RIP Overview, History, Standards and Versions
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The Routing Information Protocol (RIP) has been the most popular interior routing protocol in the TCP/IP suite for many years. The history of the protocol and how it came to achieve prominence is a rather interesting one. Unlike many of the other important protocols in the TCP/IP suite, RIP was not first developed formally using the RFC standardization process. Rather, it evolved as a de facto industry standard and only became an Internet standard later on.
The history of RIP shares some commonality with that of another networking heavyweight: Ethernet. Like the formidable LAN technology, RIP's roots go back to that computing pioneer, Xerox's Palo Alto Research Center (PARC). At the same time that Ethernet was being developed for tying together local area networks, PARC created a higher layer protocol to run on Ethernet called the Xerox PARC Universal Protocol (PUP). PUP required a routing protocol, so Xerox created a protocol called the Gateway Information Protocol (GWINFO). This was later renamed the Routing Information Protocol and used as part of the Xerox Network System (XNS) protocol suite.
RIP entered the mainstream when developers at the University of California at Berkeley adapted it for use in the Berkeley Standard Distribution (BSD) of the UNIX operating system. RIP first appeared in BSD version 4.2 in 1982, where it was implemented as the UNIX program routed (pronounced route-dee, not rout-edthe d stands for daemon, a common UNIX term for a server process.)
BSD was (and still is) a very popular operating system, especially for machines connected to the early Internet. As a result, RIP was widely deployed and became the industry standard for internal routing protocols. It was used both for TCP/IP and also other protocol suites. In fact, a number of other routing protocols, such as the RTP protocol in the AppleTalk suite, were based on this early version of RIP.
For a while, the BSD implementation of routed was actually considered the standard for the protocol itself. However, this was not a formally defined standard, and this meant there was no formal definition of how exactly it functioned. This lead to slight differences in various implementations of the protocol over time. To resolve potential interoperability issues between implementations, the IETF formally specified RIP in the Internet standard RFC 1058, Routing Information Protocol, published in June 1988. This RFC was based directly on the BSD routed program. This original version of RIP is now also sometimes called RIP version 1 or RIP-1 to differentiate it from later versions.
RIP's popularity was due in large part to its inclusion in BSD; this was in turn a result of the relative simplicity of the protocol. RIP uses the distance-vector algorithm (also called the Bellman-Ford algorithm after two of its inventors) to determine routes. Each router maintains a routing table containing entries for various networks or hosts in the internetwork. Each entry contains two primary pieces of information: the address of the network or host, and the distance to it, measured in hops, which is simply the number of routers that a datagram must pass through to get to its destination.
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