RFC 2081 (rfc2081) - Page 2 of 4
RIPng Protocol Applicability Statement
Alternative Format: Original Text Document
RFC 2081 RIP-2 Applicability January 1997 3. Applicability A goal in developing RIPng was to make the minimum necessary change to RIP-2 to produce RIPng. In essence, the IPv4 address was expanded into an IPv6 address, the IPv4 subnet mask was replaced with an IPv6 prefix length, the next-hop field was eliminated but the functionality has been preserved, and authentication was removed. The route tag field has been preserved. The maximum diameter of the network (the maximum metric value) is 15; 16 still means infinity (unreachable). The basic RIP header is unchanged. However, the size of a routing packet is no longer arbitrarily limited. Because routing updates are never forwarded, the routing packet size is now determined by the physical media and the sizes of the headers which precede the routing data (i.e., media MTU minus the combined header lengths). The number routes which may be included in a routing update is the routing data length divided by the size of a routing entry. 3.1 Prefix The address field of a routing entry is 128 bits in length, expanded from the 32 bits available in RIP-2. This allows the RIP entry to carry an IPv6 prefix. 3.2 Prefix Length The 32-bit RIP-2 subnet mask field is replaced by an 8-bit prefix length field. It allows the specification of the number of bits in the prefix which form the actual prefix. 3.3 Next Hop The ability to specify the next hop, rather than simply allowing the recipient of the update to set the next hop to the sender of the update, allows for the elimination of unnecessary hops through routers which are running multiple routing protocols. Consider following example topology: ----- ----- ----- ----- |IR1| |IR2| |XR1| |XR2| --+-- --+-- --+-- --+-- | | | | --+-------+-------------+-------+-- |--------RIPng--------| Malkin Informational
