OSPF Protocol Analysis (RFC1245)
Original Publication Date: 1991-Jul-01
Included in the Prior Art Database: 2001-Oct-24
Internet Society Requests For Comment (RFCs)
This is the first of two reports on the OSPF protocol. These reports are required by the IAB/ IESG in order for an Internet routing protocol to advance to Draft Standard Status. OSPF is a TCP/IP routing protocol, designed to be used internal to an Autonomous System (in other words, OSPF is an Interior Gateway Protocol).
Network Working Group J. Moy, Editor
Request for Comments: 1245 Proteon, Inc.
OSPF protocol analysis
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This is the first of two reports on the OSPF protocol. These reports are
required by the IAB/ IESG in order for an Internet routing protocol to
advance to Draft Standard Status. OSPF is a TCP/IP routing protocol,
designed to be used internal to an Autonomous System (in other words,
OSPF is an Interior Gateway Protocol).
Version 1 of the OSPF protocol was published in RFC 1131. Since then
OSPF version 2 has been developed. Version 2 has been documented in RFC
1247. The changes between version 1 and version 2 of the OSPF protocol
are explained in Appendix F of RFC 1247. It is OSPF Version 2 that is
the subject of this report.
This report attempts to summarize the key features of OSPF V2. It also
attempts to analyze how the protocol will perform and scale in the
This document addresses, for OSPF V2, the requirements set forth by the
IAB/IESG for an Internet routing protocol to advance to Draft Standard
state. This requirements are briefly summarized below. The remaining
sections of this report document how OSPF V2 satisfies these
o What are the key features and algorithms of the protocol?
o How much link bandwidth, router memory and router CPU cycles does the
protocol consume under normal conditions?
o For these metrics, how does the usage scale as the routing
environment grows? This should include topologies at least an order
[Moy] [Page 1]
RFC 1245 OSPF protocol analysis July 1991
of magnitude larger than the current environment.
o What are the limits of the protocol for these metrics? (I.e., when
will the routing protocol break?)
o For what environments is the protocol well suited, and for what is it
The OSPF protocol has been developed by the OSPF Working Group of the
Internet Engineering Task Force.
2.0 Key features of the OSPF protocol
This section summarizes the key features of the OSPF protocol. OSPF is
an Internal gateway protocol; it is designed to be used internal to a
single Autonomous System. OSPF uses link-state or SPF-based technology
(as compared to the distance-vector or Bellman-Ford technology found in
routing protocols such as RIP). Individual link state advertisements
(LSAs) describe pieces of the OSPF routing domain (Autonomous System).
These LSAs are flooded throughout the routing domain, forming the link
state database. Each router has an identical link state database;
synchronization of link state databases is maintained via a reliable
flooding algorithm. From this link state database, each router builds a
routing table by calculating a shortest-path tree, with the root of the
tree being the calculating router itself. This cal...