications packages, most notably Virtual telecommunications access method (VTAM) which is the mainframe package for SNA communications.
SNA was made public as part of IBM's "Advanced Function for Communications" announcement in September, 1974, which included the implementation of the SNA/SDLC (Synchronous Data Link Control) protocols on new communications products:
They were supported by IBM 3704/3705 communication controllers and their Network Control Program, and by System/370 and their VTAM and other software such as CICS and IMS. This announcement was followed by another announcement in July, 1975, which introduced the IBM 3760 data entry station, the IBM 3790 communication system, and the new models of the IBM 3270 display system.
SNA was mainly designed by the IBM Systems Development Division laboratory in Research Triangle Park, North Carolina, USA, helped by other
ICQ is an instant messaging computer program that was first developed and popularized by the Israeli company Mirabilis, then bought by America Online, and since April 2010 owned by Mail.ru Group.
The first version of the program was released in November 1996 and ICQ became the first Internet-wide instant messaging service, later patenting the technology. AOL acquired Mirabilis on June 8, 1998, for US$287 million in cash up front and $120 million in additional payments over three years.
In 2001, ICQ had over 100 million accounts registered. In April 2010, AOL sold ICQ to Digital Sky Technologies for $187.5 million.
Mirabilis was first established in June 1996 by five Israelis: Yair Goldfinger, Sefi Vigiser, Amnon Amir, Arik Vardi, and Arik's father Yossi Vardi. They recognized that many people were online accessing the Internet through a non-UNIX operating system, and that there was no software that enabled an immediate connection between them.
What was missing was the technology for locating and connecting the users of the Windows operating system.
The technology Mirabilis developed for ICQ was distributed free of charge. The technology's success caused AOL to acquire Mirabilis on
Napster is a name given to two music-focused online services. It was originally founded as a pioneering peer-to-peer file sharing Internet service that emphasized sharing audio files, typically music, encoded in MP3 format. The original company ran into legal difficulties over copyright infringement, ceased operations and was eventually acquired by Roxio. In its second incarnation Napster became an online music store until it merged with Rhapsody on 1 December 2011.
Later companies and projects successfully followed its P2P filesharing example such as Gnutella, Freenet and many others. Some services, like Grokster, Madster and the original eDonkey network, were brought down or changed due to similar circumstances.
Napster was co-founded by Shawn Fanning, John Fanning, and Sean Parker. Initially, Napster was envisioned as an independent peer-to-peer file sharing service. The service, named after Fanning's hairstyle-based nickname, operated between June 1999 and July 2001. Its technology allowed people to easily share their MP3 files with other participants. Its ease of use led to massive copyright violations of music and film media, as well as other intellectual property. Although
Web Distributed Authoring and Versioning (WebDAV) is an extension of the Hypertext Transfer Protocol (HTTP) that facilitates collaboration between users in editing and managing documents and files stored on World Wide Web servers. A working group of the Internet Engineering Task Force (IETF) defines WebDAV in RFC 4918.
The WebDAV protocol makes the Web a readable and writable medium. It provides a framework for users to create, change and move documents on a server; typically a web server or web share. The most important features of the WebDAV protocol include the maintenance of properties about an author or modification date, namespace management, collections, and overwrite protection. Maintenance of properties includes such things as the creation, removal, and querying of file information. Namespace management deals with the ability to copy and move web pages within a server’s namespace. Collections deals with the creation, removal, and listing of various resources. Lastly, overwrite protection handles aspects related to locking of files.
The WebDAV working group concluded its work in March 2007, after the Internet Engineering Steering Group (IESG) accepted an incremental update
STUN is a standardized set of methods, including a network protocol, used in NAT traversal for applications of real-time voice, video, messaging, and other interactive IP communications. STUN is an acronym for Session Traversal Utilities for NAT, and is documented in RFC 5389. RFC 5389 obsoletes the previous specification, entitled Simple Traversal of User Datagram Protocol (UDP) through Network Address Translators (NATs), documented in RFC 3489. The obsolete version of STUN, sometimes referred to as Classic STUN, was intended as a complete solution for NAT traversal, and featured an algorithm to allow endpoints to determine NAT behaviour. The current version of STUN is presented as a tool to be used by other protocols, such as ICE. STUN removes the NAT classification algorithm and defines an extensible packet format.
The STUN protocol allows applications operating behind a network address translator (NAT) to discover the presence of the network address translator and to obtain the mapped (public) IP address (NAT address) and port number that the NAT has allocated for the application's User Datagram Protocol (UDP) connections to remote hosts. The protocol requires assistance from a
The Lightweight Directory Access Protocol (LDAP; /ˈɛldæp/) is an application protocol for accessing and maintaining distributed directory information services over an Internet Protocol (IP) network. LDAP is defined in terms of ASN.1 and transmitted using BER.
Directory services may provide any organized set of records, often with a hierarchical structure, such as a corporate email directory. Similarly, a telephone directory is a list of subscribers with an address and a phone number.
LDAP is specified in a series of Internet Engineering Task Force (IETF) Standard Track Request for Comments (RFCs). The latest version is Version 3, published as RFC 4511.
Telecommunication companies' understanding of directory requirements was well developed after some 70 years of producing and managing telephone directories. These companies introduced the concept of directory services to information technology and computer networking, their input culminating in the comprehensive X.500 specification, a suite of protocols produced by the International Telecommunication Union (ITU) in the 1980s.
X.500 directory services were traditionally accessed via the X.500 Directory Access Protocol (DAP), which
Simple Authentication and Security Layer (SASL) is a framework for authentication and data security in Internet protocols. It decouples authentication mechanisms from application protocols, in theory allowing any authentication mechanism supported by SASL to be used in any application protocol that uses SASL. Authentication mechanisms can also support proxy authorization, a facility allowing one user to assume the identity of another. They can also provide a data security layer offering data integrity and data confidentiality services. DIGEST-MD5 provides an example of mechanisms which can provide a data-security layer. Application protocols that support SASL typically also support Transport Layer Security (TLS) to complement the services offered by SASL.
In 1997 John Gardiner Myers wrote the original SASL specification (RFC 2222) while at Carnegie Mellon University. In 2006 that document was made obsolete by RFC 4422, edited by Alexey Melnikov and Kurt Zeilenga.
SASL is an IETF Standard Track protocol and is, as of 2010, a Proposed Standard.
A SASL mechanism implements a series of challenges and responses. Defined SASL mechanisms include:
The GS2 family of mechanisms supports
VLAN Trunking Protocol (VTP) is a Cisco proprietary protocol that propagates the definition of Virtual Local Area Networks (VLAN) on the whole local area network. To do this, VTP carries VLAN information to all the switches in a VTP domain. VTP advertisements can be sent over ISL, 802.1q, IEEE 802.10 and LANE trunks. VTP is available on most of the Cisco Catalyst Family products.
The comparable IEEE standard in use by other manufacturers is GVRP or the more recent MVRP.
Token ring local area network (LAN) technology is a protocol which resides at the data link layer (DLL) of the OSI model. It uses a special three-byte frame called a token that travels around the ring. Token-possession grants the possessor permission to transmit on the medium. Token ring frames travel completely around the loop.
Initially used only in IBM computers, it was eventually standardized with protocol IEEE 802.5.
The data transmission process goes as follows:
The token scheme can also be used with bus topology LANs.
Stations on a token ring LAN are logically organized in a ring topology with data being transmitted sequentially from one ring station to the next with a control token circulating around the ring controlling access. This token passing mechanism is shared by ARCNET, token bus, and FDDI, and has theoretical advantages over the stochastic CSMA/CD of Ethernet.
Physically, a token ring network is wired as a star, with 'hubs' and arms out to each station and the loop going out-and-back through each.
Cabling is generally IBM "Type-1" shielded twisted pair, with unique hermaphroditic connectors, commonly referred to as IBM data connectors in formal writing or
The National Transportation Communications for Intelligent Transportation System Protocol (NTCIP) is a family of standards designed to achieve interoperability and interchangeability between computers and electronic traffic control equipment from different manufacturers.
The protocol is the product of a joint standardization project guided by the Joint Committee on the NTCIP, which is composed of six representatives each from the National Electrical Manufacturers Association (NEMA), the American Association of State Highway and Transportation Officials (AASHTO), and the Institute of Transportation Engineers (ITE). The Joint Committee has in turn formed 14 technical working groups to develop and maintain the standards, and has initiated or produced over 50 standards and information reports.
The project receives funding under a contract with the United States Department of Transportation (USDOT) and is part of a wider effort to develop a comprehensive family of Intelligent Transportation System (ITS) standards.
NEMA initiated the development of the NTCIP in 1992. In early 1993, the US Federal Highway Administration (FHWA) brought together transportation industry representatives to
Econet was Acorn's low-cost local area network system, intended for use by schools and small businesses. Econet is rumoured to be an abbreviation of Economy Network, but Acorn were always careful to stress the Greek root, oikos, meaning "house".
Econet was first introduced for use with the Acorn Atom and Acorn System 2/3/4 computers in 1981. It became popular as a networking system for the BBC Micro and Archimedes computers. The Econet system was eventually supported on all post-Atom Acorn machines except the Electron, the A3010 and the eventually-cancelled Phoebe 2100. The system was supported by Acorn MOS, RISC OS and RISC iX. Acorn received an offer from Commodore International to license the technology, which it refused.
An "Ecolink" interface card for IBM PCs was available. It used Microsoft's MS-NET Redirector for MS-DOS to provide file and printer sharing with the NET USE command.
Acorn Universal Networking (AUN) was an early 1990s implementation of Econet protocols and addressing over TCP/IP, to provide legacy support for Econet on Ethernet-connected machines.
The Econet protocol was also supported by the Linux kernel until May 18, 2012.
Econet is a 5-wire bus network. One
The Exterior Gateway Protocol (EGP) is a now obsolete routing protocol for the Internet originally specified in 1982 by Eric C. Rosen of Bolt, Beranek and Newman, and David L. Mills. It was first described in RFC 827 and formally specified in RFC 904 (1984). Not to be confused with exterior gateway protocols in general (of which EGP and Border Gateway Protocol (BGP) are examples), EGP is a simple reachability protocol, and, unlike modern distance-vector and path-vector protocols, it is limited to tree-like topologies.
During the early days of the Internet, EGP version 3 (EGP3) was used to interconnect autonomous systems. Currently, BGP version 4 is the accepted standard for Internet routing and has essentially replaced the more limited EGP3.
High-Level Data Link Control (HDLC) is a bit-oriented code-transparent synchronous data link layer protocol developed by the International Organization for Standardization (ISO). The original ISO standards for HDLC are:
The current standard for HDLC is ISO 13239, which replaces all of those standards.
HDLC provides both connection-oriented and connectionless service.
HDLC can be used for point to multipoint connections, but is now used almost exclusively to connect one device to another, using what is known as Asynchronous Balanced Mode (ABM). The original master-slave modes Normal Response Mode (NRM) and Asynchronous Response Mode (ARM) are rarely used.
HDLC is based on IBM's SDLC protocol, which is the layer 2 protocol for IBM's Systems Network Architecture (SNA). It was extended and standardized by the ITU as LAP, while ANSI named their essentially identical version ADCCP.
Derivatives have since appeared in innumerable standards. It was adopted into the X.25 protocol stack as LAPB, into the V.42 protocol as LAPM, into the Frame Relay protocol stack as LAPF and into the ISDN protocol stack as LAPD.
HDLC was the inspiration for the IEEE 802.2 LLC protocol, and it is the basis for
Internet Protocol version 4 (IPv4) is the fourth revision in the development of the Internet Protocol (IP) and the first version of the protocol to be widely deployed. Together with IPv6, it is at the core of standards-based internetworking methods of the Internet. As of 2012 IPv4 is still the most widely deployed Internet Layer protocol.
IPv4 is described in IETF publication RFC 791 (September 1981), replacing an earlier definition (RFC 760, January 1980).
IPv4 is a connectionless protocol for use on packet-switched Link Layer networks (e.g., Ethernet). It operates on a best effort delivery model, in that it does not guarantee delivery, nor does it assure proper sequencing or avoidance of duplicate delivery. These aspects, including data integrity, are addressed by an upper layer transport protocol, such as the Transmission Control Protocol (TCP).
IPv4 uses 32-bit (four-byte) addresses, which limits the address space to 4294967296 (2) addresses. Addresses were assigned to users, and the number of unassigned addresses decreased. IPv4 address exhaustion occurred on February 3, 2011. It had been significantly delayed by address changes such as classful network design, Classless
Intermediate System To Intermediate System (IS-IS), usually called is-is, is a routing protocol designed to move information efficiently within a computer network, a group of physically connected computers or similar devices. It accomplishes this by determining the best route for datagrams through a packet-switched network. The protocol was defined in ISO/IEC 10589:2002 as an international standard within the Open Systems Interconnection (OSI) reference design. Though originally an ISO standard, the IETF republished the protocol as an Internet Standard in RFC 1142. IS-IS has been called "the de facto standard for large service provider network backbones."
IS-IS (pronounced "i-s i-s") is an interior gateway protocol, designed for use within an administrative domain or network. This is in contrast to Exterior Gateway Protocols, primarily Border Gateway Protocol (BGP), which is used for routing between autonomous systems (RFC 1930).
IS-IS is a link-state routing protocol, operating by reliably flooding link state information throughout a network of routers. Each IS-IS router independently builds a database of the network's topology, aggregating the flooded network information. Like
9P (or the Plan 9 Filesystem Protocol or Styx) is a network protocol developed for the Plan 9 from Bell Labs distributed operating system as the means of connecting the components of a Plan 9 system. Files are key objects in Plan 9. They represent windows, network connections, processes, and almost anything else available in the operating system. Unlike NFS, 9P encourages caching and also serving synthetic files (e.g. /proc to represent processes).
9P was revised for the 4th edition of Plan 9 under the name 9P2000 that contained various fundamental improvements. The latest version of the Inferno operating system also uses 9P2000. The Inferno file protocol was originally called Styx, but technically it has always been a variant of 9P.
A server implementation of 9P for Unix, called u9fs, is included in the Plan 9 distribution. A kernel client driver for Linux is part of the v9fs project. 9P and its derivatives have also found application in embedded environments, such as the Styx on a Brick project.
Many of Plan 9's applications take the form of 9P servers. Noteworthy examples include:
9P sends the following messages between clients and servers. These messages correspond to the entry
The Digital Audio Access Protocol (DAAP) is the proprietary protocol introduced by Apple in its iTunes software to share media across a local network.
DAAP addresses the same problems for Apple as the UPnP AV standards address for members of the Digital Living Network Alliance (DLNA).
"iTunes Server" is a technical specification that some network-attached storage (NAS) drive manufacturers have included on their devices if they are DAAP enabled. This means the device allows the user to store their iTunes media folder remotely onto the NAS device, whether over a wired connection (such as USB 2.0/3.0, FireWire 400/800, Thunderbolt, etc.), or wirelessly (i.e. over a Wi-Fi connection). However, the DAAP functionality can be limited, as different device manufacturers often will not support all file formats currently supported in iTunes software, when working remotely using DAAP.
The DAAP protocol was originally introduced in iTunes version 4.0. Initially, Apple did not officially release a protocol description, but it has been reverse-engineered to a sufficient degree that reimplementations of the protocol for non-iTunes platforms have been possible. Recently, however, Apple has begun to
SOCKet Secure (SOCKS) is an Internet protocol that routes network packets between a client and server through a proxy server. SOCKS5 additionally provides authentication so only authorized users may access a server. Practically, a SOCKS server will proxy TCP connections to an arbitrary IP address as well as providing a means for UDP packets to be forwarded.
SOCKS performs at Layer 5 of the OSI model—the session layer (an intermediate layer between the presentation layer and the transport layer).
The protocol was originally developed by David Koblas, a system administrator of MIPS Computer Systems. After MIPS was taken over by Silicon Graphics in 1992, Koblas presented a paper on SOCKS at that year's Usenix Security Symposium and SOCKS became publicly available. The protocol was extended to version 4 by Ying-Da Lee of NEC.
The SOCKS reference architecture and client are owned by Permeo Technologies a spin-off from NEC. (Blue Coat Systems bought out Permeo Technologies).
The SOCKS5 protocol was originally a security protocol that made firewalls and other security products easier to administer. It was approved by the IETF in 1996. The protocol was developed in collaboration with
The UNIX System V printing system is one of several standard architectures for printing on the UNIX platform, and is typical of commercial System V-based operating systems such as Solaris and SCO OpenServer. A system running this print architecture could traditionally be identified by the use of the user command lp as the primary interface to the print system, as opposed to the BSD lpr command, though some systems provide lpr as an alias to lp.
Typical user commands available to the SysV print system are:
The original System V printing system remains proprietary; however, the Solaris print system, heavily modified from the original, is open source as part of the OpenSolaris project. The Common Unix Printing System emulates both System V and Berkeley print architectures on the interface level, though its internal architecture is different from both.
Gadu-Gadu (Polish for "chitchat"; commonly known as GG or gg) is a Polish instant messaging client using a proprietary protocol. Gadu-Gadu is the most popular IM service in Poland, with over 15 million registered accounts and approximately 6.5 million users online daily. Gadu-Gadu’s casual gaming portal had some 500,000 active users at the end of March 2009. Users send up to 300 million messages per day.
Gadu-Gadu is financed by the display of advertisements. The developer is based in Warsaw, Poland but the company is wholly owned by the South African media giant Naspers.
Gadu-Gadu uses its own proprietary protocol. As with ICQ, users are identified by unique serial numbers. Protocol's features include status messages, file sharing, and VoIP. Users may format and embed images in messages. Since client version 6.0, an experimental secure connection mode can be used.
The official client provides over 150 emoticons, allows grouping contacts, sending SMS and integrates with other services ran by the same company: a virtual Internet dial-up, a social networking site MojaGeneracja.pl and an internet radio Open.fm.
Gadu-Gadu allows its users to add personal information to a publicly
BACnet is a communications protocol for building automation and control networks. It is an ASHRAE, ANSI, and ISO standard protocol.
BACnet was designed to allow communication of building automation and control systems for applications such as heating, ventilating, and air-conditioning control, lighting control, access control, and fire detection systems and their associated equipment. The BACnet protocol provides mechanisms for computerized building automation devices to exchange information, regardless of the particular building service they perform.
