RFC1387 - RIP Version 2 Protocol Analysis

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　　Network Working Group G. Malkin
Request for Comments: 1387 Xylogics, Inc.
January 1993

RIP Version 2 Protocol Analysis

Status of this Memo

This memo provides information for the Internet community. It does

not specify an Internet standard. Distribution of this memo is
unlimited.

Abstract

As required by Routing Protocol Criteria (RFC1264), this report
documents the key features of the RIP-2 protocol and the current
implementation experience.

Acknowledgements

The RIP-2 protocol owes much to those who participated in the RIP-2
Working Group of the Internet Engineering Task Force (IETF). A
special thanks goes to Fred Baker for his help on the MIB, and to
Jeffrey Honig for the implementation experience.

1. Protocol Documents

The RIP-2 protocol description is defined in RFC1388 [1]. This memo
suggests an update to the "Routing Information Protocol" (RFC1058)
[3]. The RIP-2 MIB description is defined in RFC1389 [2].

2. Key Features

While RIP-2 shares the same basic algorithms as RIP-1, it supports
several new features. They are: routing domains, external route
tags, subnet masks, next hop addresses, and authentication.

2.1 Routing Domains

Routing domains allow multiple RIP "clouds" to exist over the same
physical network. This is a feature requested by several members of
the working group. It allows simple policies to be constructed by
grouping routers into domains which share routing information.

2.2 External Route Tags

The route tag field may be used to propagate information acquired
from an EGP. The definition of the contents of this field are beyond
the scope of this protocol. However, it may be used, for example, to
propagate an EGP AS number.

2.3 Subnet Masks

Inclusion of subnet masks was the original intent of opening the RIP
protocol for improvement. Subnet mask information makes RIP more
useful in a variety of environments and allows the use of variable
subnet masks on the network. Subnet masks are also necessary for
implementation of "classless" addressing, as the CIDR work proposes.

2.4 Next Hop Addresses

Support for next hop addresses allows for optimization of routes in
an environment which uses multiple routing protocols. For example,
if RIP-2 were being run on a network along with another IGP, and one
router ran both protocols, then that router could indicate to the
other RIP-2 routers that a better next hop than itself exists for a
given destination.

2.5 Authentication

One significant improvement RIP-2 offers over RIP-1, is the addition
of an authentication mechanism. Essentially, it is the same
extensible mechanism provided by OSPF. Currently, only a plain-text
password is defined for authentication. However, more sophisticated
authentication schemes can easily be incorporated as they are
defined.

2.6 Multicasting

RIP-2 packets may be multicast instead of being broadcast. The use
of an IP multicast address reduces the load on hosts which do not
support routing protocols. It also allows RIP-2 routers to share
information which RIP-1 routers cannot hear. This is useful since a
RIP-1 router may misinterpret route information because it cannot
apply the supplied subnet mask.

3. RIP-2 MIB

The MIB for RIP-2 allows for monitoring and control of RIP's
operation within the router. In addition to global and per-interface
counters and controls, there is are per-peer counters which provide
the status of RIP-2 "neighbors".

4. Implementations

Currently, there is one nearly complete implementation of RIP-2. A
"gated" implementation is now available with RIP-2, written by
Jeffrey Honig at Cornell University. It may be acquired by anonymous
FTP from gated.cornell.edu as pub/gated/gated-alpha.tar.Z. It
implements multicasting, subnet masks, limited authentication, next-
hop, and limited routing domain support. A RIP-2 version of ripquery
is also available. The "gated" implementation does not yet support
full subsumption rules, full authentication, full routing domains,
and the MIB. It has been tested against itself and various RIP-1
implementations.

A second, complete implementation is under development by a vendor
who's identity cannot be disclosed at this time.

5. References

[1] Malkin, G., "RIP Version 2 - Carrying Additional Information",
RFC1388, Xylogics, Inc., January 1993.

[2] Malkin, G., and F. Baker, "RIP Version 2 MIB Extension", RFC
1389, Xylogics, Inc., Advanced Computer Communications, January
1993.

[3] Hedrick, C., "Routing Information Protocol", RFC1058, Rutgers
University, June 1988.

6. Security Considerations

Security issues are discussed in section 2.5.

7. Author's Address

Gary Scott Malkin
Xylogics, Inc.
53 Third Avenue
Burlington, MA 01803

Phone: (617) 272-8140
EMail: gmalkin@Xylogics.COM

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