The RIP protocol used with IP is the same used with IPX, and is derived from the same XNS source code. Although RIP was not originally included in the TCP/IP protocol suite, it was included in the free version of UNIX distributed by Berkeley University, and has since become one of the most popular routing protocols in use on TCP/IP networks.
When an IP device comes onto the network, it issues a RIP request to find the addresses of all the routers on the local network. Each of these routers "advertise" routes to other networks that they know about. If the local device is on multiple networks (by way of multiple adapters, or multiple links), and if it is configured to act as a router for those networks, then it will send a RIP update to all of the attached networks, advertising the routes that it too can offer. This process is illustrated in Figure A.16 below:
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RIP routers send these updates every sixty seconds, advertising the routes for every network they know about, so within a few minutes every router on the network will know about every other router on the network. If a router doesn't send out an update within an allotted time, the other routers assume that it is down and remove it from their routing maps.
As networks grow, this becomes an unmanageable and extremely overhead-expensive way to track remote networks. A commonly-used alternative to RIP is OSPF (Open Shortest Path First), which works much better in complex networks. Rather than routers continuously broadcasting information about every other network and router they know of, they only send information about the networks that they are specifically attached to, and only when that information has changed. This minimizes the amount of network traffic used by router advertisements, which greatly reduces the amount of bandwidth required.
For more information on the IP protocol, refer to section A.4.1 Internet Protocol (IP) and Address Resolution Protocol (ARP). For more information on TCP and UDP, refer to section A.4.2 Transmission Control Protocol (TCP) and User Datagram Protocol (UDP) and section A.4.3 IP Sockets and Ports. For more information on name resolution services, refer to section A.4.5 HOSTS Files and the Domain Name Service (DNS). For more information on TCP/IP's mail protocols, refer to Appendix D: SMTP and POP3 Mail.
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