The development of the BACnet protocol began in June, 1987, in Nashville, Tennessee, at the inaugural meeting of the Standard Project Committee (SPC). The committee worked at reaching consensus using working groups to divide up the task of creating a standard. The working groups focused on specific areas and provided information and recommendations to the main committee. The first three working groups were the Data Type and Attribute Working Group, Primitive Data Format Working Group, and the Application Services Working Group.
BACnet became ASHRAE/ANSI Standard 135 in 1995, and ISO 16484-5 in 2003. The Method of Test for Conformance
ICMP Internet Router Discovery Protocol (IRDP) uses Internet Control Message Protocol (ICMP) router advertisements and router solicitation messages to allow a host to discover the addresses of operational routers on the subnet.
It basically consists of 2 Message-Types (see this list) used for discovering local routers. The message type 9 is sent periodically or on request (using a message of type 10) to the local subnet from the local router(s) to propagate themselves. On boot, the client may send a ICMP-Message of type 10 to ask for local routers. When a client receives a message type 9, they add the router to their local routing table.
The Mobile Application Part (MAP) is an SS7 protocol which provides an application layer for the various nodes in GSM and UMTS mobile core networks and GPRS core networks to communicate with each other in order to provide services to mobile phone users. The Mobile Application Part is the application-layer protocol used to access the Home Location Register, Visitor Location Register, Mobile Switching Center, Equipment Identity Register, Authentication Centre, Short message service center and Serving GPRS Support Node (SGSN).
The primary facilities provided by MAP are:
The Mobile Application Part specifications were originally defined by the GSM Association, but are now controlled by ETSI/3GPP. MAP is defined by two different standards, depending upon the mobile network type:
MAP is a Transaction Capabilities Application Part (TCAP) user, and as such can be transported using 'traditional' SS7 protocols or over IP using Transport Independent Signalling Connection Control Part (TI-SCCP); or using SIGTRAN.
In mobile cellular telephony networks like GSM and UMTS the SS7 application MAP is used. Voice connections are Circuit Switched (CS) and data connections are Packet Switched (PS)
The Transmission Control Protocol (TCP) is one of the core protocols of the Internet Protocol Suite. TCP is one of the two original components of the suite, complementing the Internet Protocol (IP), and therefore the entire suite is commonly referred to as TCP/IP. TCP provides reliable, ordered delivery of a stream of octets from a program on one computer to another program on another computer. TCP is the protocol used by major Internet applications such as the World Wide Web, email, remote administration and file transfer. Other applications, which do not require reliable data stream service, may use the User Datagram Protocol (UDP), which provides a datagram service that emphasizes reduced latency over reliability.
In May 1974 the Institute of Electrical and Electronic Engineers (IEEE) published a paper entitled "A Protocol for Packet Network Intercommunication." The paper's authors, Vint Cerf and Bob Kahn, described an internetworking protocol for sharing resources using packet-switching among the nodes. A central control component of this model was the Transmission Control Program that incorporated both connection-oriented links and datagram services between hosts. The
The Kad network is a peer-to-peer (P2P) network which implements the Kademlia P2P overlay protocol. The majority of users on the Kad Network are also connected to servers on the eDonkey network, and Kad Network clients typically query known nodes on the eDonkey network in order to find an initial node on the Kad network.
The Kad network uses a UDP-based protocol to:
Note that the Kad network is not used to actually transfer files across the P2P network. Instead, when a file transfer is initiated, clients connect directly to each other (using the standard public IP network). This traffic is susceptible to blocking/shaping/tracking by your ISP or any other opportunistic middle-man.
As with all decentralized networks, the Kad network requires no official or common servers. As such, it cannot be disabled by shutting down a given subset of key nodes. While the decentralization of the network prevents a simple shut-down, traffic analysis and deep packet inspection will more readily identify the traffic as P2P due to the high variable-destination packet throughput. The large packet volume typically causes a reduction in available CPU and/or network resources usually associated with P2P
The EDonkey Networks (also known as the eDonkey2000 network or eD2k) is a decentralized, mostly server-based, peer-to-peer file sharing network best suited to share big files among users, and to provide long term availability of files. Like most sharing networks, it is decentralized, as there is not any central hub for the network; also, files are not stored on a central server but are exchanged directly between users based on the peer-to-peer principle.
Currently, the eD2k network is not supported by any organization (in the past it was supported by the MetaMachine Corporation, its creator, which now is out of business) and development and maintenance is being fully provided by its community and client developers.
The server part of the network is proprietary freeware. There are two families of server software for the eD2k network: the original one from MetaMachine, written in C++, closed-source and proprietary, and no longer maintained; and eserver, written from scratch by a person named Lugdunum in pure C, also closed-source and proprietary, although available free of charge and for several operating systems and computer architectures. The eserver family is currently in active
The Hypertext Transfer Protocol (HTTP) is an application protocol for distributed, collaborative, hypermedia information systems. HTTP is the foundation of data communication for the World Wide Web.
Hypertext is a multi-linear set of objects, building a network by using logical links (the so-called hyperlinks) between the nodes (e.g. text or words). HTTP is the protocol to exchange or transfer hypertext.
The standards development of HTTP was coordinated by the Internet Engineering Task Force (IETF) and the World Wide Web Consortium (W3C), culminating in the publication of a series of Requests for Comments (RFCs), most notably RFC 2616 (June 1999), which defines HTTP/1.1, the version of HTTP in common use.
HTTP functions as a request-response protocol in the client-server computing model. A web browser, for example, may be the client and an application running on a computer hosting a web site may be the server. The client submits an HTTP request message to the server. The server, which provides resources such as HTML files and other content, or performs other functions on behalf of the client, returns a response message to the client. The response contains completion status
Internet Relay Chat (IRC) is a protocol for real-time Internet text messaging (chat) or synchronous conferencing. It is mainly designed for group communication in discussion forums, called channels, but also allows one-to-one communication via private message as well as chat and data transfer, including file sharing.
IRC was created in 1988. Client software is available for every major operating system that supports Internet access. As of April 2011, the top 100 IRC networks served more than half a million users at a time, with hundreds of thousands of channels operating on a total of roughly 1,500 servers out of roughly 3,200 servers worldwide.
IRC was created by Jarkko Oikarinen in August 1988 to replace a program called MUT (MultiUser Talk) on a BBS called OuluBox in Finland. Oikarinen found inspiration in a chat system known as Bitnet Relay, which operated on the BITNET.
IRC was used to report on the 1991 Soviet coup d'état attempt throughout a media blackout. It was previously used in a similar fashion during the Gulf War. Logs of these and other events are kept in the ibiblio archive.
IRC is an open protocol that uses TCP and, optionally, TLS. An IRC server can connect to
The Signalling Connection Control Part (SCCP) is a network layer protocol that provides extended routing, flow control, segmentation, connection-orientation, and error correction facilities in Signaling System 7 telecommunications networks. SCCP relies on the services of MTP for basic routing and error detection.
The base SCCP specification is defined by the ITU-T, in recommendations Q.711 to Q.714, with additional information to implementors provided by Q.715 and Q.716. There are, however, regional variations defined by local standards bodies. In the United States, ANSI publishes its modifications to Q.713 as ANSI T1.112. The TTC publishes as JT-Q.711 to JT-Q.714, and Europe ETSI publishes ETSI EN 300-009-1: both of which document their modifications to the ITU-T specifications.
Although MTP provides routing capabilities based upon the Point Code, SCCP allows routing using a Point Code and Subsystem number or a Global Title.
A Point Code is used to address a particular node on the network, whereas a Subsystem number addresses a specific application available on that node. SCCP employs a process called Global Title Translation to determine Point Codes from Global Titles so as to
An Internet Protocol address (IP address) is a numerical label assigned to each device (e.g., computer, printer) participating in a computer network that uses the Internet Protocol for communication. An IP address serves two principal functions: host or network interface identification and location addressing. Its role has been characterized as follows: "A name indicates what we seek. An address indicates where it is. A route indicates how to get there."
The designers of the Internet Protocol defined an IP address as a 32-bit number and this system, known as Internet Protocol Version 4 (IPv4), is still in use today. However, due to the enormous growth of the Internet and the predicted depletion of available addresses, a new version of IP (IPv6), using 128 bits for the address, was developed in 1995. IPv6 was standardized as RFC 2460 in 1998, and its deployment has been ongoing since the mid-2000s.
IP addresses are binary numbers, but they are usually stored in text files and displayed in human-readable notations, such as 172.16.254.1 (for IPv4), and 2001:db8:0:1234:0:567:8:1 (for IPv6).
The Internet Assigned Numbers Authority (IANA) manages the IP address space allocations globally
JSON-RPC is a remote procedure call protocol encoded in JSON. It is a very simple protocol (and very similar to XML-RPC), defining only a handful of data types and commands. JSON-RPC allows for notifications (info sent to the server that does not require a response) and for multiple calls to be sent to the server which may be answered out of order.
JSON-RPC works by sending a request to a server implementing this protocol. The client in that case is typically software wanting to call a single method of a remote system. Multiple input parameters can be passed to the remote method as an array or object, whereas the method itself can return multiple output data as well. (This depends on the implemented version.)
A remote method is invoked by sending a request to a remote service using HTTP or a TCP/IP socket (starting with version 2.0). When Using HTTP, the content-type may be defined as application/json.
All transfer types are single objects, serialized using JSON. A request is a call to a specific method provided by a remote system. It must contain three certain properties:
The receiver of the request must reply with a valid response to all received requests. A response must contain
The VT100 is a video terminal that was made by Digital Equipment Corporation (DEC). Its detailed attributes became the de facto standard for terminal emulators to emulate.
It was introduced in August 1978, following its predecessor, the VT52, and communicated with its host system over serial lines using the ASCII character set and control sequences (a.k.a. escape sequences) standardized by ANSI. The VT100 was also the first Digital mass-market terminal to incorporate "graphic renditions" (blinking, bolding, reverse video, and underlining) as well as a selectable 80 or 132 column display. All setup of the VT100 was accomplished using interactive displays presented on the screen; the setup data was stored in non-volatile memory within the terminal. The VT100 also introduced an additional character set that allowed the drawing of on-screen forms.
The control sequences used by the VT100 family are based on the ANSI X3.64 standard, also known as ECMA-48 and ISO/IEC 6429. These are sometimes referred to as ANSI escape codes. The VT100 was not the first terminal to be based on X3.64—The Heath Company had a microprocessor-based video terminal, the Heathkit H-19 (H19), that implemented a
In digital telecommunications, where a single physical wire pair can be used to carry many simultaneous voice conversations by time-division multiplexing, worldwide standards have been created and deployed. The European Conference of Postal and Telecommunications Administrations (CEPT) originally standardized the E-carrier system, which revised and improved the earlier American T-carrier technology, and this has now been adopted by the International Telecommunication Union Telecommunication Standardization Sector (ITU-T). This is now widely used in almost all countries outside the USA, Canada, and Japan.
The E-carrier standards · · form part of the Plesiochronous Digital Hierarchy (PDH) where groups of E1 circuits may be bundled onto higher capacity E3 links between telephone exchanges or countries. This allows a network operator to provide a private end-to-end E1 circuit between customers in different countries that share single high capacity links in between.
In practice, only E1 and E3 versions are used. Physically E1 is transmitted as 32 timeslots and E3 512 timeslots, but one is used for framing and sometimes one allocated for signalling call setup and tear down. Unlike
The Internet Link protocol or IL is a connection-based transport layer protocol designed at Bell Labs originally as part of the Plan 9 operating system and is used to carry 9P. It is assigned the Internet Protocol number of 40. It is similar to TCP but much simpler.
Its main features are:
As of the Fourth Edition of Plan 9, 2003, IL is deprecated in favor of TCP/IP because it doesn't handle long-distance connections well.
IPv6 (Internet Protocol version 6) is the latest revision of the Internet Protocol (IP), the primary communications protocol upon which the entire Internet is built. It is intended to replace the older IPv4, which is still employed for the vast majority of Internet traffic as of 2012. IPv6 was developed by the Internet Engineering Task Force (IETF) to deal with the long-anticipated problem of IPv4 running out of addresses.
Each device on the Internet, such as a computer or mobile telephone, must be assigned a number called an IP address, a binary number with a certain number of digits (each presented by one bit), in order to communicate with other devices. With the ever-increasing number of new devices being connected to the Internet, there is a need for more addresses than IPv4 can accommodate. IPv6 uses 128-bit addresses, allowing for 2, or approximately 3.4×10 addresses — more than 7.9×10 times as many as IPv4, which uses 32-bit addresses. IPv4 allows for only 4,294,967,296 unique addresses worldwide (or less than one address per person alive in 2012), but IPv6 allows for around 4.8×10 addresses per person — a number unlikely ever to run out. However, this means the two
The Gopher protocol ( /ˈɡoʊfər/) is a TCP/IP application layer protocol designed for distributing, searching, and retrieving documents over the Internet. Strongly oriented towards a menu-document design, the Gopher protocol presented an alternative to the World Wide Web in its early stages, but ultimately HTTP became the dominant protocol. The Gopher ecosystem is often regarded as the effective predecessor of the World Wide Web.
Invented by a team led by Mark P. McCahill at the University of Minnesota, the protocol offers some features not natively supported by the Web and imposes a much stronger hierarchy on information stored on it. Its text menu interface is easy to use, and well-suited to computing environments that rely heavily on remote text-oriented computer terminals, which were still common at the time of its creation in 1991, and the simplicity of its protocol facilitated a wide variety of client implementations. More recent Gopher revisions and graphical clients added support for multimedia. Gopher was preferred by many network administrators for using fewer network resources than Web services.
With its hierarchical structure, Gopher provided a useful platform for the
In computing, the Post Office Protocol (POP) is an application-layer Internet standard protocol used by local e-mail clients to retrieve e-mail from a remote server over a TCP/IP connection. POP and IMAP (Internet Message Access Protocol) are the two most prevalent Internet standard protocols for e-mail retrieval. Virtually all modern e-mail clients and servers support both. The POP protocol has been developed through several versions, with version 3 (POP3) being the current standard. Most webmail service providers such as Hotmail, Gmail and Yahoo! Mail also provide IMAP and POP3 service.
POP supports simple download-and-delete requirements for access to remote mailboxes (termed maildrop in the POP RFC's). Although most POP clients have an option to leave mail on server after download, e-mail clients using POP generally connect, retrieve all messages, store them on the user's PC as new messages, delete them from the server, and then disconnect. Other protocols, notably IMAP, (Internet Message Access Protocol) provide more complete and complex remote access to typical mailbox operations. Many e-mail clients support POP as well as IMAP to retrieve messages; however, fewer Internet
BitTorrent is a protocol that underpins the practice of peer-to-peer file sharing and is used for distributing large amounts of data over the Internet. BitTorrent is one of the most common protocols for transferring large files and it has been estimated that, collectively, peer-to-peer networks have accounted for approximately 43% to 70% of all Internet traffic (depending on geographical location) as of February 2009.
Programmer Bram Cohen designed the protocol in April 2001 and released the first available version on July 2, 2001. Currently, numerous BitTorrent clients are available for a variety of computing platforms.
As of January 2012, BitTorrent is utilized by 150 million active users (according to BitTorrent, Inc.). Based on this figure, the total number of monthly BitTorrent users can be estimated at more than a quarter of a billion. At any given instant, BitTorrent has, on average, more active users than YouTube and Facebook combined (this refers to the number of active users at any instant and not to the total number of unique users). Research has also shown that, since 2010, more than 200,000 users of the protocol have been sued.
The BitTorrent protocol can be used to
Digital Access Signalling System 2 (DASS2) is an obsolescent protocol defined by British Telecom for digital links to PSTN based on ISDN. Although still available on request, it has been superseded by ETS 300 102 ("EuroISDN").
DASS2 is an improved version over DASS1, based on experiences with DPNSS.
In the UK, the ISDN concept was first introduced to customers by BT with their DASS2 connections. DASS2 (Digital Access Signalling System) is a BT designed signalling standard. It was introduced before the Q.931 standard was finalised by the International Community. British Telecom used the term ISDN when describing their DASS2 lines.
DASS2 lines are provided to the customer on a 2Mbit/s link and can handle 30 simultaneous calls (64kbit/s each). DASS2 is still offered by BT and other UK carriers. Q.931 is the name of the CCITT document that describes the agreed signalling format for International ISDN. The CCITT used to be International Telegraph and Telephone Consultative Committee. This is the organisation that set out the internationally agreed standards for telecommunications. This organisation has subsequently evolved into the ITU. In the United Kingdom the Q.931 based protocol is
Ethernet /ˈiːθərnɛt/ is a family of computer networking technologies for local area networks (LANs). Ethernet was commercially introduced in 1980 and standardized in 1985 as IEEE 802.3. Ethernet has largely replaced competing wired LAN technologies.
The Ethernet standards comprise several wiring and signaling variants of the OSI physical layer in use with Ethernet. The original 10BASE5 Ethernet used coaxial cable as a shared medium. Later the coaxial cables were replaced by twisted pair and fiber optic links in conjunction with hubs or switches. Data rates were periodically increased from the original 10 megabits per second, to 100 gigabits per second.
Systems communicating over Ethernet divide a stream of data into shorter pieces called frames. Each frame contains source and destination addresses and error-checking data so that damaged data can be detected and re-transmitted. As per the OSI model Ethernet provides services up to and including the data link layer.
Since its commercial release, Ethernet has retained a good degree of compatibility. Features such as the 48-bit MAC address and Ethernet frame format have influenced other networking protocols.
Ethernet was developed at
rsync is a software application and network protocol for Unix-like systems with ports to Windows that synchronizes files and directories from one location to another while minimizing data transfer by using delta encoding when appropriate. Quoting the official website: "rsync is a file transfer program for Unix systems. rsync uses the 'rsync algorithm' which provides a very fast method for bringing remote files into sync." An important feature of rsync not found in most similar programs/protocols is that the mirroring takes place with only one transmission in each direction. rsync can copy or display directory contents and copy files, optionally using compression and recursion.
In daemon mode, rsync listens on the default TCP port of 873, serving files in the native rsync protocol or via a remote shell such as RSH or SSH. In the latter case, the rsync client executable must be installed on the remote machine as well as on the local machine.
Released under the GNU General Public License version 3, rsync is free software. It is widely used.
