RIPv2 analysis: RIP Version 2 Protocol Analysis
A report card for RIP-2: what is new, who has implemented it, and how it fared in real use.
Malkin, G., "RIP Version 2 Protocol Analysis", RFC 1721, DOI 10.17487/RFC1721, November 1994, <https://www.rfc-editor.org/info/rfc1721>.
@misc{rfc1721,
series = {Request for Comments},
number = 1721,
howpublished = {RFC 1721},
publisher = {RFC Editor},
doi = {10.17487/RFC1721},
url = {https://www.rfc-editor.org/info/rfc1721},
author = {G. Malkin},
title = {{RIP Version 2 Protocol Analysis}},
pagetotal = 4,
year = 1994,
month = nov,
} RFC text
Contents
Network Working Group G. Malkin
Request for Comments: 1721 Xylogics, Inc.
Obsoletes: 1387 November 1994
Category: Informational
RIP Version 2 Protocol Analysis
Status of this Memo
This memo provides information for the Internet community. This memo
does not specify an Internet standard of any kind. Distribution of
this memo is unlimited.
Abstract
As required by Routing Protocol Criteria (RFC 1264), this report
documents the key features of the RIP-2 protocol and the current
implementation experience. This report is a prerequisite to
advancing RIP-2 on the standards track.
Acknowledgements
The RIP-2 protocol owes much to those who participated in the RIP-2
working group. A special thanks goes to Fred Baker, for his help on
the MIB, and to Jeffrey Honig, for all his comments.
1. Protocol Documents
The RIP-2 applicability statement is defined in RFC 1722 [1].
The RIP-2 protocol description is defined in RFC 1723 [2]. This memo
obsoletes RFC 1388, which specifies an update to the "Routing
Information Protocol" RFC 1058 (STD 34).
The RIP-2 MIB description is defined in RFC 1724 [3]. This memo
obsoletes RFC 1389.
2. Key Features
While RIP-2 shares the same basic algorithms as RIP-1, it supports
several new features. They are: external route tags, subnet masks,
next hop addresses, and authentication.
The significant change from RFC 1388 is the removal of the domain
field. There was no clear agreement as to how the field would be
used, so it was determined to leave the field reserved for future
expansion.
2.1 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.
2.2 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.
2.3 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.
2.4 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.
2.5 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 are per-peer counters which provide the
status of RIP-2 "neighbors".
The MIB was modified to deprecate the domain, which was removed from
the protocol. It has also been converted into version 2 format.
4. Implementations
Currently, there are three complete implementations of RIP-2: GATED,
written by Jeffrey Honig at Cornell University; Xylogics's Annex
Communication server; and an implementation for NOS, written by Jeff
White. The GATED implementation is available by anonymous FTP from
gated.cornell.edu as pub/gated/gated-alpha.tar.Z. The implementation
for NOS is available by anonymous FTP from ucsd.edu as
/hamradio/packet/tcpip/incoming/rip2.zip.
Additionally, Midnight Networks has produced a test suite which
verifies an implementation's conformance to RFC 1388 implemented over
RFC 1058.
The author has conducted interoperability testing between the GATED
and Xylogics implementations and found no incompatibilities. This
testing includes verification of protection provided by the
authentication mechanism described in section 2.4.
5. Operational experience
Xylogics has been running RIP-2 on its production systems for five
months. The topology includes seven subnets in a class B address and
various, unregistered class C addresses used for dial-up access. Six
systems, in conjunction with three routers from other vendors and
dozens of host systems, operate on those subnets.
The only problem which has appeared is the reaction of some routers
to Version 2 RIP packets. Contrary to RFC 1058, these routers
discard Version 2 packets rather than ignoring the fields not defined
for Version 1.
6. References
[1] Malkin, G., "RIP Version 2 Protocol Applicability Statement", RFC
1722, Xylogics, Inc., November 1994.
[2] Malkin, G., "RIP Version 2 - Carrying Additional Information",
RFC 1723, Xylogics, Inc., November 1994.
[3] Malkin, G., and F. Baker, "RIP Version 2 MIB Extension", RFC
1724, Xylogics, Inc., Cisco Systems, November 1994.
7. Security Considerations
Security issues are discussed in sections 2.4 and 4.
8. Author's Address
Gary Scott Malkin
Xylogics, Inc.
53 Third Avenue
Burlington, MA 01803
Phone: (617) 272-8140
EMail: gmalkin@Xylogics.COM
AI ELI5
On this page
§1Protocol Documents
As required by RFC 1264, this report documents the key features of RIP-2 and the implementation experience so far. It does not specify a standard.
The pieces of RIP-2 are defined elsewhere: the applicability statement in RFC 1722, the protocol description in RFC 1723, and the MIB in RFC 1724. The memo says it obsoletes RFC 1388, which updated the Routing Information Protocol of RFC 1058, and RFC 1389 for the MIB.
This is a short report that points to the main rulebooks for a routing system and says why the report was needed.
§2Key Features
RIP-2 shares the same basic algorithms as RIP-1 but adds external route tags, subnet masks, next hop addresses and authentication, and allows multicasting. The significant change from RFC 1388 is the removal of the domain field, which was left reserved for future expansion because there was no clear agreement on how to use it.
The route tag may carry information acquired from an EGP, such as an AS number, but its contents are beyond the protocol's scope. Subnet masks allow variable subnet masks and are needed for classless addressing as the CIDR work proposes. A next hop address lets a router tell others that a better next hop than itself exists, for example when another IGP runs on the same network.
Authentication uses the same extensible mechanism as OSPF, though only a plain-text password is defined so far. RIP-2 packets may be multicast instead of broadcast, which reduces the load on hosts that do not run routing protocols and avoids RIP-1 routers misreading routes whose subnet mask they cannot apply.
The new version adds name tags for routes, a way to say how big each neighborhood is, shortcut hints, a secret password, and quieter announcements.
§3The RIP-2 MIB
The MIB allows monitoring and control of RIP's operation inside the router. It has global and per-interface counters and controls, plus per-peer counters that show the status of RIP-2 neighbors. It was changed to deprecate the domain, which was removed from the protocol, and converted to version 2 format.
It is a dashboard with counters that lets an operator see how the router and its neighbors are doing.
§4Implementations and Experience
The memo names three complete implementations: GATED, written by Jeffrey Honig at Cornell University; Xylogics's Annex Communication server; and one for NOS, written by Jeff White. The author tested GATED against the Xylogics implementation, found no incompatibilities, and verified the protection offered by authentication.
Xylogics had run RIP-2 on its production systems for five months on a topology with seven subnets in a class B address. The only problem was that some routers discard Version 2 packets rather than ignoring the fields not defined for Version 1, contrary to RFC 1058. The security considerations simply point back to the authentication and implementation sections.
Three teams built it, they tried it with each other, and it worked, except a few older routers threw away the new messages instead of ignoring the new parts.