





Network Working Group                                          A. Lindem
Request for Comments: 4167                            Cisco Systems, Inc
Category: Informational                                     October 2005


              Graceful OSPF Restart Implementation Report

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

   Graceful OSPF Restart, as specified in RFC 3623, provides a mechanism
   whereby an OSPF router can stay on the forwarding path even as its
   OSPF software is restarted.  This document provides an implementation
   report for this extension to the base OSPF protocol.

Table of Contents

   1. Overview ........................................................2
   2. Implementation Experience .......................................2
      2.1. Implementation Differences .................................2
   3. MIB Reference ...................................................3
   4. Authentication Mechanisms .......................................3
   5. List of Implementations .........................................3
   6. Test Scenarios ..................................................3
   7. Operational Experience ..........................................4
   8. Security Considerations .........................................4
   9. Normative References ............................................4
   10. Informative References .........................................4
   11. Acknowledgments ................................................5













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1.  Overview

   Today, many Internet routers implement a separation of control and
   forwarding functions.  Certain processors are dedicated to control
   and management tasks such as OSPF routing, while other processors
   perform the data forwarding tasks.  This separation creates the
   possibility of maintaining a router's data forwarding capability
   while the router's control software is restarted/reloaded.  For the
   OSPF protocol [OSPF], the protocol mechanisms necessary to accomplish
   this are described in Graceful OSPF Restart [GRACE].

   This document satisfies the RFC 1264 [CRITERIA] requirement for a
   report on implementation experience for Graceful OSPF Restart.
   Section 2 of this document contains the results of an implementation
   survey.  It also documents implementation differences between the
   vendors responding to the survey.  Section 3 contains a MIB
   reference.  Section 4 provide an authentication reference.  Section 5
   simply refers to the implementations listed in section 2.  Section 6
   includes a minimal set of test scenarios.  Finally, section 7
   includes a disclaimer with respect to operational experience.

2.  Implementation Experience

   Eleven vendors have implemented graceful OSPF and have completed the
   implementation survey.  These include Redback, Juniper, Motorola
   Computer Group (formerly Netplane Systems), Mahi Networks, Nexthop
   technologies, Force10 Networks, Procket, Alcatel, Laurel Networks,
   DCL (Data Connection Limited), and Ericsson.  All have implemented
   restart from the perspective of both a restarting and helper router.
   All but one vendor implemented both planned and unplanned restart.
   All implementations are original.  Seven successfully tested
   interoperability with Juniper.  Juniper successfully tested
   interoperability with Force10 Networks.  One vendor tested with John
   Moy's GNU Public License implementation [OSPFD].  Two vendors had not
   tested interoperability at the time of the survey.

2.1.  Implementation Differences

   The first difference was whether strict LSA checking was implemented
   and, if so, whether it was configurable.  In the context of graceful
   OSPF restart, strict LSA checking indicates whether a changed LSA
   will result in the termination of graceful restart by a helping
   router.  Four vendors made it configurable (three defaulted it to
   enabled and one to disabled), another made it a compile option
   (shipping with strict LSA checking disabled), another didn't
   implement it at all, and five implemented strict LSA checking with no
   configuration option to disable it.




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   The second was whether a received grace LSA would be taken to apply
   only to the adjacency on which it was received or to all adjacencies
   with the restarting router.  This is a rather subtle difference since
   it only applies to helping and restarting routers with more than one
   full adjacency at the time of restart.  Eight vendors implemented the
   option of the received grace LSA only applying to the adjacency on
   which it was received.  Three vendors applied the grace LSA to all
   adjacencies with the grace LSA originator (i.e., the restarting
   router).

   The final difference was in whether additional extensions were
   implemented to accommodate other features such as protocol
   redistribution or interaction with MPLS VPNs [VPN].  Five vendors
   implemented extensions and six did not.  It should be noted that such
   extensions are beyond the scope of Graceful OSPF Restart [GRACE].

