OSPF Refresh and Flooding Reduction in Stable Topologies (RFC4136)
Original Publication Date: 2005-Jul-01
Included in the Prior Art Database: 2005-Jul-29
Internet Society Requests For Comment (RFCs)
This document describes an extension to the OSPF protocol to reduce periodic flooding of Link State Advertisements (LSAs) in stable topologies.
Network Working Group P.
Request for Comments: 4136 Cisco Systems
Category: Informational July 2005
OSPF Refresh and Flooding Reduction in Stable Topologies
Status of 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 (C) The Internet Society (2005).
describes an extension to the OSPF protocol to reduce
periodic flooding of Link State Advertisements (LSAs) in stable
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.
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.
Providers and users that have large networks have
noticed non-negligible protocol traffic, even when their network
topologies were stable.
every LSA to be refreshed every 1800 seconds or else
they will expire when they reach 3600 seconds .
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
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" .
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...