Reliability (computer networking): Difference between revisions

Revision as of 17:26, 18 May 2019

Revision as of 03:26, 5 August 2019

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[[Transmission Control Protocol|TCP]], the main protocol used on the [[Internet]], is a reliable unicast protocol. [[User Datagram Protocol|UDP]] is an unreliable protocol and is often used in [[computer games]], [[streaming media]] or in other situations where speed is an issue and some data loss may be tolerated because of the transitory nature of the data.

Often, a reliable unicast protocol is also [[connection-oriented]]. For example, TCP is connection-oriented, with the [[virtual circuit|virtual-circuit]] ID consisting of source and destination [[IP address]]es and port numbers. However, some unreliable protocols are connection-oriented, such as [[Asynchronous Transfer Mode|ATM]] and [[frameFrame relayRelay]]. In addition, some connectionless protocols, such as [[IEEE 802.11]], are reliable.

==History==

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Meanwhile, the developers of [[CYCLADES]] and of [[ALOHAnet]] demonstrated that it was possible to build an effective computer network without providing reliable packet transmission. This lesson was later embraced by the designers of [[Ethernet]].

If a network does not guarantee packet delivery, then it becomes the host's responsibility to provide reliability by detecting and retransmitting lost packets. Subsequent experience on the ARPANET indicated that the network itself could not reliably detect all packet delivery failures, and this pushed responsibility for error detection onto the sending host in any case. This led to the development of the [[end-to-end principle]], which is one of the [[Internet]]'s fundamental design principles.<!--[[User:Kvng/RTH]]-->

==Reliability properties==

A reliable service is one that notifies the user if delivery fails, while an "''unreliable"'' one does not notify the user if delivery fails.{{cn|reason=See [[Talk:Reliability (computer networking)#Latest revision as of 16:16, 25 October 2017 by Kvng]]|date=November 2017}} For example, [[Internet Protocol|IP]] (IP) provides an unreliable service. Together, [[Transmission Control Protocol|TCP]] (TCP) and [[Internet Protocol|IP]] provide a reliable service, whereas [[User Datagram Protocol|UDP]] (UDP) and [[Internet Protocol|IP]] provide an unreliable one. All these protocols use packets, but [[User Datagram Protocol|UDP]] packets are generally called datagrams.<ref name=kurose>Kurose, James F. & Ross, Keith W. (2007), "Computer Networking: A Top!-Down Approach" {{ISBN|0-321-49770-8}}</ref>{{fv|reason=See [[TalkUser:Reliability (computer networking)#Latest revision as of 16:16, 25 October 2017 by Kvng/RTH]]|date=November 2017}}-->

In the context of distributed protocols, reliability properties specify the guarantees that the protocol provides with respect to the delivery of messages to the intended recipient(s).