Andrew Tridgell and Paul Mackerras wrote the original rsync. Tridgell discusses the design, implementation and performance of rsync in chapters 3
FastTrack is a peer-to-peer (P2P) protocol that was used by the Kazaa, Grokster, iMesh, and Morpheus file sharing programs. FastTrack was the most popular file sharing network in 2003, and used mainly for the exchange of music mp3 files. The network had approximately 2.4 million concurrent users in 2003. It is estimated that the total number of users was greater than that of Napster at its peak.
The FastTrack protocol and Kazaa were created and developed by Estonian programmers of BlueMoon Interactive headed by Jaan Tallinn, the same team that later created Skype. After selling it to Niklas Zennström from Sweden and Janus Friis from Denmark, it was introduced in March 2001 by their Dutch company Consumer Empowerment. It appeared during the end of the first generation of P2P networks – Napster shut down in July of that year.
There are three FastTrack-based networks, and they use mutually incompatible versions of the protocol. The most popular clients on each are Kazaa (and its variations), Grokster, and iMesh.
For more information about the various lawsuits surrounding Kazaa and Sharman Networks, see Kazaa.
FastTrack uses supernodes to improve scalability.
To allow downloading from
Sinec H1 is an Ethernet-based protocol that provides the transport layer function. The protocol was developed by Siemens and is used mainly for control applications. It has large bandwidth and is well suited to the transmission of large volumes of data.
AOL Instant Messenger (AIM) is an instant messaging and presence computer program which uses the proprietary OSCAR instant messaging protocol and the TOC protocol to allow registered users to communicate in real time. It was released by AOL in May 1997. Stand-alone official AIM client software includes advertisements and is available for Microsoft Windows, Windows Mobile, Mac OS, Mac OS X, Android, iOS, BlackBerry OS. The software, maintained by AOL, Inc., at one time had the largest share of the instant messaging market in North America, especially in the United States (with 52% of the total reported as of 2006). This does not include other instant messaging software related to or developed by AOL, such as ICQ and iChat. As of June 2011, one reported market share had collapsed to 0.73%. However, this number only reflects installed IM applications, and not active users.
The standard protocol that AIM clients use to communicate is called Open System for CommunicAtion in Realtime (OSCAR). Most AOL-produced versions of AIM and popular third party AIM clients use this protocol. However, AOL also created a simpler protocol called TOC that lacks many of OSCAR's features but is sometimes
IEEE 802.16 is a series of Wireless Broadband standards authored by the Institute of Electrical and Electronics Engineers (IEEE). The IEEE Standards Board established a working group in 1999 to develop standards for broadband for Wireless Metropolitan Area Networks. The Workgroup is a unit of the IEEE 802 local area network and metropolitan area network standards committee.
Although the 802.16 family of standards is officially called WirelessMAN in IEEE, it has been commercialized under the name “WiMAX” (from "Worldwide Interoperability for Microwave Access") by the WiMAX Forum industry alliance. The Forum promotes and certifies compatibility and interoperability of products based on the IEEE 802.16 standards.
The 802.16e-2005 amendment version was announced as being deployed around the world in 2009. The version IEEE 802.16-2009 was amended by IEEE 802.16j-2009.
Projects publish draft and proposed standards with the letter "P" prepended, which gets dropped and replaced by a dash and year when the standards are ratified and published.
IEEE 802.16 standardizes the air interface and related functions associated with wireless local loop. The charter originally envisioned that three
Internet Protocol Security (IPsec) is a protocol suite for securing Internet Protocol (IP) communications by authenticating and encrypting each IP packet of a communication session. IPsec also includes protocols for establishing mutual authentication between agents at the beginning of the session and negotiation of cryptographic keys to be used during the session.
IPsec is an end-to-end security scheme operating in the Internet Layer of the Internet Protocol Suite. It can be used in protecting data flows between a pair of hosts (host-to-host), between a pair of security gateways (network-to-network), or between a security gateway and a host (network-to-host).
Some other Internet security systems in widespread use, such as Secure Sockets Layer (SSL), Transport Layer Security (TLS) and Secure Shell (SSH), operate in the upper layers of the TCP/IP model. In the past, the use of TLS/SSL had to be designed into an application to protect the application protocols. In contrast, since day one, applications did not need to be specifically designed to use IPsec. Hence, IPsec protects any application traffic across an IP network. This holds true now for SSL as well with the rise of SSL based
Modbus is a serial communications protocol published by Modicon in 1979 for use with its programmable logic controllers (PLCs). Simple and robust, it has since become a de facto standard communication protocol, and it is now amongst the most commonly available means of connecting industrial electronic devices. The main reasons for the use of Modbus in the industrial environment are:
Modbus allows for communication between many (approximately 240) devices connected to the same network, for example a system that measures temperature and humidity and communicates the results to a computer. Modbus is often used to connect a supervisory computer with a remote terminal unit (RTU) in supervisory control and data acquisition (SCADA) systems. Many of the data types are named from its use in driving relays: a single-bit physical output is called a coil, and a single-bit physical input is called a discrete input or a contact.
The development and update of Modbus protocols are managed by the Modbus Organization, formed of independent users and suppliers of Modbus compliant devices.
Versions of the Modbus protocol exist for serial port and for Ethernet and other networks that support the
The Apple Filing Protocol (AFP), formerly AppleTalk Filing Protocol, is a proprietary network protocol that offers file services for Mac OS X and original Mac OS. In Mac OS X, AFP is one of several file services supported including Server Message Block (SMB), Network File System (NFS), File Transfer Protocol (FTP), and WebDAV. AFP currently supports Unicode file names, POSIX and access control list permissions, resource forks, named extended attributes, and advanced file locking. In Mac OS 9 and earlier, AFP was the primary protocol for file services.
AFP versions 3.0 and greater rely exclusively on TCP/IP (port 548 or 427) for establishing communication, supporting AppleTalk only as a service discovery protocol. The AFP 2.x family supports both TCP/IP (using Data Stream Interface) and AppleTalk for communication and service discovery. Many third-party AFP implementations use AFP 2.x, thereby supporting AppleTalk as a connection method. Still earlier versions rely exclusively on AppleTalk. For this reason, some older literature refers to AFP as "AppleTalk Filing Protocol". Other literature may refer to AFP as "AppleShare," the name of the Mac OS 9 (and earlier) AFP client.
SILC (Secure Internet Live Conferencing protocol) is a protocol that provides secure synchronous conferencing services (very much like IRC) over the Internet.
The SILC protocol can be divided in three main parts: SILC Key Exchange (SKE) protocol, SILC Authentication protocol and SILC Packet protocol. SILC protocol additionally defines SILC Commands that are used to manage the SILC session. SILC provides channels (groups), nicknames, private messages, and other common features. However, SILC nicknames, in contrast to many other protocols (e.g. IRC), are not unique; a user is able to use any nickname, even if one is already in use. The real identification in the protocol is performed by unique Client ID . The SILC protocol uses this to overcome nickname collision, a problem present in many other protocols. All messages sent in a SILC network are binary, allowing them to contain any type of data, including text, video, audio, and other multimedia data. The SKE protocol is used to establish session key and other security parameters for protecting the SILC Packet protocol. The SKE itself is based on the Diffie-Hellman key exchange algorithm (a form of asymmetric cryptography) and the
Simple Mail Transfer Protocol (SMTP) is an Internet standard for electronic mail (e-mail) transmission across Internet Protocol (IP) networks. SMTP was first defined by RFC 821 (1982, eventually declared STD 10), and last updated by RFC 5321 (2008) which includes the extended SMTP (ESMTP) additions, and is the protocol in widespread use today. SMTP uses TCP port 25. The protocol for new submissions (MSA) is effectively the same as SMTP, but it uses port 587 instead. SMTP connections secured by SSL are known by the shorthand SMTPS, though SMTPS is not a protocol in its own right.
While electronic mail servers and other mail transfer agents use SMTP to send and receive mail messages, user-level client mail applications typically only use SMTP for sending messages to a mail server for relaying. For receiving messages, client applications usually use either the Post Office Protocol (POP) or the Internet Message Access Protocol (IMAP) or a proprietary system (such as Microsoft Exchange or Lotus Notes/Domino) to access their mail box accounts on a mail server.
Various forms of one-to-one electronic messaging were used in the 1960s. People communicated with one another using systems
X.25 is an ITU-T standard protocol suite for packet switched wide area network (WAN) communication. An X.25 WAN consists of packet-switching exchange (PSE) nodes as the networking hardware, and leased lines, plain old telephone service connections or ISDN connections as physical links. X.25 is a family of protocols that was popular during the 1980s with telecommunications companies and in financial transaction systems such as automated teller machines. X.25 was originally defined by the International Telegraph and Telephone Consultative Committee (CCITT, now ITU-T) in a series of drafts and finalized in a publication known as The Orange Book in 1976.
While X.25 has been, to a large extent, replaced by less complex protocols, especially the Internet protocol (IP), the service is still used and available in niche and legacy applications.
X.25 is one of the oldest packet-switched services available. It was developed before the OSI Reference Model. The protocol suite is designed as three conceptual layers, which correspond closely to the lower three layers of the seven-layer OSI model. It also supports functionality not found in the OSI network layer.
X.25 was developed in the ITU-T
Amazon S3 (Simple Storage Service) is an online storage web service offered by Amazon Web Services. Amazon S3 provides storage through web services interfaces (REST, SOAP, and BitTorrent). Amazon launched S3, its first publicly available web service, in the United States in March 2006 and in Europe in November 2007.
At its inception, Amazon charged end users US$0.15 per gigabyte-month, with additional charges for bandwidth used in sending and receiving data, and a per-request (get or put) charge. As of November 1, 2008, pricing moved to tiers where end users storing more than 50 terabytes receive discounted pricing. Amazon claims that S3 uses the same scalable storage infrastructure that Amazon.com uses to run its own global e-commerce network.
Amazon S3 is reported to store more than a trillion objects as of June 2012. This is up from 102 billion objects as of March 2010, 64 billion objects in August 2009, 52 billion in March 2009, 29 billion in October 2008, 14 billion in January 2008, and 10 billion in October 2007. S3 uses include web hosting, image hosting, and storage for backup systems. S3 comes with a 99.9% monthly uptime guarantee which equates to approximately 43 minutes
Extensible Messaging and Presence Protocol (XMPP) is a communications protocol for message-oriented middleware based on XML (Extensible Markup Language). The protocol was originally named Jabber, and was developed by the Jabber open-source community in 1999 for near-real-time, instant messaging (IM), presence information, and contact list maintenance. Designed to be extensible, the protocol has also been used for publish-subscribe systems; signalling for VoIP, video, and file transfer; gaming; Internet of Things applications such as the smart grid; and Social networking services.
Unlike most instant messaging protocols, XMPP is defined in an open standard and uses an open systems approach of development and application, by which anyone may implement an XMPP service and interoperate with other organizations' implementations. Because XMPP is an open protocol, implementations can be developed using any software license; although many server, client, and library implementations are distributed as free and open-source software, numerous freeware and commercial software implementations also exist.
The Internet Engineering Task Force (IETF) formed an XMPP working group in 2002 to
Kerberos ( /ˈkɛərbərəs/) is a computer network authentication protocol which works on the basis of "tickets" to allow nodes communicating over a non-secure network to prove their identity to one another in a secure manner. Its designers aimed primarily at a client–server model, and it provides mutual authentication—both the user and the server verify each other's identity. Kerberos protocol messages are protected against eavesdropping and replay attacks. Kerberos builds on symmetric key cryptography and requires a trusted third party, and optionally may use public-key cryptography by utilizing asymmetric key cryptography during certain phases of authentication. Kerberos uses port 88 by default.
MIT developed Kerberos to protect network services provided by Project Athena. The protocol was named after the character Kerberos (or Cerberus) from Greek mythology which was a monstrous three-headed guard dog of Hades. Several versions of the protocol exist; versions 1–3 occurred only internally at MIT.
Steve Miller and Clifford Neuman, the primary designers of Kerberos version 4, published that version in the late 1980s, although they had targeted it primarily for Project Athena.
Secure Shell (SSH) is a cryptographic network protocol for secure data communication, remote shell services or command execution and other secure network services between two networked computers that it connects via a secure channel over an insecure network: a server and a client (running SSH server and SSH client programs, respectively). The protocol specification distinguishes two major versions that are referred to as SSH-1 and SSH-2.
The best-known application of the protocol is for access to shell accounts on Unix-like operating systems (it can be used in a similar fashion for accounts on Windows, though that is not a very popular option due to RDP/Terminal Server). It was designed as a replacement for Telnet and other insecure remote shell protocols such as the Berkeley rsh and rexec protocols, which send information, notably passwords, in plaintext, rendering them susceptible to interception and disclosure using packet analysis. The encryption used by SSH is intended to provide confidentiality and integrity of data over an unsecured network, such as the Internet.
SSH uses public-key cryptography to authenticate the remote computer and allow it to authenticate the user, if
Abstract Syntax Notation One (ASN.1) is a standard and flexible notation that describes rules and structures for representing, encoding, transmitting, and decoding data in telecommunications and computer networking. The formal rules enable representation of objects that are independent of machine-specific encoding techniques. Formal notation makes it possible to automate the task of validating whether a specific instance of data representation abides by the specifications. In other words, software tools can be used for the validation.
ASN.1 is a joint standard of the International Organization for Standardization (ISO), International Electrotechnical Commission (IEC), and International Telecommunication Union Telecommunication Standardization Sector ITU-T, originally defined in 1984 as part of CCITT X.409:1984. ASN.1 moved to its own standard, X.208, in 1988 due to wide applicability. The substantially revised 1995 version is covered by the X.680 series. The latest available version is dated 2008, and is backward compatible with the 1995 version.
Data generated at various sources of observation need to be transmitted to one or more locations that process it to generate useful
Real Time Messaging Protocol (RTMP) was initially a proprietary protocol developed by Macromedia for streaming audio, video and data over the Internet, between a Flash player and a server. Macromedia is now owned by Adobe, which has released an incomplete version of the specification of the protocol for public use.
The RTMP protocol has multiple variations:
While the primary motivation for RTMP was to be a protocol for playing Flash video, it is also used in some other applications, such as the Adobe LiveCycle Data Services ES.
RTMP (except RTMFP) is a TCP-based protocol which maintains persistent connections and allows low-latency communication. To deliver streams smoothly and transmit as much information as possible, it splits streams into fragments and their size is negotiated dynamically between the client and server while sometimes it is kept unchanged: the default fragment sizes are 64-bytes for audio data, and 128 bytes for video data and most other data types. Fragments from different streams may then be interleaved, and multiplexed over a single connection. With longer data chunks the protocol thus carries only a one-byte header per fragment, so incurring very little
RSS Rich Site Summary (originally RDF Site Summary, often dubbed Really Simple Syndication) is a family of web feed formats used to publish frequently updated works—such as blog entries, news headlines, audio, and video—in a standardized format. An RSS document (which is called a "feed", "web feed", or "channel") includes full or summarized text, plus metadata such as publishing dates and authorship.
RSS feeds benefit publishers by letting them syndicate content automatically. A standardized XML file format allows the information to be published once and viewed by many different programs. They benefit readers who want to subscribe to timely updates from favorite websites or to aggregate feeds from many sites into one place.
RSS feeds can be read using software called an "RSS reader", "feed reader", or "aggregator", which can be web-based, desktop-based, or mobile-device-based. The user subscribes to a feed by entering into the reader the feed's URI or by clicking a feed icon in a web browser that initiates the subscription process. The RSS reader checks the user's subscribed feeds regularly for new work, downloads any updates that it finds, and provides a user interface to monitor
The Dynamic Host Configuration Protocol (DHCP) is a network protocol that is used to configure network devices so that they can communicate on an IP network. A DHCP client uses the DHCP protocol to acquire configuration information, such as an IP address, a default route and one or more DNS server addresses from a DHCP server. The DHCP client then uses this information to configure its host. Once the configuration process is complete, the host is able to communicate on the internet.
The DHCP server maintains a database of available IP addresses and configuration information. When it receives a request from a client, the DHCP server determines the network to which the DHCP client is connected, and then allocates an IP address or prefix that is appropriate for the client, and sends configuration information appropriate for that client.
Because the DHCP protocol must work correctly even before DHCP clients have been configured, the DHCP server and DHCP client must be connected to the same network link. In larger networks, this is not practical. On such networks, each network link contains one or more DHCP relay agents. These DHCP relay agents receive messages from DHCP clients and
MIDI ( /ˈmɪdi/; short for Musical Instrument Digital Interface) is an electronic musical instrument industry specification that enables a wide variety of digital musical instruments, computers and other related devices to connect and communicate with one another. It is a set of standard commands that allows electronic musical instruments, performance controllers, computers and related devices to communicate, as well as a hardware standard that guarantees compatibility between them. MIDI equipment captures note events and adjustments to controls such as knobs and buttons, encodes them as digital messages, and sends these messages to other devices where they control sound generation and other features. This data can be recorded into a hardware or software device called a sequencer, which can be used to edit the data and to play it back at a later time. MIDI carries note event messages that specify notation, pitch and velocity, control signals for parameters such as volume, vibrato, audio panning and cues, and clock signals that set and synchronize tempo between multiple devices. A single MIDI link can carry up to sixteen channels of information, each of which can be routed to a
Network Time Protocol (NTP) is a networking protocol for clock synchronization between computer systems over packet-switched, variable-latency data networks.
In operation since before 1985, NTP is one of the oldest Internet protocols in use. NTP was originally designed by David L. Mills of the University of Delaware, who still develops and maintains it with a team of volunteers.
NTP provides Coordinated Universal Time (UTC) including scheduled leap second adjustments. No information about time zones or daylight saving time is transmitted; this information is outside its scope and must be obtained separately.
NTP uses Marzullo's algorithm and is designed to resist the effects of variable latency. NTP can usually maintain time to within tens of milliseconds over the public Internet, and can achieve 1 millisecond accuracy in local area networks under ideal conditions.
As of June 2010, the current reference implementation is version 4 (NTPv4), which is a proposed standard as documented in RFC 5905. It succeeds version 3, specified in RFC 1305.
The protocol uses the User Datagram Protocol (UDP) on port number 123.
