Overview RIP
Overview of RIP
1. uses the shortest path computation algorithm known as the Bellman-Ford algorithm2
2. routers exchange routing information with their neighbors in the form of routing updates
3. The use of RIP in IP networks is specified and standardized by three Requests for Comment (RFCs):
RFC 1058, “Routing Information Protocol”
RFC 2082, “RIP-2 MD5 Authentication”
RFC 2453, “RIP Version 2”
RIP Features
1. use UDP (User Datagram Protocol) port 520
2. RIP routers exchange packets with their neighbors; the packets contain network addresses and an associated metric, or hop count, to reach those addresses.
3. The metric (hop count) is a measure of the distance from the source of the update to the destination network
4. sends messages to the broadcast address (255.255.255.255)
5. update messages at regular intervals (30 seconds)
6. uses an infinity metric to prevent routing loops
RIP Operations
1. Request messages and Response messages
2. a Request message has a single entry in it with a metric of 16 and an address family identifier field that contains all zeros
3. A RIP router receives Response messages for one of three different reasons:
1. In response to a Request message generated by the local router
2. A regular (unsolicited) Response message sent by a neighbor
3. A triggered update Response message sent by a neighbor
Stability Features
1. Split Horizon: split horizon prevents the local router from including any routes learned from a neighbor on the interface from which the message is being sent out
2. Split Horizon with Poisoned Reverse:
Triggered Updates
In this case, a topology change for the local router will be announced immediately to all active neighbors. Each downstream RIP router will in turn send an almost immediate update to
its neighbors using triggered updates.
Hold-Downs
it prevents the propagation of bad routing information throughout the network. The Hold-Down timer is used when an update is received by the local router that contains a route from a peer with a higher metric (other than infinity) than
the one in the current routing table
Timers
RIP uses a number of timers in its operation, among them the Update timer, the Hold-Down timer, the Timeout timer, and the Garbage Collection timer.