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OSPF Refresh and Flooding Reduction in Stable Topologies (RFC4136)

IP.com Disclosure Number: IPCOM000126695D
Original Publication Date: 2005-Jul-01
Included in the Prior Art Database: 2005-Jul-29
Document File: 6 page(s) / 9K

Publishing Venue

Internet Society Requests For Comment (RFCs)

Related People

P. Pillay-Esnault: AUTHOR

Abstract

This document describes an extension to the OSPF protocol to reduce periodic flooding of Link State Advertisements (LSAs) in stable topologies.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 33% of the total text.

Network Working Group                                  P. Pillay-Esnault
Request for Comments: 4136                                 Cisco Systems
Category: Informational                                        July 2005


        OSPF Refresh and Flooding Reduction in Stable Topologies

Status of This Memo

   This memo provides information for the Internet community.  It does
   not specify an Internet standard of any kind.  Distribution of this
   memo is unlimited.

Copyright Notice

   Copyright (C) The Internet Society (2005).

Abstract

   This document describes an extension to the OSPF protocol to reduce
   periodic flooding of Link State Advertisements (LSAs) in stable
   topologies.

   Current OSPF behavior requires that all LSAs, except DoNotAge LSAs,
   to be refreshed every 30 minutes.  This document proposes to
   generalize the use of DoNotAge LSAs in order to reduce protocol
   traffic in stable topologies.

1.  Introduction

   The explosive growth of IP-based networks has placed focus on the
   scalability of Interior Gateway Protocols such as OSPF.  Networks
   using OSPF are growing every day and will continue to expand to
   accommodate the demand for connections to the Internet or intranets.

   Internet Service Providers and users that have large networks have
   noticed non-negligible protocol traffic, even when their network
   topologies were stable.

   OSPF requires every LSA to be refreshed every 1800 seconds or else
   they will expire when they reach 3600 seconds [1].

   This document proposes to overcome the LSA expiration by generalizing
   the use of DoNotAge LSAs.  This technique will facilitate OSPF
   scaling by reducing OSPF traffic overhead in stable topologies.


Pillay-Esnault               Informational                      [Page 1]
RFC 4136          OSPF Refresh and Flooding Reduction          July 2005


2.  Changes in the Existing Implementation

   This enhancement relies on the implementation of the DoNotAge bit and
   the Indication-LSA.  The details of the implementation of the
   DoNotAge bit and the Indication-LSA are specified in "Extending OSPF
   to Support Demand Circuits" [2].

   Flooding-reduction-capable routers will continue to send hellos to
   their neighbors and keep aging their self-originated LSAs in their
   database.  However, these routers will flood their self-originated
   LSAs with the DoNotAge bit set.  Thus, self-originated LSAs do not
   have to be re-flooded every 30 minutes and the re-flooding interval
   can be extended to the configured forced-flooding interval.  As in
   normal OSPF operation, any change in the contents of the LSA will
   cause a reoriginated LSA to be flooded with the DoNotAge bit set.
   This will reduce protocol traffic o...