RIP (Routing Information Protocol) is derived from the Xerox Network Systems (XNS) routing protocol. RIP was in widespread use for several years before being standardized in RFC 1058. A second version was proposed in 1993 and improved in 1994. RIP computes routes using a simple distance vector routing algorithm. Every hop in the network is assigned a cost (usually 1). The total metric for a path is the sum of the hop costs. RIP chooses the next hop so that datagrams will follow a least-cost path.
RIP’s strong points are its simplicity. Often there is no reason to use more functional-and complicated-methods for a small network or a network with a simple topology. However, for large, complex networks, RIP has some serious shortcomings. For example:
- The maximum metric for any path is 15. Sixteen means “I can’t get there!” Because it is easy to run out of hops on a big network, RIP usually is configured with a cost of 1 for each hop, whether that hop is a slow dialup or a high-speed fiber link.
- After a disruption in the network, RIP often is slow to reestablish optimal routes. In fact, after disruption, datagram traffic may run around in circles for a while.
- RIP cannot respond to changes in delay or load across links. It cannot split traffic to balance the load.