RFC 1388 (rfc1388) - Page 2 of 7
RIP Version 2 Carrying Additional Information
Alternative Format: Original Text Document
RFC 1388 RIP Version 2 January 1993
Security Considerations . . . . . . . . . . . . . . . . . . . . . . 7
Author's Address . . . . . . . . . . . . . . . . . . . . . . . . . 7
1. Justification
With the advent of OSPF and IS-IS, there are those who believe that
RIP is obsolete. While it is true that the newer IGP routing
protocols are far superior to RIP, RIP does have some advantages.
Primarily, in a small network, RIP has very little overhead in terms
of bandwidth used and configuration and management time. RIP is also
very easy to implement, especially in relation to the newer IGPs.
Additionally, there are many, many more RIP implementations in the
field than OSPF and IS-IS combined. It is likely to remain that way
for some years yet.
Given that RIP will be useful in many environments for some period of
time, it is reasonable to increase RIP's usefulness. This is
especially true since the gain is far greater than the expense of the
change.
2. Current RIP
The current RIP packet contains the minimal amount of information
necessary for routers to route packets through a network. It also
contains a large amount of unused space, owing to its origins.
The current RIP protocol does not consider autonomous systems and
IGP/EGP interactions, subnetting, and authentication since
implementations of these postdate RIP. The lack of subnet masks is a
particularly serious problem for routers since they need a subnet
mask to know how to determine a route. If a RIP route is a network
route (all non-network bits 0), the subnet mask equals the network
mask. However, if some of the non-network bits are set, the router
cannot determine the subnet mask. Worse still, the router cannot
determine if the RIP route is a subnet route or a host route.
Currently, some routers simply choose the subnet mask of the
interface over which the route was learned and determine the route
type from that.
3. Protocol Extensions
This document does not change the RIP protocol per se. Rather, it
provides extensions to the datagram format which allows routers to
share important additional information.
Malkin