3.  MIB Reference

   MIB objects for the Graceful OSPF Restart have been added to the OSPF
   Version 2 Management Information Base [OSPFMIB].  Additions include:

   -  Objects ospfRestartSupport, ospfRestartInterval, ospfRestartAge,
      ospfRestartExitReason, and ospfRestartStrictLsaChecking to
      ospfGeneralGroup.

   -  Objects ospfNbrRestartHelperStatus, ospfNbrRestartHelperAge, and
      ospfNbrRestartHelperExitReason to ospfNbrEntry.

   -  Objects ospfVirtNbrRestartHelperStatus,
      ospfVirtNbrRestartHelperAge, and
      ospfVirtNbrRestartHelperExitReason to ospfVirtNbrEntry.

4.  Authentication Mechanisms

   The authentication mechanisms are the same as those implemented by
   the base OSPF protocol [OSPF].

5.  List of Implementations

   Refer to section 2.

6.  Test Scenarios

   A router implementing graceful restart should test, at a minimum, the
   following scenarios as both a restarting and helping router.  For all
   scenarios, monitoring data plane traffic may be used to ensure that
   the restart is non-disruptive:




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   1. Operation over a broadcast network.

   2. Operation over a P2P network.

   3. Operation over a virtual link.

   4. Operation using OSPF MD5 authentication.

   5. Early graceful restart termination when an LSA inconsistency is
      detected.

   6. Early graceful restart termination when a flooded LSA changes (if
      implemented).

7.  Operational Experience

   Since OSPF graceful restart is configurable, it is difficult to gage
   operational experience at this juncture.  However, multiple service
   providers have tested and evaluated it.

8.  Security Considerations

   This document does not discuss implementation and interoperability
   aspects of the security mechanisms in great detail, as no new
   security mechanisms are introduced with Graceful OSPF Restart.
   Security considerations for the OSPF protocol are included in RFC
   2328 [OSPF].  Security considerations for Graceful OSPF Restart are
   included in [GRACE].

9.  Normative References

   [OSPF]      Moy, J., "OSPF Version 2", STD 54, RFC 2328, April 1998.

   [GRACE]     Moy, J., Pillay-Esnault, P., and A. Lindem, "Graceful
               OSPF Restart", RFC 3623, November 2003.

   [CRITERIA]  Hinden, R., "Internet Engineering Task Force Internet
               Routing Protocol Standardization Criteria", RFC 1264,
               October 1991.

10.  Informative References

   [VPN]       Rosen, E. and Y Rekhter, "BGP/MPLS IP VPNs", Work in
               Progress, September 2003.

   [OSPFD]     Moy, J., "OSPF Complete Implementation", Addison-Wesley,
               1991, ISBN 0-201-30966-1




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   [OSPFMIB]   Joyal, D., et al, "OSPF Version 2 Management Information
               Base", Work in Progress, December 2003.

11.  Acknowledgments

   The author wishes to acknowledge the individuals/vendors who have
   completed the implementation survey.

      - Anand Oswal (Redback Networks)
      - Padma Pillay-Esnault (Juniper Networks)
      - Vishwas Manral (Motorola Computer Group, formerly Netplane
        System).
      - Sriganesh Kini (Mahi Networks)
      - Jason Chen (Force10 Networks)
      - Daniel Gryniewicz (NextHop Technologies)
      - Hasmit Grover (Procket Networks)
      - Pramoda Nallur (Alcatel)
      - Ardas Cilingiroglu (Laurel Networks)
      - Philip Crocker (Data Connection Limited)
      - Le-Vinh Hoang (Ericsson)

Author's Address

   Acee Lindem
   Cisco Systems, Inc
   7025 Kit Creek Road
   Research Triangle Park, NC  27709
   USA

   EMail: acee@cisco.com





















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Acknowledgement

   Funding for the RFC Editor function is currently provided by the
   Internet Society.







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