A less complex implementation of NTP, using the same protocol but without
Remote Authentication Dial In User Service (RADIUS) is a networking protocol that provides centralized Authentication, Authorization, and Accounting (AAA) management for computers to connect and use a network service. RADIUS was developed by Livingston Enterprises, Inc., in 1991 as an access server authentication and accounting protocol and later brought into the Internet Engineering Task Force (IETF) standards.
Because of the broad support and the ubiquitous nature of the RADIUS protocol, it is often used by ISPs and enterprises to manage access to the Internet or internal networks, wireless networks, and integrated e-mail services. These networks may incorporate modems, DSL, access points, VPNs, network ports, web servers, etc.
RADIUS is a client/server protocol that runs in the application layer, using UDP as transport. The Remote Access Server, the Virtual Private Network server, the Network switch with port-based authentication, and the Network Access Server (NAS), are all gateways that control access to the network, and all have a RADIUS client component that communicates with the RADIUS server. The RADIUS server is usually a background process running on a UNIX or Microsoft
The Routing Information Protocol (RIP) is a distance-vector routing protocol, which employs the hop count as a routing metric. RIP prevents routing loops by implementing a limit on the number of hops allowed in a path from the source to a destination. The maximum number of hops allowed for RIP is 15. This hop limit, however, also limits the size of networks that RIP can support. A hop count of 16 is considered an infinite distance and used to deprecate inaccessible, inoperable, or otherwise undesirable routes in the selection process.
RIP implements the split horizon, route poisoning and holddown mechanisms to prevent incorrect routing information from being propagated. These are some of the stability features of RIP. It is also possible to use the so called RMTI (Routing Information Protocol with Metric-based Topology Investigation) algorithm to cope with the count-to-infinity problem. With its help, it is possible to detect every possible loop with a very small computation effort.
Originally each RIP router transmitted full updates every 30 seconds. In the early deployments, routing tables were small enough that the traffic was not significant. As networks grew in size, however,
UDP hole punching is a commonly used technique employed in network address translator (NAT) applications for maintaining User Datagram Protocol (UDP) packet streams that traverse the NAT. NAT traversal techniques are typically required for client-to-client networking applications on the Internet involving hosts connected in private networks, especially in peer-to-peer and Voice over Internet Protocol (VoIP) deployments.
UDP hole punching establishes connectivity between two hosts communicating across one or more network address translators. Typically, third party hosts on the public transit network are used to establish UDP port states that may be used for direct communications between the communicating hosts. Once port state has been successfully established and the hosts are communicating, port state may be maintained by either normal communications traffic, or in the prolonged absence thereof, by so called keep-alive packets, usually consisting of empty UDP packets or packets with minimal non-intrusive content.
UDP hole punching is a method for establishing bidirectional UDP connections between Internet hosts in private networks using network address translators. The technique
Border Gateway Protocol (BGP) is the protocol which makes core routing decisions on the Internet. It maintains a table of IP networks or 'prefixes' which designate network reach-ability among autonomous systems (AS). It is described as a path vector protocol. BGP does not use traditional Interior Gateway Protocol (IGP) metrics, but makes routing decisions based on path, network policies and/or rule-sets. For this reason, it is more appropriately termed a reach-ability protocol rather than routing protocol.
BGP was created to replace the Exterior Gateway Protocol (EGP) to allow fully decentralized routing in order to transition from the core ARPAnet model to a decentralized system that included the NSFNET backbone and its associated regional networks. This allowed the Internet to become a truly decentralized system. Since 1994, version four of the BGP has been in use on the Internet. All previous versions are now obsolete. The major enhancement in version 4 was support of Classless Inter-Domain Routing and use of route aggregation to decrease the size of routing tables. Since January 2006, version 4 is codified in RFC 4271, which went through more than 20 drafts based on the earlier
The Dynamic Trunking Protocol (DTP) is a proprietary networking protocol developed by Cisco Systems for the purpose of negotiating trunking on a link between two VLAN-aware switches, and for negotiating the type of trunking encapsulation to be used. It works on the Layer 2 of the OSI model. VLAN trunks formed using DTP may utilize either IEEE 802.1Q or Cisco ISL trunking protocols.
DTP should not be confused with VTP, as they serve different purposes. VTP communicates VLAN existence information between switches. DTP aids with trunk port establishment. Neither protocol transmits the data frames that trunks carry.
The following switch port mode settings exist:
FTPS (also known as FTP-ES, FTP-SSL and FTP Secure) is an extension to the commonly used File Transfer Protocol (FTP) that adds support for the Transport Layer Security (TLS) and the Secure Sockets Layer (SSL) cryptographic protocols.
FTPS should not be confused with the SSH File Transfer Protocol (SFTP), an incompatible secure file transfer subsystem for the Secure Shell (SSH) protocol. It is also different from Secure FTP, the practice of tunneling FTP through an SSH connection.
The File Transfer Protocol was drafted in 1971 for use with the scientific and research network, ARPANET. Access to the ARPANET during this time was limited to a small number of military sites and universities and a narrow community of users who could operate without data security or privacy requirements within the protocol.
As the ARPANET gave way to the NSFnet and then the Internet, a broader population potentially had access to the data as it traversed increasingly longer paths from client to server. The opportunity for unauthorized third parties to eavesdrop on data transmissions increased proportionally.
In 1994, the internet browser company Netscape developed and released the application layer
IEEE 802.11 is a set of standards for implementing wireless local area network (WLAN) computer communication in the 2.4, 3.6 and 5 GHz frequency bands. They are created and maintained by the IEEE LAN/MAN Standards Committee (IEEE 802). The base version of the standard IEEE 802.11-2012 has had subsequent amendments. These standards provide the basis for wireless network products using the Wi-Fi brand.
The 802.11 family consists of a series of half-duplex over-the-air modulation techniques that use the same basic protocol. The most popular are those defined by the 802.11b and 802.11g protocols, which are amendments to the original standard. 802.11-1997 was the first wireless networking standard, but 802.11b was the first widely accepted one, followed by 802.11g and 802.11n. 802.11n is a new multi-streaming modulation technique. Other standards in the family (c–f, h, j) are service amendments and extensions or corrections to the previous specifications.
802.11b and 802.11g use the 2.4 GHz ISM band, operating in the United States under Part 15 of the US Federal Communications Commission Rules and Regulations. Because of this choice of frequency band, 802.11b and g equipment may
Asynchronous Transfer Mode (ATM) is, according to the ATM Forum, "a telecommunications concept defined by ANSI and ITU (formerly CCITT) standards for carriage of a complete range of user traffic, including voice, data, and video signals," and is designed to unify telecommunication and computer networks. It uses asynchronous time-division multiplexing, and it encodes data into small, fixed-sized cells. This differs from approaches such as the Internet Protocol or Ethernet that use variable sized packets or frames. ATM provides data link layer services that run over a wide range of OSI physical Layer links. ATM has functional similarity with both circuit switched networking and small packet switched networking. It was designed for a network that must handle both traditional high-throughput data traffic (e.g., file transfers), and real-time, low-latency content such as voice and video. ATM uses a connection-oriented model in which a virtual circuit must be established between two endpoints before the actual data exchange begins. ATM is a core protocol used over the SONET/SDH backbone of the public switched telephone network (PSTN) and Integrated Services Digital Network (ISDN), but
In computer networking, the Bootstrap Protocol, or BOOTP, is a network protocol used by a network client to obtain an IP address from a configuration server. The BOOTP protocol was originally defined in RFC 951.
BOOTP is usually used during the bootstrap process when a computer is starting up. A BOOTP configuration server assigns an IP address to each client from a pool of addresses. BOOTP uses the User Datagram Protocol (UDP) as a transport on IPv4 networks only.
Historically, BOOTP has also been used for Unix-like diskless workstations to obtain the network location of their boot image in addition to an IP address, and also by enterprises to roll out a pre-configured client (e.g., Windows) installation to newly installed PCs.
Originally requiring the use of a boot floppy disk to establish the initial network connection, manufacturers of network cards later embedded the protocol in the BIOS of the interface cards as well as system boards with on-board network adapters, thus allowing direct network booting.
In 2005, users with an interest in diskless stand-alone media center PCs have shown new interest in this method of booting a Windows operating system.
The Dynamic Host
In computer networking, the Name/Finger protocol and the Finger user information protocol are simple network protocols for the exchange of human-oriented status and user information.
The Name/Finger protocol, written by David Zimmerman, is based on Request for comments document RFC 742 (December 1977) as an interface to the name and finger programs that provide status reports on a particular computer system or a particular person at network sites. The finger program was written in 1971 by Les Earnest who created the program to solve the need of users who wanted information on other users of the network. Information on who is logged-in was useful to check the availability of a person to meet. This was probably the earliest form of presence information for remote network users.
Prior to the finger program, the only way to get this information was with a who program that showed IDs and terminal line numbers for logged-in users. Earnest named his program after the idea that people would run their fingers down the who list to find what they were looking for.
The finger daemon runs on TCP port 79. The client will (in the case of remote hosts) open a connection to port 79. An RUIP (Remote
The Network Information Service, or NIS (originally called Yellow Pages or YP) is a client–server directory service protocol for distributing system configuration data such as user and host names between computers on a computer network. Sun Microsystems developed the NIS; the technology is licensed to virtually all other Unix vendors.
Because British Telecom PLC owned the name "Yellow Pages" as a registered trademark in the United Kingdom for its paper-based, commercial telephone directory, Sun changed the name of its system to NIS, though all the commands and functions still start with “yp”.
An NIS/YP system maintains and distributes a central directory of user and group information, hostnames, e-mail aliases and other text-based tables of information in a computer network. For example, in a common UNIX environment, the list of users for identification is placed in /etc/passwd, and secret authentication hashes in /etc/shadow. NIS adds another “global” user list which is used for identifying users on any client of the NIS domain.
Administrators have the ability to configure NIS to serve password data to outside processes to authenticate users using various versions of the Unix
The Message Transfer Part (MTP) is part of the Signaling System 7 (SS7) used for communication in Public Switched Telephone Networks. MTP is responsible for reliable, unduplicated and in-sequence transport of SS7 messages between communication partners.
MTP is formally defined primarily in ITU-T recommendations Q.701, Q.702, Q.703, Q.704 and Q.705. Tests for the MTP are specified in the ITU-T recommendations Q.781 for MTP2 and in Q.782 for MTP3. These tests are used to validate the correct implementation of the MTP protocol.
Different countries use different variants of the MTP protocols. In North America, the formal standard followed is ANSI T1.111. In Europe, national MTP protocols are based on ETSI EN 300-008-1.
The SS7 stack can be separated into four functional levels:
Level 1 through Level 3 comprise the MTP, and Level 4 the MTP user. MTP Level 3 is sometimes abbreviated MTP3; MTP Level 2, MTP2. MTP and SCCP are together referred to as the Network Service Part (NSP).
There is no one-to-one mapping of MTP Levels 1 through 3 onto the OSI model. Instead, MTP provides the functionality of layers 1, 2 and part of layer 3 in the OSI model. The part of layer 3 of the OSI model that
Microsoft Notification Protocol (MSNP, also known as the Mobile Status Notification Protocol) is an instant messaging protocol developed by Microsoft for use by the Microsoft Messenger service and the instant messaging clients that connect to it, such as Windows Live Messenger, its earlier incarnations MSN Messenger and Windows Messenger, and Microsoft Messenger for Mac. Third-party clients such as Pidgin and Trillian can also communicate using the protocol. MSNP was first used in a publicly available product with the first release of MSN Messenger in 1999.
Any major change made to the protocol, such as a new command or syntax changes, results in a version-number incremented by one in the format of MSNP#. During October 2003, Microsoft started blocking access to Messenger service using versions below MSNP8.
Starting on 2007-09-11, Microsoft forces most current users of MSN Messenger to upgrade to Windows Live Messenger 8.1 due to security considerations. Noticing that Microsoft may end support for the older versions of MSNP in the near future, open source implementations of the protocol (mostly based on MSNP8) now have to consider changing to MSNP13-15. This will require lots of
REpresentational State Transfer (REST) is a style of software architecture for distributed systems such as the World Wide Web. REST has emerged as a predominant Web service design model.
The term representational state transfer was introduced and defined in 2000 by Roy Fielding in his doctoral dissertation. Fielding is one of the principal authors of the Hypertext Transfer Protocol (HTTP) specification versions 1.0 and 1.1.
Conforming to the REST constraints is generally referred to as being "RESTful".
The REST architectural style was developed in parallel with HTTP/1.1, based on the existing design of HTTP/1.0. The largest implementation of a system conforming to the REST architectural style is the World Wide Web. REST exemplifies how the Web's architecture emerged by characterizing and constraining the macro-interactions of the four components of the Web, namely origin servers, gateways, proxies and clients, without imposing limitations on the individual participants. As such, REST essentially governs the proper behavior of participants.
REST-style architectures consist of clients and servers. Clients initiate requests to servers; servers process requests and return appropriate
Interior Gateway Routing Protocol (IGRP) is a distance vector interior routing protocol (IGP) invented by Cisco. It is used by routers to exchange routing data within an autonomous system.
IGRP is a proprietary protocol. IGRP was created in part to overcome the limitations of RIP (maximum hop count of only 15, and a single routing metric) when used within large networks. IGRP supports multiple metrics for each route, including bandwidth, delay, load, MTU, and reliability; to compare two routes these metrics are combined together into a single metric, using a formula which can be adjusted through the use of pre-set constants. The maximum hop count of IGRP-routed packets is 255 (default 100), and routing updates are broadcast every 90 seconds (by default).
IGRP is considered a classful routing protocol. Because the protocol has no field for a subnet mask, the router assumes that all subnetwork addresses within the same Class A, Class B, or Class C network have the same subnet mask as the subnet mask configured for the interfaces in question. This contrasts with classless routing protocols that can use variable length subnet masks. Classful protocols have become less popular as they
The V.23 standard was an early modem standard approved by the ITU in 1988. It specifies audio frequency-shift keying (AFSK) to encode and transfer data at a rate of 1200 bits per second, half-duplex at 1200 baud (Mode 2), (or at a "fallback rate" of 600 baud, mode 1) for the forward data-transmission channel, and an optional 75 baud backward channel.
In some European countries,(and perhaps elsewhere), V.23 Mode 2 AFSK modulation, (without the backward channel) is used to transmit Caller ID information over POTS lines in the public telephone network.
The 75 baud backward channel was originally envisioned for use in error correction schemes, but V.23 was also widely used in Videotex applications where the backward channel was used to sent keyboard data in an asymmetrical full duplex scheme.
The BELL 202 communications standard defines a similar modulation scheme.
L2F, or Layer 2 Forwarding, is a tunneling protocol developed by Cisco Systems, Inc. to establish virtual private network connections over the Internet. L2F does not provide encryption or confidentiality by itself; It relies on the protocol being tunneled to provide privacy. L2F was specifically designed to tunnel Point-to-Point Protocol (PPP) traffic.
Virtual dial-up allows many separate and autonomous protocol domains to share common access infrastructure including modems, Access Servers, and ISDN routers. RFCs prior to 2341 have specified protocols for supporting IP dial-up via SLIP and multiprotocol dial-up via PPP.
Multipurpose Internet Mail Extensions (MIME) is an Internet standard that extends the format of email to support:
MIME's use, however, has grown beyond describing the content of email to describe content type in general, including for the web (see Internet media type) and as a storage for rich content in some commercial products (e.g., IBM Lotus Domino and IBM Lotus Quickr).
Virtually all human-written Internet email and a fairly large proportion of automated email is transmitted via SMTP in MIME format. Internet email is so closely associated with the SMTP and MIME standards that it is sometimes called SMTP/MIME email.
The content types defined by MIME standards are also of importance outside of email, such as in communication protocols like HTTP for the World Wide Web. HTTP requires that data be transmitted in the context of email-like messages, although the data most often is not actually email.
MIME is specified in six linked RFC memoranda: RFC 2045, RFC 2046, RFC 2047, RFC 4288, RFC 4289 and RFC 2049, which together define the specifications.
The basic Internet email transmission protocol, SMTP, supports only 7-bit ASCII characters (see also 8BITMIME). This effectively limits
MSN Messenger, now called Windows Live Messenger, is a freeware instant messaging client that was developed and distributed by Microsoft in 1999 to 2005 and in 2007 for computers running the Microsoft Windows operating system (except Windows Vista), and aimed towards home users. It was renamed Windows Live Messenger in February 2006 as part of Microsoft's Windows Live series of online services and software.
MSN Messenger is often used to refer to the .NET Messenger Service (the protocols and server that allow the system to operate) rather than any particular client.
The first product release, released July 22, 1998. It included only basic features, such as plain text messaging and a simplistic contact list.
When MSN Messenger was first released it featured support for access to America Online's AIM Network. America Online continually tried to block Microsoft from having access to their service until eventually the feature was removed, and has not re-surfaced in any later versions of the software. Now the software only allows connections to the .NET Messenger Service, requiring a Microsoft Passport Network account to connect, as well as limited contact with Yahoo Messenger.
The Real Time Streaming Protocol (RTSP) is a network control protocol designed for use in entertainment and communications systems to control streaming media servers. The protocol is used for establishing and controlling media sessions between end points. Clients of media servers issue VCR-like commands, such as play and pause, to facilitate real-time control of playback of media files from the server.
The transmission of streaming data itself is not a task of the RTSP protocol. Most RTSP servers use the Real-time Transport Protocol (RTP) in conjunction with Real-time Control Protocol (RTCP) for media stream delivery, however some vendors implement proprietary transport protocols. The RTSP server from RealNetworks, for example, also features RealNetworks' proprietary Real Data Transport (RDT).
RTSP was developed by the Multiparty Multimedia Session Control Working Group (MMUSIC WG) of the Internet Engineering Task Force (IETF) and published as RFC 2326 in 1998.
RTSP using RTP and RTCP allows for the implementation of rate adaption.
While similar in some ways to HTTP, RTSP defines control sequences useful in controlling multimedia playback. While HTTP is stateless, RTSP has state;
Siebel Internet Session Network Application Programming Interface (SISNAPI) is a proprietary (originally Siebel Systems, now Oracle) message format protocol used for communications between various Siebel application components. SISNAPI runs over HTTP and can be configured to use encryption and authentication based on Secure Sockets Layer (SSL).
