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Detecting Inactive Neighbors over OSPF Demand Circuits (DC) (RFC3883)

IP.com Disclosure Number: IPCOM000031688D
Original Publication Date: 2004-Oct-01
Included in the Prior Art Database: 2004-Oct-05
Document File: 7 page(s) / 13K

Publishing Venue

Internet Society Requests For Comment (RFCs)

Related People

S. Rao: AUTHOR [+3]

Abstract

OSPF is a link-state intra-domain routing protocol used in IP networks. OSPF behavior over demand circuits (DC) is optimized in RFC 1793 to minimize the amount of overhead traffic. A part of the OSPF demand circuit extensions is the Hello suppression mechanism. This technique allows a demand circuit to go down when no interesting traffic is going through the link. However, it also introduces a problem, where it becomes impossible to detect an OSPF-inactive neighbor over such a link. This memo introduces a new mechanism called "neighbor probing" to address the above problem.

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Network Working Group                                             S. Rao

Request for Comments: 3883                                           UTA

Updates: 1793                                                   A. Zinin

Category: Standards Track                                        Alcatel

                                                                  A. Roy

                                                           Cisco Systems

                                                            October 2004

      Detecting Inactive Neighbors over OSPF Demand Circuits (DC)

Status of this Memo

   This document specifies an Internet standards track protocol for the

   Internet community, and requests discussion and suggestions for

   improvements.  Please refer to the current edition of the "Internet

   Official Protocol Standards" (STD 1) for the standardization state

   and status of this protocol.  Distribution of this memo is unlimited.

Copyright Notice

   Copyright (C) The Internet Society (2004).

Abstract

   OSPF is a link-state intra-domain routing protocol used in IP

   networks.  OSPF behavior over demand circuits (DC) is optimized in

   RFC 1793 to minimize the amount of overhead traffic.  A part of the

   OSPF demand circuit extensions is the Hello suppression mechanism.

   This technique allows a demand circuit to go down when no interesting

   traffic is going through the link.  However, it also introduces a

   problem, where it becomes impossible to detect an OSPF-inactive

   neighbor over such a link.  This memo introduces a new mechanism

   called "neighbor probing" to address the above problem.

1.  Motivation

   In some situations, when operating over demand circuits, the remote

   neighbor may be unable to run OSPF [RFC2328], and, as a possible

   result, unable to route application traffic.  Possible scenarios

   include:

   o  The OSPF process might have died on the remote neighbor.

   o  Oversubscription (Section 7 of [RFC1793]) may cause a continuous

      drop of application data at the link level.

Rao, et al.                 Standards Track                     [Page 1]

RFC 3883          OSPF DC Inactive Neighbor Detection       October 2004

   The problem here is that the local router cannot identify problems

   such as this, since the Hello exchange is suppressed on demand

   circuits.  If the topology of the network is such that other routers

   cannot communicate their knowledge about the remote neighbor via

   flooding, the local router and all the...