routing information protocol (RIP)
Routing works with routing tables, which are created manually for static routing, and learned by the routers and created afterwards for dynamic ro uting. Routing Information Protocol( RIP) works with Distance Vector algorithm and is the most frequently used Interior Routing Protocol( IRP). It was developed on the basis of the XNS RIP. It has established itself as the standard module of the Berkeley Software Distribution( BSD) under Unix 4.x.
With the RIP protocol, all routers send their own routing tables as a broadcast to the other routers at intervals. The distance to other networks is thereby indicated in relation, i.e. from the view of the own routing table. Based on the received tables, the routers calculate the shortest transmitted distances to each destination network and take the neighbor router that advertised this distance as the destination router for forwarding. The maximum distance may be 15 hops, the value 16 is called Infinity and says that the value is not reachable.
The RIP protocol comes in two versions: version 2 of RIP, RIPv2, is built on the Distance Vector algorithm and, like RIPv1, uses the User Datagram Protocol( UDP) to transport routing tables. The headers of both protocols have identical lengths. RIPv2 uses the unused data fields of the header in version 1 for the specification of the subnets (Subnet Mask, 4 octets) and the entry for the next hop (Next Hop, 4 octets). This specification determines the next address through which the data packet must pass. In the data field Metric Count the hop counter is kept. Each time the data packet passes through a router, the Metric Count is incremented by one counter unit. The maximum value is 16 and means that the network is no longer accessible.
The Routing Information Protocol is specified by the Internet Engineering Task Force( IETF) and described in RFC 1058. For IPv6, it is described under RFC 2080 and in the RIP2 version in RFC 2453.