SISNAPI is used for network communication between AOM and Siebel Web Server Extension (SWSE) components used by the Siebel applications. Each multithreaded process for an AOM component uses a pool of SISNAPI connections managed by the SWSE. The process multiplexes (shares) many client sessions over each connection. Each client session request opens a new connection and adds it to the pool, until the number of connections defined by the value of the parameter SessPerSisnConn have been created. Subsequent requests are then multiplexed over the existing pooled connections. SISNAPI connections persist until one of the following events occur:
For more information on this parameter, see Siebel System Administration Guide.
Multiplexing traffic over a set of SISNAPI connections helps to reduce the number of open network connections.
Telnet is a network protocol used on the Internet or local area networks to provide a bidirectional interactive text-oriented communication facility using a virtual terminal connection. User data is interspersed in-band with Telnet control information in an 8-bit byte oriented data connection over the Transmission Control Protocol (TCP).
Telnet was developed in 1969 beginning with RFC 15, extended in RFC 854, and standardized as Internet Engineering Task Force (IETF) Internet Standard STD 8, one of the first Internet standards.
Historically, Telnet provided access to a command-line interface (usually, of an operating system) on a remote host. Most network equipment and operating systems with a TCP/IP stack support a Telnet service for remote configuration (including systems based on Windows NT). Because of security issues with Telnet, its use for this purpose has waned in favor of SSH.
The term telnet may also refer to the software that implements the client part of the protocol. Telnet client applications are available for virtually all computer platforms. Telnet is also used as a verb. To telnet means to establish a connection with the Telnet protocol, either with command line
Calendaring Extensions to WebDAV, or CalDAV, is an Internet standard allowing a client to access scheduling information on a remote server. It extends WebDAV (HTTP-based protocol for data manipulation) specification and uses iCalendar format for the data. The protocol is defined by RFC 4791. It allows multiple client access to the same information thus allowing cooperative planning and information sharing. Many server and client applications support the protocol.
The CalDAV specification was first published in 2003 as an Internet Draft submitted to the Internet Engineering Task Force (IETF) by Lisa Dusseault. In March 2007, the CalDAV specification was described in the RFC 4791. CalDAV is designed for implementation by any collaborative software, client or server, that needs to maintain, access or share collections of events. It is developed as an open standard to foster interoperability between software from different implementers.
The architecture of CalDAV (partially inherited from the underlying specifications) organizes the data (events, tasks, free-busy info, notes) in directories (collections), where multiple items (resources) reside. The resources and collections can be
DICT is a dictionary network protocol created by the DICT Development Group. It is described by RFC 2229. Its goal is to surpass the Webster protocol and to allow clients to access more dictionaries during use. Dict servers and clients use TCP port 2628.
Combined, they make up the Free Internet Lexicon and Encyclopedia.
The standard dictd server made by the DICT Development Group uses a special DICT file format, although other dictd servers (such as GNU Dico) may optionally use other file formats.
Dictionaries in the standard DICT file format are made up of two files, a .index file and a .dict file (or .dict.dz if compressed). These files are not usually written manually but are compiled by a program called dictfmt. For example, the Unix command:
will compile a Unicode-compatible DICT file called mydict, with heading My Dictionary, from mydict.txt which is in Jargon File format i.e.:
Once the dictionary file has been produced, installing it in the server is normally a matter of typing something like:
A dictd server can be used from Telnet. For example, to connect to the DICT server on localhost, on a Unix system one can normally type:
and then enter the command "help" to see the
Frame Relay is a standardized wide area network technology that specifies the physical and logical link layers of digital telecommunications channels using a packet switching methodology. Originally designed for transport across Integrated Services Digital Network (ISDN) infrastructure, it may be used today in the context of many other network interfaces.
Network providers commonly implement Frame Relay for voice (VoFR) and data as an encapsulation technique, used between local area networks (LANs) over a wide area network (WAN). Each end-user gets a private line (or leased line) to a Frame Relay node. The Frame Relay network handles the transmission over a frequently-changing path transparent to all end-user extensively-used WAN protocols. It is less expensive than leased lines and that is one reason for its popularity. The extreme simplicity of configuring user equipment in a Frame Relay network offers another reason for Frame Relay's popularity.
With the advent of Ethernet over fiber optics, MPLS, VPN and dedicated broadband services such as cable modem and DSL, the end may loom for the Frame Relay protocol and encapsulation. However many rural areas remain lacking DSL and cable
Gnutella ( /nʌˈtɛlə/ with a silent g, but often /ɡnʌˈtɛlə/) (possibly by analogy with the GNU Project) is a large peer-to-peer network which, at the time of its creation, was the first decentralized peer-to-peer network of its kind, leading to other, later networks adopting the model. It celebrated a decade of existence on March 14, 2010 and has a user base in the millions for peer-to-peer file sharing.
In June 2005, gnutella's population was 1.81 million computers increasing to over three million nodes by January 2006. In late 2007, it was the most popular file sharing network on the Internet with an estimated market share of more than 40%.
The first client was developed by Justin Frankel and Tom Pepper of Nullsoft in early 2000, soon after the company's acquisition by AOL. On March 14, the program was made available for download on Nullsoft's servers. The event was prematurely announced on Slashdot, and thousands downloaded the program that day. The source code was to be released later, under the GNU General Public License (GPL).
The next day, AOL stopped the availability of the program over legal concerns and restrained Nullsoft from doing any further work on the project. This
The Financial Information eXchange (FIX) protocol is an electronic communications protocol initiated in 1992 for international real-time exchange of information related to the securities transactions and markets. With trillions of dollars traded annually on the NASDAQ alone, financial service entities are investing heavily in optimizing electronic trading and employing direct market access (DMA) to increase their speed to financial markets. Managing the delivery of trading applications and keeping latency low increasingly requires an understanding of the FIX protocol.
The FIX Protocol specification was originally authored in 1992 by Chris Morstatt and Robert "Bob" Lamoureux to enable electronic communication of equity trading data between Fidelity Investments and Salomon Brothers. FIX has become the de facto messaging standard for pre-trade and trade communication in the global equity markets, and is expanding into the post-trade space to support straight-through processing, as well as continuing to expand into foreign exchange, fixed income and derivatives markets.
FIX Protocol, Ltd. is the company established for the purpose of ownership and maintenance of the specification. It
Generic Routing Encapsulation (GRE) is a tunneling protocol developed by Cisco Systems that can encapsulate a wide variety of network layer protocols inside virtual point-to-point links over an Internet Protocol internetwork.
Generic Routing Encapsulation (GRE), defined by RFC 2784, is a simple IP packet encapsulation protocol. A GRE tunnel is used when packets need to be sent from one network to another, without being parsed or treated like IP packets by any intervening routers.
GRE tunnels are designed to be completely stateless. This means that none of the end-point tunnels keep information about the state or availability of the remote tunnel end-point. A consequence of this is that the local tunnel end-point router does not have the ability to bring the line protocol of the GRE tunnel interface down if the remote end-point is unreachable. In such a case, a network administrator can manually bring the interface down in order to remove any routes (specifically static routes) in the routing table that use that interface as the outbound interface. This allows for an alternate route with a higher metric (where a higher metric means a lower priority) or for policy-based routing (PBR)
The DeltaV distributed control system (DCS) is a control system that uses standard PC hardware for user interfaces, paired with proprietary controllers and I/O modules around a process plant or factory to control a large number of control loops using a single large system whose hardware can be distributed throughout a process plant or factory and connected with a digital data link. .
DeltaV is one of the major players in the DCS market, competing with ABB, Honeywell, General Electric, Invensys, and Yokogawa products. DeltaV replaced the widely used Provox DCS on Emerson's product line. The Pricing structure differs from most DCS systems.
The DeltaV system was created to build an automation system that could integrate with the standards developed at the time.
The DeltaV name is derived from the engineering equation for acceleration: Δv/Δt, the change in velocity over the change in time. The intent of the DeltaV system design was to accelerate the process of planning, engineering, installing, commissioning, training, operating, and maintaining an automation system.
DeltaV is used in mines, refineries, pharmaceutical plants, pulp & paper mills, and chemical plants to control a large
Internet message access protocol (IMAP) is one of the two most prevalent Internet standard protocols for e-mail retrieval, the other being the Post Office Protocol (POP). Virtually all modern e-mail clients and mail servers support both protocols as a means of transferring e-mail messages from a server.
The Internet Message Access Protocol (commonly known as IMAP) is an Application Layer Internet protocol that allows an e-mail client to access e-mail on a remote mail server. The current version, IMAP version 4 revision 1 (IMAP4rev1), is defined by RFC 3501. An IMAP server typically listens on well-known port 143. IMAP over SSL (IMAPS) is assigned well-known port number 993.
IMAP supports both on-line and off-line modes of operation. E-mail clients using IMAP generally leave messages on the server until the user explicitly deletes them. This and other characteristics of IMAP operation allow multiple clients to manage the same mailbox. Most e-mail clients support IMAP in addition to POP to retrieve messages; however, fewer e-mail services support IMAP. IMAP offers access to the mail storage. Clients may store local copies of the messages, but these are considered to be a temporary
IP multicast is a method of sending Internet Protocol (IP) datagrams to a group of interested receivers in a single transmission. It is often employed for streaming media applications on the Internet and private networks. The method is the IP-specific version of the general concept of multicast networking. It uses specially reserved multicast address blocks in IPv4 and IPv6. In IPv6, IP multicast addressing replaces broadcast addressing as implemented in IPv4.
IP multicast is described in RFC 1112. IP multicast was first standardized in 1986. Its specifications have been augmented in RFC 4604 to include group management and in RFC 5771 to include administratively scoped addresses.
IP multicast is a technique for one-to-many and many-to-many real-time communication over an IP infrastructure in a network. It scales to a larger receiver population by requiring neither prior knowledge of a receiver's identity nor prior knowledge of the number of receivers. Multicast uses network infrastructure efficiently by requiring the source to send a packet only once, even if it needs to be delivered to a large number of receivers. The nodes in the network (typically network switches and routers)
Internetwork Packet Exchange (IPX) is the OSI-model Network layer protocol in the IPX/SPX protocol stack.
The IPX/SPXM protocol stack is supported by Novell's NetWare network operating system. Because of Netware's popularity through the late 1980s into the mid 1990s, IPX became a popular internetworking protocol. Novell derived IPX from Xerox Network Systems' IDP.
IPX did not scale enough for large networks such as the internet and as such, IPX usage decreased as the boom of the Internet made TCP/IP nearly universal. Computers and networks can run multiple network protocols, so almost all IPX sites will be running TCP/IP as well to allow for Internet connectivity. It has also been possible to run Novell products without IPX for some time, as they have supported both IPX and TCP/IP since NetWare reached version 5 in late 1998.
The IPX network address is conceptually identical to the network part of the IP address (the parts with netmask bits set to 1); the node address then has the same meaning as the bits of IP address with netmask bits set to 0. As the node address is usually identical to the MAC address of the network adapter, the Address Resolution Protocol is not needed.
LocalTalk is a particular implementation of the physical layer of the AppleTalk networking system from Apple Computer. LocalTalk specifies a system of shielded twisted pair cabling, plugged into self-terminating transceivers, running at a rate of 230.4 kbit/s. CSMA/CA was implemented as a random multiple access method.
Networking was envisioned in the Macintosh during planning, so the Mac was given expensive RS-422 capable serial ports. The ports were driven by the Zilog SCC which could serve as either a standard UART or handle the much more complicated HDLC protocol which was a packet oriented protocol which incorporated addressing, bit-stuffing, and packet checksumming in hardware. Coupled together with the RS422 electrical connections, this provided a reasonably high-speed data connection.
The 230.4 kbit/s bit rate is the highest in the series of standard serial bit rates (110, 150, 300, 600, 1200, 2400, 4800, 9600, 14400, 19200, 28800, 38400, 57600, 115200, 230400) derived from the 3.6864 MHz clock after the customary divide-by-16. This clock frequency, 3.6864 MHz, was chosen (in part) to support the common asynchronous baud rates up to 38.4 kbit/s using the SCC's internal
NetBIOS ( /ˈnɛtbaɪ.oʊs/) is an acronym for Network Basic Input/Output System. It provides services related to the session layer of the OSI model allowing applications on separate computers to communicate over a local area network. As strictly an API, NetBIOS is not a networking protocol. Older operating systems ran NetBIOS over IEEE 802.2 and IPX/SPX using the NetBIOS Frames (NBF) and NetBIOS over IPX/SPX (NBX) protocols, respectively. In modern networks, NetBIOS normally runs over TCP/IP via the NetBIOS over TCP/IP (NBT) protocol. This results in each computer in the network having both an IP address and a NetBIOS name corresponding to a (possibly different) host name.
NetBIOS was developed in 1983 by Sytek Inc. as an API for software communication over IBM PC Network LAN technology. On PC-Network, as an API alone, NetBIOS relied on proprietary Sytek networking protocols for communication over the wire. Because PC Network only supported up to 80 devices in its most accommodating mode (baseband), NetBIOS was itself designed with limited nodes in mind.
In 1985, IBM went forward with the token ring network scheme and a NetBIOS emulator was produced to allow NetBIOS-aware applications
rlogin is a software utility for Unix-like computer operating systems that allows users to log in on another host via a network, communicating via TCP port 513.
It was first distributed as part of the 4.2BSD release.
rlogin is also the name of the application layer protocol used by the software, part of the TCP/IP protocol suite. Authenticated users can act as if they were physically present at the computer. RFC 1282, in which it was defined, states that: "The rlogin facility provides a remote-echoed, locally flow-controlled virtual terminal with proper flushing of output." rlogin communicates with a daemon, rlogind, on the remote host. rlogin is similar to the Telnet command, but has the disadvantage of not being as customizable and being able to connect only to Unix hosts.
rlogin is most commonly deployed on corporate or academic networks, where user account information is shared between all the Unix machines on the network (often using NIS). These deployments essentially trust ALL other machines (and the network infrastructure itself) and the rlogin protocol relies on this trust. rlogind allows logins without password (where rlogind trusts a remote rlogin client) if the remote
The name Atom applies to a pair of related standards. The Atom Syndication Format is an XML language used for web feeds, while the Atom Publishing Protocol (AtomPub or APP) is a simple HTTP-based protocol for creating and updating web resources.
Web feeds allow software programs to check for updates published on a website. To provide a web feed, a site owner may use specialized software (such as a content management system) that publishes a list (or "feed") of recent articles or content in a standardized, machine-readable format. The feed can then be downloaded by programs that use it, like websites that syndicate content from the feed, or by feed reader programs that allow Internet users to subscribe to feeds and view their content.
A feed contains entries, which may be headlines, full-text articles, excerpts, summaries, and/or links to content on a website, along with various metadata.
The Atom format was developed as an alternative to RSS. Ben Trott, an advocate of the new format that became Atom, believed that RSS had limitations and flaws—such as lack of on-going innovation and its necessity to remain backward compatible— and that there were advantages to a fresh
OpenURL is a standardized format of Uniform Resource Locator (URL) intended to enable Internet users to more easily find a copy of a resource that they are allowed to access. Although OpenURL can be used with any kind of resource on the Internet, it is most heavily used by libraries to help connect patrons to subscription content.
The OpenURL standard is designed to enable linking from information resources such as abstracting and indexing databases (sources) to library services (targets), such as academic journals, whether online or in printed or other formats. The linking is mediated by "link resolvers", or "link-servers", which parse the elements of an OpenURL and provide links to appropriate targets available through a library by the use of an OpenURL knowledge base.
The source that generates an OpenURL is typically a bibliographic citation or bibliographic record in a database that indexes the information resources often found in libraries, such as articles, books, patents, etc. Examples of such databases include Ovid, Web of Science, SciFinder, Modern Languages Association Bibliography and Google Scholar.
A target is a resource or service that helps satisfy a user's
Universal Description, Discovery and Integration (UDDI, pronounced Yu-diː) is a platform-independent, Extensible Markup Language (XML)-based registry by which businesses worldwide can list themselves on the Internet, and a mechanism to register and locate web service applications. UDDI is an open industry initiative, sponsored by the Organization for the Advancement of Structured Information Standards (OASIS), for enabling businesses to publish service listings and discover each other, and to define how the services or software applications interact over the Internet.
UDDI was originally proposed as a core Web service standard. It is designed to be interrogated by SOAP messages and to provide access to Web Services Description Language (WSDL) documents describing the protocol bindings and message formats required to interact with the web services listed in its directory.
UDDI was written in August 2000, at a time when the authors had a vision of a world in which consumers of web services would be linked up with providers through a public or private dynamic brokerage system. In this vision, anyone needing a service, such as credit card authentication, would go to their service
The Web Services Description Language is an XML-based language that is used for describing the functionality offered by a Web service. A WSDL description of a web service (also referred to as a WSDL file) provides a machine-readable description of how the service can be called, what parameters it expects, and what data structures it returns. It thus serves a roughly similar purpose as a method signature in a programming language.
The current version of WSDL is WSDL 2.0. The meaning of the acronym has changed from version 1.1 where the D stood for Definition.
The WSDL describes services as collections of network endpoints, or ports. The WSDL specification provides an XML format for documents for this purpose. The abstract definitions of ports and messages are separated from their concrete use or instance, allowing the reuse of these definitions. A port is defined by associating a network address with a reusable binding, and a collection of ports defines a service. Messages are abstract descriptions of the data being exchanged, and port types are abstract collections of supported operations. The concrete protocol and data format specifications for a particular port type constitutes a
AppleTalk is a proprietary suite of networking protocols developed by Apple Inc. for their Mac computers. AppleTalk included a number of features that allowed local area networks to be connected with no prior setup or the need for a centralized router or server of any sort. Connecting together AppleTalk equipped systems would automatically assign addresses, update the distributed namespace, and configure any required inter-networking routing. It was a plug-n-play system.
AppleTalk was released for the original Macintosh in 1985, and was the primary protocol used by Apple devices through the 1980s and 90s. Versions were also released for the IBM PC and compatibles, and the Apple IIGS. AppleTalk support was also available in most networked printers (especially laser printers), some file servers and a number of routers.
The rise of TCP/IP during the 1990s led to a re-implementation of most of these types of support on that protocol, and AppleTalk became unsupported as of the release of Mac OS X v10.6 in 2009. Many of AppleTalk's more advanced auto-configuration features have since been introduced in Bonjour.
