Routing Protocols provide the functionality of Route assignment i.e. the selection of routes or paths between origins and destinations in transportation networks. They select reliable and cost effective transmission paths from the multiple paths that are available over a transporattion network. There are two types of Routing protocols and they are 1. IGP (Interior gateway protocol) A set of routing protocols that are used within an autonomous system. 2. EGP (Exterior gateway protocol) They interconnect different autonomous systems. Now about RIP or Routing Information Protocol : RIP is a commonly used interior gateway protocol. It is still actively used in the networks but is being replaced by other routing protocols like OSPF and IGRP. The standard version of RIP, IP RIP, is formally defined in the two documents, RFC 1058 and STD 56. RIP is a distance-vector routing protocol, which employs the hop count as a routing metric. The maximum number of hops allowed with RIP is 15, and the hold down time is 120 seconds. Each RIP router transmits full updates every 30 seconds by default, generating large amounts of network traffic in lower bandwidth networks. It runs above the network layer of the Internet protocol suite, using UDP port 520 to carry its data. RIP sends routing-update messages at regular intervals and when the network topology changes. When a router receives a routing update that includes changes to an entry, it updates its routing table to reflect the new route. The metric value for the path is increased by 1, and the sender is indicated as the next hop. RIP routers maintain only the best route (the route with the lowest metric value) to a destination. After updating its routing table, the router immediately begins transmitting routing updates to inform other network routers of the change. These updates are sent independently of the regularly scheduled updates that RIP routers send. RIP uses numerous timers to regulate its performance. These include a routing-update timer, a route-timeout timer, and a route-flush timer. The routing-update timer clocks the interval between periodic routing updates (default of 30 secs). Each routing table entry has a route-timeout timer associated with it. When the route-timeout timer expires, the route is marked invalid but is retained in the table until the route-flush timer expires. RIP prevents routing loops from continuing indefinitely by implementing a limit on the number of hops allowed in a path from the source to a destination. The maximum number of hops in a path is 15. If a router receives a routing update that contains a new or changed entry, and if increasing the metric value by 1 causes the metric to be infinity (that is, 16), the network destination is considered unreachable. The downside of this stability feature is that it limits the maximum diameter of a RIP network to less than 16 hops. RIP includes a number of other stability features like split horizon and holddown mechanisms to prevent incorrect routing information from being propagated. RIP uses the Bellman-Ford algorithm for routing purposes. The three versions of RIP are RIPv1 (RFC 1058),RIPv2 (RFC 2453) and RIPng (RFC 2080). The RIPng is meant as a protocol for IPv6 implementations.

``Routing protocols'' lists the following about routing protocols: * routing protocols supported by SCO TCP/IP * whether the protocol is designed for exchanging information about networks interior to or exterior to an autonomous system * the routing daemon(s) in SCO TCP/IP that supports the protocol * whether the protocol is typically run on a router or nonrouter * typical size of the network on which the protocol is most useful * any distinguishing features of the protocol. Hope it helps you.