Routing Information Protocol Definition

Routing information protocol (RIP) is a simple interior gateway protocol (IGP) in the TCP/IP (transmission control protocol/Internet protocol) protocol suite that specifies how routers exchange routing table information.

An IGP is a routing protocol that is used to exchange routing information among routers within an autonomous system. An autonomous system is a network, or group of networks, that is controlled by a common administrator (or group of administrators) on behalf of a business, ISP (Internet service provider) or other organization and that presents a common routing policy to the Internet.

RIP is a simple protocol, as it is not concerned with things such as the speed of the links it is connecting or traffic volume on those links. It is a distance vector routing protocol, as opposed to a link state routing protocol, which determines the best packet forwarding paths based solely on minimum distance, typically measured by the hop count (i.e., journeys between routers). A maximum of 15 hops is allowed.

Each RIP router broadcasts (i.e., sends to every device on the network) full routing table updates using UDP (user datagram protocol) every 30 seconds by default, thus generating large amounts of network traffic. A mechanism called split horizon with limited poison reverse is used to avoid routing loops (i.e., the situation in which packets continue to circulate in an endless circle).

An updated version, RIPv2, addresses some of the shortcomings of RIPv1, in part by increasing the amount of information in the packets. For example, it allows use of password authentication to verify routing information and thereby increase security. It also allows a variable-length subnet mask to be given to each destination, thereby permitting an increased number of hosts and subnets on internetworks. In addition, it can use multicasting in place of broadcasting to help reduce bandwidth consumption.

The major advantage of RIP is that it is relatively simple to install and configure. Its disadvantages include slow convergence (i.e., agreement by all routers following a change in the network topology), high bandwidth consumption, a poor scalability as compared to other protocols and a hop limit that restricts the size of networks in which it can be used. Thus, RIP is gradually being replaced by a newer protocol called open shortest path first (OSPF), particularly on larger networks (i.e., those with about 15 or more routers).

Created November 21, 2005.
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