After the release of the Apple Lisa computer in January 1983, Apple invested
ARCNET (also CamelCased as ARCnet, an acronym from Attached Resource Computer NETwork) is a local area network (LAN) protocol, similar in purpose to Ethernet or Token Ring. ARCNET was the first widely available networking system for microcomputers and became popular in the 1980s for office automation tasks. It has since gained a following in the embedded systems market, where certain features of the protocol are especially useful.
ARCNET was developed by principal development engineer John Murphy at Datapoint Corporation in 1976 under Victor Poor, and announced in 1977. It was originally developed to connect groups of their Datapoint 2200 terminals to talk to a shared 8" floppy disk system. As microcomputers took over from the Datapoint, ARCNET was re-purposed as LAN. It was the first loosely-coupled LAN-based clustering solution, making no assumptions about the type of computers that would be connected. This was in contrast to contemporary larger and more expensive computer systems such as DECnet or SNA, where a homogeneous group of similar or proprietary computers were connected as a cluster.
The token-passing bus protocol of that I/O device-sharing network was subsequently
SPARQL (pronounced "sparkle", a recursive acronym for SPARQL Protocol and RDF Query Language) is an RDF query language, that is, a query language for databases, able to retrieve and manipulate data stored in Resource Description Framework format. It was made a standard by the RDF Data Access Working Group (DAWG) of the World Wide Web Consortium, and considered as one of the key technologies of semantic web. On 15 January 2008, SPARQL 1.0 became an official W3C Recommendation .
SPARQL allows for a query to consist of triple patterns, conjunctions, disjunctions, and optional patterns.
Implementations for multiple programming languages exist. "SPARQL will make a huge difference" according to Sir Tim Berners-Lee in a May 2006 interview.
There exist tools that allow one to connect and semi-automatically construct a SPARQL query for a SPARQL endpoint, for example ViziQuer. In addition, there exist tools that translate SPARQL queries to other query languages, for example to SQL and to XQuery.
SPARQL allows users to write unambiguous queries. For example, the following query returns names and emails of every person in the dataset:
This query can be distributed to multiple SPARQL endpoints
Simple Network Management Protocol (SNMP) is an "Internet-standard protocol for managing devices on IP networks." Devices that typically support SNMP include routers, switches, servers, workstations, printers, modem racks, and more." It is used mostly in network management systems to monitor network-attached devices for conditions that warrant administrative attention. SNMP is a component of the Internet Protocol Suite as defined by the Internet Engineering Task Force (IETF). It consists of a set of standards for network management, including an application layer protocol, a database schema, and a set of data objects.
SNMP exposes management data in the form of variables on the managed systems, which describe the system configuration. These variables can then be queried (and sometimes set) by managing applications.
In typical SNMP uses, one or more administrative computers, called managers, have the task of monitoring or managing a group of hosts or devices on a computer network. Each managed system executes, at all times, a software component called an agent which reports information via SNMP to the manager.
Essentially, SNMP agents expose management data on the managed systems as
Connectionless-mode Network Service (CLNS) or simply Connectionless Network Service is an OSI Network Layer datagram service that does not require a circuit to be established before data is transmitted and routes messages to their destinations independently of any other messages. As such it is a "best-effort" rather than a "reliable" delivery service. CLNS is not an Internet service, but provides capabilities in an OSI network environment similar to those provided by the Internet Protocol (IP) and the User Datagram Protocol (UDP).
In an OSI protocol deployment, CLNS is the service provided by the Connectionless-mode Network Protocol (CLNP). CLNP is widely used in many telecommunications networks around the world because IS-IS (an OSI layer 3 protocol) is mandated by the ITU-T as the protocol for management of Synchronous Digital Hierarchy (SDH) elements. From August 1990 to April 1995 the NSFNET backbone supported CLNP in addition to TCP/IP. However, CLNP usage remained low compared to TCP/IP.
CLNS is used by ISO Transport Protocol Class 4 (TP4), one of the five transport layer protocols in the OSI suite. TP4 offers error recovery, performs segmentation and reassembly, and supplies
The Network News Transfer Protocol (NNTP) is an application protocol used for transporting Usenet news articles (netnews) between news servers and for reading and posting articles by end user client applications. Brian Kantor of the University of California, San Diego and Phil Lapsley of the University of California, Berkeley authored RFC 977, the specification for the Network News Transfer Protocol, in March 1986. Other contributors included Stan O. Barber from the Baylor College of Medicine and Erik Fair of Apple Computer.
Usenet was originally designed based on the UUCP network, with most article transfers taking place over direct point-to-point telephone links between news servers, which were powerful time-sharing systems. Readers and posters logged into these computers reading the articles directly from the local disk.
As local area networks and Internet participation proliferated, it became desirable to allow newsreaders to be run on personal computers connected to local networks. Because distributed file systems were not yet widely available, a new protocol was developed based on the client-server model. It resembled the Simple Mail Transfer Protocol (SMTP), but was tailored
In networking, the Point-to-Point Protocol (PPP) is a data link protocol commonly used in establishing a direct connection between two networking nodes. It can provide connection authentication, transmission encryption (using ECP, RFC 1968), and compression.
PPP is used over many types of physical networks including serial cable, phone line, trunk line, cellular telephone, specialized radio links, and fiber optic links such as SONET. PPP is also used over Internet access connections (now marketed as "broadband"). Internet service providers (ISPs) have used PPP for customer dial-up access to the Internet, since IP packets cannot be transmitted over a modem line on their own, without some data link protocol. Two encapsulated forms of PPP, Point-to-Point Protocol over Ethernet (PPPoE) and Point-to-Point Protocol over ATM (PPPoA), are used most commonly by Internet Service Providers (ISPs) to establish a Digital Subscriber Line (DSL) Internet service connection with customers.
PPP is commonly used as a data link layer protocol for connection over synchronous and asynchronous circuits, where it has largely superseded the older Serial Line Internet Protocol (SLIP) and telephone company
In computer networking, Server Message Block (SMB), also known as Common Internet File System (CIFS, /ˈsɪfs/) operates as an application-layer network protocol mainly used for providing shared access to files, printers, serial ports, and miscellaneous communications between nodes on a network. It also provides an authenticated inter-process communication mechanism. Most usage of SMB involves computers running Microsoft Windows, where it was known as "Microsoft Windows Network" before the subsequent introduction of Active Directory. Corresponding Windows services are the "Server Service" (for the server component) and "Workstation Service" (for the client component).
The Server Message Block protocol can run atop the Session (and lower) network layers in several ways:
Barry Feigenbaum originally designed SMB at IBM with the aim of turning DOS "Interrupt 33" (21h) local file access into a networked file system. Microsoft has made considerable modifications to the most commonly used version. Microsoft merged the SMB protocol with the LAN Manager product which it had started developing for OS/2 with 3Com c. 1990, and continued to add features to the protocol in Windows for Workgroups
Telephone User Part (TUP) provides conventional PSTN telephony services across the SS7 network. TUP was the first layer 4 protocol defined by the standards bodies and as such did not provision for ISDN services. It has now largely been replaced by ISUP. However, it can still be found in operational use in some parts of the world (e.g. China).
TUP is defined in ITU-T Recommendations Q.721-725. These define the international telephone call control signalling functions for use over SS7.
Various national variants of TUP have evolved, some of which provide varying degrees of support for ISDN. E.g. French SSUTR2 and Chinese TUP (Specification GF001-9001).
Content Management Interoperability Services (CMIS) is an open standard that defines an abstraction layer for controlling diverse document management systems and repositories using web protocols. CMIS defines a domain model plus Web Services and Restful AtomPub (RFC5023) bindings that can be used by applications. OASIS, a web standards consortium, approved CMIS as an OASIS Specification on May 1, 2010. CMIS 1.1 began its public review draft state (as of Sept 2012) at OASIS.
CMIS provides a common data model covering typed files and folders with generic properties that can be set or read. There is a set of services for adding and retrieving documents ('objects'). There may be an access control system, a checkout and version control facility, and the ability to define generic relations. Two protocol bindings are defined, one using WSDL and SOAP and another using Representational State Transfer (REST), using the AtomPub convention. The model is based on common architectures of document management systems.
Although initiated by AIIM, CMIS is now administered by the OASIS standards body. Participants in the process include Adobe Systems Incorporated, Alfresco, EMC, eXo, FatWire, HP,
Reservation ALOHA, or R-ALOHA, is a channel access method for wireless (or other shared channel) transmission that allows uncoordinated users to share a common transmission resource. Reservation ALOHA (and its parent scheme, Slotted ALOHA) is a schema or rule set for the division of transmission resources over fixed time increments, also known as slots. If followed by all devices, this scheme allows the channel's users to cooperatively utilize a shared transmission resource—in this case, it is the allocation of transmission time.
Reservation ALOHA is an effort to improve the efficiency of Slotted ALOHA. The improvements with Reservation ALOHA are markedly shorter delays and ability to efficiently support higher levels of utilization. As a contrast of efficiency, simulations have shown that Reservation ALOHA exhibits less delay at 80% utilization than Slotted ALOHA at 20–36% utilization.
The chief difference between Slotted and Reservation ALOHA is that with Slotted ALOHA, any slot is available for utilization without regards to prior usage. Under Reservation ALOHA's contention-based reservation schema, the slot is temporarily considered "owned" by the station that successfully used
SOAP, originally defined as Simple Object Access Protocol, is a protocol specification for exchanging structured information in the implementation of Web Services in computer networks. It relies on Extensible Markup Language (XML) for its message format, and usually relies on other Application Layer protocols, most notably Hypertext Transfer Protocol (HTTP) and Simple Mail Transfer Protocol (SMTP), for message negotiation and transmission.
SOAP can form the foundation layer of a web services protocol stack, providing a basic messaging framework upon which web services can be built. This XML based protocol consists of three parts: an envelope, which defines what is in the message and how to process it, a set of encoding rules for expressing instances of application-defined datatypes, and a convention for representing procedure calls and responses. SOAP has three major characteristics: Extensibility (security and WS-routing are among the extensions under development), Neutrality (SOAP can be used over any transport protocol such as HTTP, SMTP, TCP, or JMS) and Independence (SOAP allows for any programming model).
As an example of how SOAP procedures can be used, a SOAP message could
The Yahoo! Messenger Protocol is the underlying network protocol used by the Yahoo! Messenger instant messaging client, for Yahoo!. Yahoo! Instant Messager supports many features beyond just messaging, including off-line messaging, file transfer, chat, conferencing, voice chat, webcam and avatar.
The purpose of the YMSG protocol is to provide a language and series of conventions for software communicating with Yahoo!'s Instant Messaging service. In essence YMSG performs the same role for IM as HTTP does for the World Wide Web. Unlike HTTP, however, YMSG is a proprietary standard, aligned only with a single messaging service provider (namely, Yahoo!). Rival messaging services have their own protocols, some based on open standards, others proprietary, each effectively fulfilling the same role with different mechanics.
One of the fundamental tenets of instant messaging is the notion that users can see when someone is connected to the network known in the jargon as 'presence'. Yahoo!'s protocol uses the mechanics of a standard internet connection to achieve presence, the same connection it uses to send and receive data. In order for each user to remain 'visible' to other users on
A comma-separated values (CSV) file stores tabular data (numbers and text) in plain-text form. Plain text means that the file is a sequence of characters, with no data that has to be interpreted instead, as binary numbers. A CSV file consists of any number of records, separated by line breaks of some kind; each record consists of fields, separated by some other character or string, most commonly a literal comma or tab. Usually, all records have an identical sequence of fields.
CSV is a common, relatively simple file format that is widely supported by consumer, business, and scientific applications. Among its most common uses is moving tabular data between programs that natively operate on incompatible (often proprietary and/or undocumented) formats. This works because so many programs support some variation of CSV at least as an alternative import/export format.
For example, a user may need to transfer information from a database program that stores data in a proprietary format, to a spreadsheet that uses a completely different format. The database program most likely can export its data as "CSV"; the exported CSV file can then be imported by the spreadsheet program.
"CSV" is not a
The Domain Name System (DNS) is a hierarchical distributed naming system for computers, services, or any resource connected to the Internet or a private network. It associates various information with domain names assigned to each of the participating entities. A Domain Name Service resolves queries for these names into IP addresses for the purpose of locating computer services and devices worldwide. By providing a worldwide, distributed keyword-based redirection service, the Domain Name System is an essential component of the functionality of the Internet.
An often-used analogy to explain the Domain Name System is that it serves as the phone book for the Internet by translating human-friendly computer hostnames into IP addresses. For example, the domain name www.example.com translates to the addresses 18.104.22.168 (IPv4) and 2620:0:2d0:200::10 (IPv6). Unlike a phone book, however, DNS can be quickly updated and these updates distributed, allowing a service's location on the network to change without affecting the end users, who continue to use the same hostname. Users take advantage of this when they recite meaningful Uniform Resource Locators (URLs) and e-mail addresses without
FastCGI is a protocol for interfacing interactive programs with a web server. FastCGI is a variation on the earlier Common Gateway Interface (CGI); FastCGI's main aim is to reduce the overhead associated with interfacing the web server and CGI programs, allowing a server to handle more web page requests at once.
CGI is a protocol for interfacing external applications to web servers. CGI applications run in separate processes, which are created at the start of each request and torn down at the end. This "one new process per request" model makes CGI programs very simple to implement, but limits efficiency and scalability. At high loads, the operating system process creation and destruction overhead becomes significant. In addition, the CGI process model limits resource reuse techniques (such as reusing database connections, in-memory caching, etc.).
To address the scalability shortcomings of CGI, Open Market developed FastCGI and first introduced it in their webserver product in the mid-1990s. Open Market originally developed FastCGI in part as a competitive response to Netscape's proprietary, in-process API (NSAPI) for developing Web applications.
Although initially developed by
In Integrated Services Digital Network (ISDN) telecommunications, Link Access Procedures, D channel is part of the network's communications protocol which ensures that messages are error free and executed in the right sequence.
LAPD is the second layer protocol on the ISDN protocol stack in the D channel (the ISDN channel in which the control and signalling information is carried).
LAPD standards are specified in ITU-T Q.920 and Q.921. Its development was heavily based on High-Level Data Link Control.
Open Shortest Path First (OSPF) is an link-state routing protocol for Internet Protocol (IP) networks. It uses a link state routing algorithm and falls into the group of interior routing protocols, operating within a single autonomous system (AS). It is defined as OSPF Version 2 in RFC 2328 (1998) for IPv4. The updates for IPv6 are specified as OSPF Version 3 in RFC 5340 (2008).
OSPF is perhaps the most widely used interior gateway protocol (IGP) in large enterprise networks. IS-IS, another link-state dynamic routing protocol, is more common in large service provider networks. The most widely used exterior gateway protocol is the Border Gateway Protocol (BGP), the principal routing protocol between autonomous systems on the Internet.
OSPF is an interior gateway protocol that routes Internet Protocol (IP) packets solely within a single routing domain (autonomous system). It gathers link state information from available routers and constructs a topology map of the network. The topology determines the routing table presented to the Internet Layer which makes routing decisions based solely on the destination IP address found in IP packets. OSPF was designed to support variable-length
Serial Storage Architecture (SSA) is a serial transport protocol used to attach disk drives to servers. It was invented by Ian Judd of IBM in 1990. IBM produced a number of successful products based upon this standard before it was overtaken by the more widely adopted Fibre Channel protocol.
SSA was promoted as an open standard by the SSA Industry Association, unlike its predecessor the first generation Serial Disk Subsystem. A number of vendors including IBM, Pathlight Technology and Viacom produced products based on SSA. It was also adopted as an ANSI X3T10.1 standard. SSA devices are logically SCSI devices and conform to all of the SCSI command protocols.
SSA provides data protection for critical applications by helping to ensure that a single cable failure will not prevent access to data. All the components in a typical SSA subsystem are connected by bi-directional cabling. Data sent from the adaptor can travel in either direction around the loop to its destination. SSA detects interruptions in the loop and automatically reconfigures the system to help maintain connection while a link is restored.
Up to 192 hot swappable hard disk drives can be supported per system. Drives can
The Spanning Tree Protocol (STP) is a network protocol that ensures a loop-free topology for any bridged Ethernet local area network. The basic function of STP is to prevent bridge loops and the broadcast radiation that results from them. Spanning tree also allows a network design to include spare (redundant) links to provide automatic backup paths if an active link fails, without the danger of bridge loops, or the need for manual enabling/disabling of these backup links.
Spanning Tree Protocol (STP) is standardized as IEEE 802.1D. As the name suggests, it creates a spanning tree within a mesh network of connected layer-2 bridges (typically Ethernet switches), and disables those links that are not part of the spanning tree, leaving a single active path between any two network nodes.
STP is based on an algorithm invented by Radia Perlman while working for Digital Equipment Corporation.
The collection of bridges in a local area network (LAN) can be depicted as a graph whose nodes are bridges and LAN segments (or cables), and whose edges are the interfaces connecting the bridges to the segments. To break loops in the LAN while maintaining access to all LAN segments, the bridges
Enhanced Interior Gateway Routing Protocol - (EIGRP) is a Cisco proprietary routing protocol loosely based on their original IGRP. EIGRP is an advanced distance-vector routing protocol, with optimizations to minimize both the routing instability incurred after topology changes, as well as the use of bandwidth and processing power in the router. Routers that support EIGRP will automatically redistribute route information to IGRP neighbors by converting the 32 bit EIGRP metric to the 24 bit IGRP metric. Most of the routing optimizations are based on the Diffusing Update Algorithm (DUAL) work from SRI, which guarantees loop-free operation and provides a mechanism for fast convergence.
EIGRP stores data in three tables:
Unlike most other distance vector protocols, EIGRP does not rely on periodic route dumps in order to maintain its topology table. Routing information is exchanged only upon the establishment of new neighbor adjacencies, after which only changes are sent. Also, it uses route tagging.
EIGRP associates six (6) different vector metrics with each route and considers only four (4) of the vector metrics in computing the Composite
Xerox Network Services (XNS) is a protocol suite developed by Xerox within the Xerox Network Systems Architecture. It provided general purpose network communications, internetwork routing and packet delivery, including higher level functions such as a reliable stream, and remote procedure calls. XNS predated and influenced the development of the Open Systems Interconnect (OSI) networking model.
XNS was developed at Xerox PARC in the early 1980s, based heavily on the earlier (and extremely influential) PARC Universal Packet (PUP) protocol suite done there in the late 1970s; some of the protocols in the XNS suite were lightly modified versions of the ones in the PUP suite. XNS was intended to be a commercial descendant of the research/development oriented PUP. The protocol suite specifications were placed in the public domain.
Being in the public domain, XNS became a canonical local area networking protocol in the 1980s, copied to various degrees by practically all networking systems in use into the 1990s. It had little impact on TCP/IP, however. During the 1980s XNS was used by 3Com and, with modifications, by a number of other commercial systems which became more common than XNS
Extensible Markup Language (XML) is a markup language that defines a set of rules for encoding documents in a format that is both human-readable and machine-readable. It is defined in the XML 1.0 Specification produced by the W3C, and several other related specifications, all gratis open standards.
The design goals of XML emphasize simplicity, generality, and usability over the Internet. It is a textual data format with strong support via Unicode for the languages of the world. Although the design of XML focuses on documents, it is widely used for the representation of arbitrary data structures, for example in web services.
Many application programming interfaces (APIs) have been developed for software developers to use to process XML data, and several schema systems exist to aid in the definition of XML-based languages.
As of 2009, hundreds of XML-based languages have been developed, including RSS, Atom, SOAP, and XHTML. XML-based formats have become the default for many office-productivity tools, including Microsoft Office (Office Open XML), OpenOffice.org and LibreOffice (OpenDocument), and Apple's iWork. XML has also been employed as the base language for communication
The Sitemaps protocol allows a webmaster to inform search engines about URLs on a website that are available for crawling. A Sitemap is an XML file that lists the URLs for a site. It allows webmasters to include additional information about each URL: when it was last updated, how often it changes, and how important it is in relation to other URLs in the site. This allows search engines to crawl the site more intelligently. Sitemaps are a URL inclusion protocol and complement robots.txt, a URL exclusion protocol.
Sitemaps are particularly beneficial on websites where:
Sitemaps supplement and do not replace the existing crawl-based mechanisms that search engines already use to discover URLs. Using this protocol does not guarantee that web pages will be included in search indexes, nor does it influence the way that pages are ranked in search results.
Google first introduced Sitemaps 0.84 in June 2005 so web developers could publish lists of links from across their sites. Google, MSN and Yahoo announced joint support for the Sitemaps protocol in November 2006. The schema version was changed to "Sitemap 0.90", but no other changes were made.
In April 2007, Ask.com and IBM announced
Internet Protocol television (IPTV) is a system through which television services are delivered using the Internet protocol suite over a packet-switched network such as the Internet, instead of being delivered through traditional terrestrial, satellite signal, and cable television formats.
IPTV services may be classified into three main groups:
IPTV is distinguished from Internet television by its on-going standardization process (e.g., European Telecommunications Standards Institute) and preferential deployment scenarios in subscriber-based telecommunications networks with high-speed access channels into end-user premises via set-top boxes or other customer-premises equipment.
Historically, many different definitions of IPTV have appeared, including elementary streams over IP networks, transport streams over IP networks and a number of proprietary systems.
One official definition approved by the International Telecommunication Union focus group on IPTV (ITU-T FG IPTV) is:
"IPTV is defined as multimedia services such as television/video/audio/text/graphics/data delivered over IP based networks managed to provide the required level of quality of service and experience, security,
The Link Layer Discovery Protocol (LLDP) is a vendor-neutral Link Layer protocol in the Internet Protocol Suite used by network devices for advertising their identity, capabilities, and neighbors on a IEEE 802 local area network, principally wired Ethernet. The protocol is formally referred to by the IEEE as Station and Media Access Control Connectivity Discovery specified in standards document IEEE 802.1AB.
LLDP performs functions similar to several proprietary protocols, such as the Cisco Discovery Protocol, Extreme Discovery Protocol, Nortel Discovery Protocol (also known as SONMP), and Microsoft's Link Layer Topology Discovery (LLTD).
LLDP information is sent by devices from each of their interfaces at a fixed interval, in the form of an Ethernet frame. Each frame contains one LLDP Data Unit (LLDPDU). Each LLDPDU is a sequence of type-length-value (TLV) structures.
The Ethernet frame used in LLDP has its destination MAC address typically set to a special multicast address that 802.1D-compliant bridges do not forward Other multicast and unicast destination addresses are permitted. The EtherType field is set to 0x88cc.
Each LLDP frame starts with the following mandatory TLVs:
The Media Gateway Control Protocol is an architecture for controlling media gateways on Internet Protocol (IP) networks and the public switched telephone network (PSTN).
The Media Gateway Control Protocol architecture and its methodologies and programming interfaces are described in RFC 2805.
Two implementations of the Media Gateway Control Protocol are in common use. The names of both are abbreviations of the protocol group:
Although similar in architecture, MGCP and Megaco are distinctly different protocols and are not interoperable.
The Secure Real-time Transport Protocol (or SRTP) defines a profile of RTP (Real-time Transport Protocol), intended to provide encryption, message authentication and integrity, and replay protection to the RTP data in both unicast and multicast applications. It was developed by a small team of IP protocol and cryptographic experts from Cisco and Ericsson including David Oran, David McGrew, Mark Baugher, Mats Naslund, Elisabetta Carrara, James Black, Karl Norman, and Rolf Blom. It was first published by the IETF in March 2004 as RFC 3711.
Since RTP is closely related to RTCP (Real Time Control Protocol) which can be used to control the RTP session, SRTP also has a sister protocol, called Secure RTCP (or SRTCP); SRTCP provides the same security-related features to RTCP, as the ones provided by SRTP to RTP.
Utilization of SRTP or SRTCP is optional to the utilization of RTP or RTCP; but even if SRTP/SRTCP are used, all provided features (such as encryption and authentication) are optional and can be separately enabled or disabled. The only exception is the message authentication feature which is indispensably required when using SRTCP.
For encryption and decryption of the data flow
The Serial Line Internet Protocol (SLIP) is an encapsulation of the Internet Protocol designed to work over serial ports and modem connections. It is documented in RFC 1055. On personal computers, SLIP has been largely replaced by the Point-to-Point Protocol (PPP), which is better engineered, has more features and does not require its IP address configuration to be set before it is established. On microcontrollers, however, SLIP is still the preferred way of encapsulating IP packets due to its very small overhead.
SLIP modifies a standard TCP/IP datagram by appending a special "SLIP END" character to it, which distinguishes datagram boundaries in the byte stream. SLIP requires a serial port configuration of 8 data bits, no parity, and either EIA hardware flow control, or CLOCAL mode (3-wire null-modem) UART operation settings.
SLIP does not provide error detection, being reliant on upper layer protocols for this. Therefore SLIP on its own is not satisfactory over an error-prone dial-up connection. It is however still useful for testing operating systems' response capabilities under load (by looking at flood-ping statistics).
SLIP is also currently used in the BlueCore Serial
In telecommunications, RS-232 is the traditional name for a series of standards for serial binary single-ended data and control signals connecting between a DTE (Data Terminal Equipment) and a DCE (Data Circuit-terminating Equipment). It is commonly used in computer serial ports. The standard defines the electrical characteristics and timing of signals, the meaning of signals, and the physical size and pinout of connectors. The current version of the standard is TIA-232-F Interface Between Data Terminal Equipment and Data Circuit-Terminating Equipment Employing Serial Binary Data Interchange, issued in 1997.
An RS-232 port was once a standard feature of a personal computer for connections to modems, printers, mice, data storage, uninterruptible power supplies, and other peripheral devices. However, the low transmission speed, large voltage swing, and large standard connectors motivated development of the universal serial bus, which has displaced RS-232 from most of its peripheral interface roles. Many modern personal computers have no RS-232 ports and must use an external converter to connect to older peripherals. Some RS-232 devices are still found, especially in industrial
Multiprotocol Label Switching (MPLS) is a mechanism in high-performance telecommunications networks that directs data from one network node to the next based on short path labels rather than long network addresses, avoiding complex lookups in a routing table. The labels identify virtual links (paths) between distant nodes rather than endpoints. MPLS can encapsulate packets of various network protocols. MPLS supports a range of access technologies, including T1/E1, ATM, Frame Relay, and DSL.
MPLS is a highly scalable, protocol agnostic, data-carrying mechanism. In an MPLS network, data packets are assigned labels. Packet-forwarding decisions are made solely on the contents of this label, without the need to examine the packet itself. This allows one to create end-to-end circuits across any type of transport medium, using any protocol. The primary benefit is to eliminate dependence on a particular OSI model data link layer technology, such as Asynchronous Transfer Mode (ATM), Frame Relay, Synchronous Optical Networking (SONET) or Ethernet, and eliminate the need for multiple layer-2 networks to satisfy different types of traffic. MPLS belongs to the family of packet-switched
In computing, the SSH File Transfer Protocol (also Secret File Transfer Protocol, Secure FTP, or SFTP) is a network protocol that provides file access, file transfer, and file management functionalities over any reliable data stream. It was designed by the Internet Engineering Task Force (IETF) as an extension of the Secure Shell protocol (SSH) version 2.0 to provide secure file transfer capability, but is also intended to be usable with other protocols. The IETF of the Internet Draft states that even though this protocol is described in the context of the SSH-2 protocol, it could be used in a number of different applications, such as secure file transfer over Transport Layer Security (TLS) and transfer of management information in VPN applications.
This protocol assumes that it is run over a secure channel, such as SSH, that the server has already authenticated the client, and that the identity of the client user is available to the protocol.
Compared to the earlier SCP protocol, which allows only file transfers, the SFTP protocol allows for a range of operations on remote files – it is more like a remote file system protocol. An SFTP client's extra capabilities compared to an SCP
The Ethernet physical layer is the physical layer component of the Ethernet family of computer network standards.
The Ethernet physical layer evolved over a considerable time span and encompasses quite a few physical media interfaces and several magnitudes of speed. The speed ranges from 1 Mbit/s to 100 Gbit/s while the physical medium can range from bulky coaxial cable to twisted pair to optical fiber. In general, network protocol stack software will work similarly on all physical layers.
10 Gigabit Ethernet is becoming more popular in both enterprise and carrier networks, with 40 Gbit/s and 100 Gbit/s Ethernet ratified. Higher speeds are under development. Robert Metcalfe, one of the co-inventors of ethernet, now believes commercial applications using terabit Ethernet may occur by 2015 though he says existing Ethernet standards may have to be overthrown to reach terabit Ethernet.
Many Ethernet adapters and switch ports support multiple speeds, using autonegotiation to set the speed and duplex for the best values supported by both connected devices. If auto-negotiation fails, a multiple speed device will sense the speed used by its partner, but will assume half-duplex. A 10/100
The Internet Group Management Protocol (IGMP) is a communications protocol used by hosts and adjacent routers on IP networks to establish multicast group memberships.
IGMP is an integral part of the IP multicast specification. IGMP can be used for online streaming video and gaming, and allows more efficient use of resources when supporting these types of applications.
IGMP is used on IPv4 networks. Multicast management on IPv6 networks is handled by Multicast Listener Discovery (MLD) which uses ICMPv6 messaging in contrast to IGMP's bare IP encapsulation.
A network designed to deliver a multicast service using IGMP might use this basic architecture:
IGMP operates between the client computer and a local multicast router. Switches featuring IGMP snooping derive useful information by observing these IGMP transactions. Protocol Independent Multicast (PIM) is then used between the local and remote multicast routers, to direct multicast traffic from the multicast server to many multicast clients.
IGMP operates above the network layer, though it does not actually act as a transport protocol.
There are three versions of IGMP, as defined by Request for Comments (RFC) documents of the
The CCITT, an international committee that specifies the way modems and fax machines transmit information to ensure compatibility among modems, has classified dial-up modems according to the following modulation standards:
The Point-to-Point Tunneling Protocol (PPTP) is a method for implementing virtual private networks. PPTP uses a control channel over TCP and a GRE tunnel operating to encapsulate PPP packets.
The PPTP specification does not describe encryption or authentication features and relies on the PPP protocol being tunneled to implement security functionality. However the most common PPTP implementation, shipping with the Microsoft Windows product families, implements various levels of authentication and encryption natively as standard features of the Windows PPTP stack. The intended use of this protocol is to provide similar levels of security and remote access as typical VPN products.
A specification for PPTP was published as RFC 2637 and was developed by a vendor consortium formed by Microsoft, Ascend Communications (today part of Alcatel-Lucent), 3Com, and others. PPTP has not been proposed nor ratified as a standard by the IETF.
A PPTP tunnel is instantiated by communication to the peer on TCP port 1723. This TCP connection is then used to initiate and manage a second GRE tunnel to the same peer.
The PPTP GRE packet format is non standard, including an additional acknowledgement field
XHTML (Extensible HyperText Markup Language) is a family of XML markup languages that mirror or extend versions of the widely used Hypertext Markup Language (HTML), the language in which web pages are written.
While HTML (prior to HTML5) was defined as an application of Standard Generalized Markup Language (SGML), a very flexible markup language framework, XHTML is an application of XML, a more restrictive subset of SGML. Because XHTML documents need to be well-formed, they can be parsed using standard XML parsers—unlike HTML, which requires a lenient HTML-specific parser.
XHTML 1.0 became a World Wide Web Consortium (W3C) Recommendation on January 26, 2000. XHTML 1.1 became a W3C Recommendation on May 31, 2001. XHTML5 is undergoing development as of September 2009, as part of the HTML5 specification.
XHTML 1.0 is "a reformulation of the three HTML 4 document types as applications of XML 1.0". The World Wide Web Consortium (W3C) also continues to maintain the HTML 4.01 Recommendation, and the specifications for HTML5 and XHTML5 are being actively developed. In the current XHTML 1.0 Recommendation document, as published and revised to August 2002, the W3C commented that, "The XHTML
Diameter is an authentication, authorization, and accounting protocol for computer networks and an alternative to RADIUS.
Diameter Applications extend the base protocol by adding new commands and/or attributes, such as those for use of the Extensible Authentication Protocol (EAP).
The name is a pun on the RADIUS protocol, which is the predecessor (a diameter is twice the radius). Diameter is not directly backwards compatible but provides an upgrade path for RADIUS. The main differences are the following:
A Diameter Application is not a software application but is a protocol based on the Diameter base protocol (defined in RFC 3588). Each application is defined by an application identifier and can add new command codes and/or new mandatory AVPs. Adding a new optional AVP does not require a new application.
Examples of Diameter applications:
(Generic Bootstrapping Architecture): Bootstrapping Server Function
The Diameter protocol was initially developed by Pat R. Calhoun, Glen Zorn, and Ping Pan in 1998 to provide an Authentication, Authorization, and Accounting (AAA) framework that could overcome the limitations of RADIUS. RADIUS had issues with reliability, scalability, security and
File Transfer Protocol (FTP) is a standard network protocol used to transfer files from one host or to another host over a TCP-based network, such as the Internet.
FTP is built on a client-server architecture and uses separate control and data connections between the client and the server. FTP users may authenticate themselves using a clear-text sign-in protocol, normally in the form of a username and password, but can connect anonymously if the server is configured to allow it. For secure transmission that hides (encrypts) the username and password, and encrypts the content, FTP is often secured with SSL/TLS ("FTPS"). SSH File Transfer Protocol ("SFTP") is sometimes also used instead.
The first FTP client applications were command-line applications developed before operating systems had graphical user interfaces, and are still shipped with most Windows, Unix, and Linux operating systems. Dozens of FTP clients and automation utilities have since been developed for desktops, servers, mobile devices, and hardware, and FTP has been incorporated into hundreds of productivity applications, such as web page editors.
The protocol is specified in RFC 959, which is summarized here.
Network File System (NFS) is a distributed file system protocol originally developed by Sun Microsystems in 1984, allowing a user on a client computer to access files over a network in a manner similar to how local storage is accessed. NFS, like many other protocols, builds on the Open Network Computing Remote Procedure Call (ONC RPC) system. The Network File System is an open standard defined in RFCs, allowing anyone to implement the protocol.
The implementation details are defined in RFC 1094. Sun used version 1 only for in-house experimental purposes. When the development team added substantial changes to NFS version 1 and released it outside of Sun, they decided to release the new version as v2, so that version interoperation and RPC version fallback could be tested.
Version 2 of the protocol (defined in RFC 1094, March 1989) originally operated entirely over UDP. Its designers meant to keep the protocol stateless, with locking (for example) implemented outside of the core protocol. People involved in the creation of NFS version 2 include Rusty Sandberg, Bob Lyon, Bill Joy, and Steve Kleiman.
NFSv2 only allowed the first 2 GB of a file to be read.
Version 3 (RFC 1813, June
The Session Initiation Protocol (SIP) is an IETF-defined signaling protocol widely used for controlling communication sessions such as voice and video calls over Internet Protocol (IP). The protocol can be used for creating, modifying and terminating two-party (unicast) or multiparty (multicast) sessions. Sessions may consist of one or several media streams.
Other SIP applications include video conferencing, streaming multimedia distribution, instant messaging, presence information, file transfer and online games.
The SIP protocol is an Application Layer protocol designed to be independent of the underlying Transport Layer; it can run on Transmission Control Protocol (TCP), User Datagram Protocol (UDP), or Stream Control Transmission Protocol (SCTP). It is a text-based protocol, incorporating many elements of the Hypertext Transfer Protocol (HTTP) and the Simple Mail Transfer Protocol (SMTP).
SIP was originally designed by Henning Schulzrinne and Mark Handley in 1996. In November 2000, SIP was accepted as a 3GPP signaling protocol and permanent element of the IP Multimedia Subsystem (IMS) architecture for IP-based streaming multimedia services in cellular systems. The latest
In computer networking a port is an application-specific or process-specific software construct serving as a communications endpoint in a computer's host operating system. A port is associated with an IP address of the host, as well as the type of protocol used for communication. In plain English, the purpose of ports is to uniquely identify different applications or processes running on a single computer and thereby enable them to share a single physical connection to a packet-switched network like the Internet.
The protocols that primarily use ports are the Transport Layer protocols, such as the Transmission Control Protocol (TCP) and the User Datagram Protocol (UDP) of the Internet Protocol Suite. A port is identified for each address and protocol by a 16-bit number, commonly known as the port number. The port number, added to a computer's IP address, completes the destination address for a communications session. That is, data packets are routed across the network to a specific destination IP address, and then, upon reaching the destination computer, are further routed to the specific process bound to the destination port number.
Note that it is the combination of IP address
The User Datagram Protocol (UDP) is one of the core members of the Internet protocol suite, the set of network protocols used for the Internet. With UDP, computer applications can send messages, in this case referred to as datagrams, to other hosts on an Internet Protocol (IP) network without requiring prior communications to set up special transmission channels or data paths. The protocol was designed by David P. Reed in 1980 and formally defined in RFC 768.
UDP uses a simple transmission model with a minimum of protocol mechanism. It has no handshaking dialogues, and thus exposes any unreliability of the underlying network protocol to the user's program. As this is normally IP over unreliable media, there is no guarantee of delivery, ordering or duplicate protection. UDP provides checksums for data integrity, and port numbers for addressing different functions at the source and destination of the datagram.
UDP is suitable for purposes where error checking and correction is either not necessary or performed in the application, avoiding the overhead of such processing at the network interface level. Time-sensitive applications often use UDP because dropping packets is preferable to
XMODEM is a simple file transfer protocol developed as a quick hack by Ward Christensen for use in his 1977 MODEM.ASM terminal program. XMODEM became extremely popular in the early bulletin board system (BBS) market, largely because it was so simple to implement. It was also fairly inefficient, and as modem speeds increased this problem led to the development of a number of modified versions of XMODEM to improve performance or address other problems with the protocol. Chuck Forsberg collected a number of these into his YMODEM protocol, but poor implementation led to a further fracturing before they were re-unified by his later ZMODEM protocol.
XMODEM, like most file transfer protocols, breaks up the original data into a series of "packets" that are sent to the receiver, along with additional information allowing the receiver to determine whether that packet was correctly received.
The original XMODEM used a 128-byte data packet, the basic block size used on CP/M floppy disks. The packet was prefixed by a simple 3-byte header containing a character, a "block number" from 0-255, and the "inverse" block number—255 minus the block number. Block numbering starts with 1 for the
Address Resolution Protocol (ARP) is a telecommunications protocol used for resolution of network layer addresses into link layer addresses, a critical function in multiple-access networks. ARP was defined by RFC 826 in 1982. It is Internet Standard STD 37. It is also the name of the program for manipulating these addresses in most operating systems.
ARP has been implemented in many combinations of network and overlaying internetwork technologies, such as IPv4, Chaosnet, DECnet and Xerox PARC Universal Packet (PUP) using IEEE 802 standards, FDDI, X.25, Frame Relay and Asynchronous Transfer Mode (ATM), IPv4 over IEEE 802.3 and IEEE 802.11 being the most common cases.
In Internet Protocol Version 6 (IPv6) networks, the functionality of ARP is provided by the Neighbor Discovery Protocol (NDP).
The Address Resolution Protocol is a request and reply protocol that runs encapsulated by the line protocol. It is communicated within the boundaries of a single network, never routed across internetwork nodes. This property places ARP into the Link Layer of the Internet Protocol Suite, while in the Open Systems Interconnection (OSI) model, it is often described as residing between Layers 2 and
Architecture for Control Networks (ACN) is a suite of network protocols for show control developed by Entertainment Services and Technology Association (ESTA). The first official release is formally referred to as ANSI E1.17 - 2006 - Entertainment Technology - Architecture for Control Networks.
It was designed as a replacement for DMX as the control protocol for lighting systems and can be used for controlling more complex devices like video playback servers (media servers) and audio mixers. The protocol is designed to be layered on top of UDP/IP and therefore will run over standard, inexpensive Ethernet and 802.11 (Wi-Fi) network links.
ACN relies on UDP in order to pass its messages. Where reliability is required, the Session Data Transport sub protocol allows semi-reliability of only the latest value for a particular "channel".
ACN defines a number of sub protocols. These protocols all follow the TLV style Protocol Data Units (PDU). These can be nested in predefined hierarchy.
The Protocols defined in ANSI E1.17 are:
There is also an XML description language which defines properties of the devices which is called the Device Description Language.
The ACN protocol may be further
The Cisco Discovery Protocol (CDP) is a proprietary Data Link Layer network protocol developed by Cisco Systems. It is used to share information about other directly connected Cisco equipment, such as the operating system version and IP address. CDP can also be used for On-Demand Routing, which is a method of including routing information in CDP announcements so that dynamic routing protocols do not need to be used in simple network.
Cisco devices send CDP announcements to the multicast destination address 01-00-0c-cc-cc-cc, out each connected network interface. These multicast packets may be received by Cisco switches and other networking devices that support CDP into their connected network interface. This multicast destination is also used in other Cisco protocols such as VTP. By default, CDP announcements are sent every 60 seconds on interfaces that support Subnetwork Access Protocol (SNAP) headers, including Ethernet, Frame Relay and Asynchronous Transfer Mode (ATM). Each Cisco device that supports CDP stores the information received from other devices in a table that can be viewed using the show cdp neighbors command. This table is also accessible via snmp. The CDP table
The Common Gateway Interface (CGI) is a standard (see RFC 3875: CGI Version 1.1) method for web server software to delegate the generation of web content to executable files. Such files are known as CGI scripts; they are programs, often stand-alone applications, usually written in a scripting language.
A web server that supports CGI can be configured to interpret a URL that it serves as a reference to a CGI script. A common convention is to have a cgi-bin/ directory at the base of the directory tree and treat all executable files within it as CGI scripts. Another popular convention is to use filename extensions; for instance, if CGI scripts are consistently given the extension .cgi, the web server can be configured to interpret all such files as CGI scripts.
In the case of HTTP PUT or POSTs, the user-submitted data is provided to the program via the standard input. The web server creates a small and efficient subset of the environment variables passed to it and adds details pertinent to the execution of the program.
The following CGI program shows all the environment variables passed by the web server:
From the environment, we see that the web browser is Firefox running on a
CAN bus (for controller area network) is a vehicle bus standard designed to allow microcontrollers and devices to communicate with each other within a vehicle without a host computer.
CAN bus is a message-based protocol, designed specifically for automotive applications but now also used in other areas such as industrial automation and medical equipment.
Development of CAN bus started originally in 1983 at Robert Bosch GmbH. The protocol was officially released in 1986 at the Society of Automotive Engineers (SAE) congress in Detroit, Michigan. The first CAN controller chips, produced by Intel and Philips, came on the market in 1987. Bosch published the CAN 2.0 specification in 1991.
CAN bus is one of five protocols used in the OBD-II vehicle diagnostics standard. The OBD-II standard has been mandatory for all cars and light trucks sold in the United States since 1996, and the EOBD standard has been mandatory for all gasoline vehicles sold in the European Union since 2001 and all diesel vehicles since 2004.
A modern automobile may have as many as 70 electronic control units (ECU) for various subsystems. Typically the biggest processor is the engine control unit (also engine control
Fiber Distributed Data Interface (FDDI) provides a 100 Mbit/s optical standard for data transmission in a local area network that can extend in range up to 200 kilometers (120 mi). Although FDDI logical topology is a ring-based token network, it does not use the IEEE 802.5 token ring protocol as its basis; instead, its protocol is derived from the IEEE 802.4 token bus timed token protocol. In addition to covering large geographical areas, FDDI local area networks can support thousands of users. As a standard underlying medium it uses optical fiber, although it can use copper cable, in which case it may be referred to as CDDI (Copper Distributed Data Interface). FDDI offers both a Dual-Attached Station (DAS), counter-rotating token ring topology and a Single-Attached Station (SAS), token bus passing ring topology.
FDDI was considered an attractive campus backbone technology in the early to mid 1990s since existing Ethernet networks only offered 10 Mbit/s transfer speeds and Token Ring networks only offered 4 Mbit/s or 16 Mbit/s speeds. Thus it was the preferred choice of that era for a high-speed backbone, but FDDI has since been effectively obsolesced by fast Ethernet which offered
GData (Google Data Protocol) provides a simple protocol for reading and writing data on the Internet, designed by Google. GData combines common XML-based syndication formats (Atom and RSS) with a feed-publishing system based on the Atom Publishing Protocol, plus some extensions for handling queries. It relies on XML or JSON as a data format.
Hypertext Transfer Protocol Secure (HTTPS) is a widely used communications protocol for secure communication over a computer network, with especially wide deployment on the Internet. Technically, it is not a protocol in itself; rather, it is the result of simply layering the Hypertext Transfer Protocol (HTTP) on top of the SSL/TLS protocol, thus adding the security capabilities of SSL/TLS to standard HTTP communications.
In its popular deployment on the internet, HTTPS provides authentication of the web site and associated web server that one is communicating with, which protects against Man-in-the-middle attacks. Additionally, it provides bidirectional encryption of communications between a client and server, which protects against eavesdropping and tampering with and/or forging the contents of the communication. In practice, this provides a reasonable guarantee that one is communicating with precisely the web site that one intended to communicate with (as opposed to an impostor), as well as ensuring that the contents of communications between the user and site cannot be read or forged by any third party.
Because HTTPS piggybacks HTTP entirely on top of TLS, the entirety of the
The Link Layer Discovery Protocol-Media Endpoint Discovery or LLDP-MED is an enhancement to the Link Layer Discovery Protocol (LLDP) that is designed to allow for things such as:
The LLDP-MED protocol was formally approved and published as the standard ANSI/TIA-1057 by the Telecommunications Industry Association (TIA) in April 2006.
The NetWare Core Protocol (NCP) is a network protocol used in some products from Novell, Inc. It is usually associated with the NetWare operating system, but parts of it have been implemented on other platforms such as Linux, Windows NT and various flavors of Unix.
It is used to access file, print, directory, clock synchronization, messaging, remote command execution and other network service functions. TCP/IP and IPX/SPX (obsoleted, technical support is provided only for NetWare platform) are the supported underlying protocols. TCP/IP implementations use TCP/UDP port 524 and rely on SLP for name resolution.
Novell eDirectory uses NCP for synchronizing data changes between the servers in a directory service tree.
The Reverse Address Resolution Protocol (RARP) is an obsolete computer networking protocol used by a host computer to request its Internet Protocol (IPv4) address from an administrative host, when it has available its Link Layer or hardware address, such as a MAC address.
RARP is described in Internet Engineering Task Force (IETF) publication RFC 903. It has been rendered obsolete by the Bootstrap Protocol (BOOTP) and the modern Dynamic Host Configuration Protocol (DHCP), which both support a much greater feature set than RARP.
RARP requires one or more server hosts to maintain a database of mappings of Link Layer addresses to their respective protocol addresses. Media Access Control (MAC) addresses needed to be individually configured on the servers by an administrator. RARP was limited to serving only IP addresses.
Reverse ARP differs from the Inverse Address Resolution Protocol (InARP) described in RFC 2390, which is designed to obtain the IP address associated with a local Frame Relay data link connection identifier. InARP is not used in Ethernet.
Q.What determines network addresses when data link addresses are known?
A: Ping B: ICMP C: ARP D: RARP Correct Answer: D
Samba is a free software re-implementation of the SMB/CIFS networking protocol, originally developed by Andrew Tridgell. As of version 3, Samba provides file and print services for various Microsoft Windows clients and can integrate with a Windows Server domain, either as a Primary Domain Controller (PDC) or as a domain member. It can also be part of an Active Directory domain.
Samba runs on most Unix and Unix-like systems, such as Linux, Solaris, AIX and the BSD variants, including Apple's Mac OS X Server (which was added to the Mac OS X client in version 10.2). Samba is standard on nearly all distributions of Linux and is commonly included as a basic system service on other Unix-based operating systems as well. Samba is released under the GNU General Public License. The name Samba comes from SMB (Server Message Block), the name of the standard protocol used by the Microsoft Windows network file system.
Andrew Tridgell developed the first version of Samba Unix in December 1991 and January 1992, as a PhD student at the Australian National University, using a packet sniffer to do network analysis of the protocol used by DEC Pathworks server software. At the time of the first
The Secure Remote Password protocol (SRP) is an augmented password-authenticated key agreement (PAKE) protocol, specifically designed to work around existing patents.
Like all augmented PAKE protocols, an eavesdropper or man in the middle cannot obtain enough information to be able to brute force guess a password without further interactions with the parties for each guess. This means that strong security can be obtained using weak passwords. Furthermore the server does not store password-equivalent data. This means that an attacker who steals the server data cannot masquerade as the client unless they first perform a brute force search for the password.
The SRP protocol has a number of desirable properties: it allows a user to authenticate themselves to a server, it is resistant to dictionary attacks mounted by an eavesdropper, and it does not require a trusted third party. It effectively conveys a zero-knowledge password proof from the user to the server. In revision 6 of the protocol only one password can be guessed per connection attempt. One of the interesting properties of the protocol is that even if one or two of the cryptographic primitives it uses are attacked, it is
In computer networking, the Stream Control Transmission Protocol (SCTP) is a transport layer protocol, serving in a similar role to the popular protocols Transmission Control Protocol (TCP) and User Datagram Protocol (UDP). It provides some of the same service features of both: it is message-oriented like UDP and ensures reliable, in-sequence transport of messages with congestion control like TCP.
The protocol was defined by the IETF Signaling Transport (SIGTRAN) working group in 2000, and is maintained by the IETF Transport Area (TSVWG) working group. RFC 4960 defines the protocol. RFC 3286 provides an introduction.
In the absence of native SCTP support in operating systems it is possible to tunnel SCTP over UDP, as well as mapping TCP API calls to SCTP ones.
SCTP applications submit their data to be transmitted in messages (groups of bytes) to the SCTP transport layer. SCTP places messages and control information into separate chunks (data chunks and control chunks), each identified by a chunk header. A message can be fragmented over a number of data chunks, but each data chunk contains data from only one user message. SCTP bundles the chunks into SCTP packets. The SCTP packet,
Synchronous Optical Networking (SONET) and Synchronous Digital Hierarchy (SDH) are standardized protocols that transfer multiple digital bit streams over optical fiber using lasers or highly coherent light from light-emitting diodes (LEDs). At low transmission rates data can also be transferred via an electrical interface. The method was developed to replace the Plesiochronous Digital Hierarchy (PDH) system for transporting large amounts of telephone calls and data traffic over the same fiber without synchronization problems. SONET generic criteria are detailed in Telcordia Technologies Generic Requirements document GR-253-CORE. Generic criteria applicable to SONET and other transmission systems (e.g., asynchronous fiber optic systems or digital radio systems) are found in Telcordia GR-499-CORE.
SONET and SDH, which are essentially the same, were originally designed to transport circuit mode communications (e.g., DS1, DS3) from a variety of different sources, but they were primarily designed to support real-time, uncompressed, circuit-switched voice encoded in PCM format. The primary difficulty in doing this prior to SONET/SDH was that the synchronization sources of these various
In telecommunications, a T-carrier, sometimes abbreviated as T-CXR, is the generic designator for any of several digitally multiplexed telecommunications carrier systems originally introduced by Bell Labs around 1960s and used in North America, Japan (Kyoto), and South Korea.
The basic unit of the T-carrier system is the DS0, which has a transmission rate of 64 kbit/s, and is commonly used for one voice circuit. The T-1 channel combines 24 x 64 kbit/s channels into one single channel, using a technique known as Channel Bonding or Channel Aggregation.
The E-carrier system is incompatible with the T-carrier (though cross compliant cards exist) and is used in most locations outside of North America, Japan, Korea.
Existing frequency-division multiplexing carrier systems worked well for connections between distant cities, but required expensive modulators, demodulators and filters for every voice channel. For connections within metropolitan areas, Bell Labs in the late 1950s sought cheaper terminal equipment. Pulse-code modulation allowed sharing a coder and decoder among several voice trunks, so this method was chosen for the T1 system introduced into local use in 1961. In later
Transport Layer Security (TLS) and its predecessor, Secure Sockets Layer (SSL), are cryptographic protocols that provide communication security over the Internet. TLS and SSL encrypt the segments of network connections at the Application Layer for the Transport Layer, using asymmetric cryptography for key exchange, symmetric encryption for confidentiality, and message authentication codes for message integrity.
Several versions of the protocols are in widespread use in applications such as web browsing, electronic mail, Internet faxing, instant messaging and voice-over-IP (VoIP).
TLS is an IETF standards track protocol, last updated in RFC 5246, and is based on the earlier SSL specifications developed by Netscape Communications.
The TLS protocol allows client-server applications to communicate across a network in a way designed to prevent eavesdropping and tampering.
Since most protocols can be used either with or without TLS (or SSL) it is necessary to indicate to the server whether the client is making a TLS connection or not. There are two main ways of achieving this; one option is to use a different port number for TLS connections (for example port 443 for HTTPS). The other is
Trivial File Transfer Protocol (TFTP) is a file transfer protocol notable for its simplicity. It is generally used for automated transfer of configuration or boot files between machines in a local environment. Compared to FTP, TFTP is extremely limited, providing no authentication, and is rarely used interactively by a user.
Due to its simple design, TFTP could be implemented using a very small amount of memory. It is therefore useful for booting computers such as routers which may not have any data storage devices. It is an element of the Preboot Execution Environment (PXE) network boot protocol, where it is implemented in the firmware ROM / NVRAM of the host's network card.
It is also used to transfer small amounts of data between hosts on a network, such as IP phone firmware or operating system images when a remote X Window System terminal or any other thin client boots from a network host or server. The initial stages of some network based installation systems (such as Solaris Jumpstart, Red Hat Kickstart, Symantec Ghost and Windows NT's Remote Installation Services) use TFTP to load a basic kernel that performs the actual installation. It was used for saving router
YMODEM is a protocol for file transfer used between modems. YMODEM was developed by Chuck Forsberg as the successor to XMODEM and MODEM7, and was first implemented in his CP/M YAM program. It was formally given the name "YMODEM" in 1985 by Ward Christensen.
The original YMODEM was essentially the same as XMODEM except that it sent the file's name, size, and timestamp in a regular XMODEM block, "block 0", before actually transferring the file. Sending the file size solved XMODEM's problem of superfluous padding at the end of the file.
Forsberg built the standard with a number of optional features, believing that programmers would want to implement as many as possible on any given platform. He was dismayed to find that the majority of implementations were actually providing nothing more than 1 kilobyte block size with CRC-16, while continuing to use the "YMODEM" name. The result was a large number of mutually incompatible YMODEMs.
YMODEM-1K uses a block size of one kilobyte instead of the standard 128 bytes. 1K blocks were an option in the original YMODEM standard, but this variant is missing the rest of the features, and is best described as a 1k variant of XMODEM.
YMODEM-g is a