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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

Lindem Informational [Page 5] RFC 4167 Graceful OSPF Restart Implementation Report October 2005

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Acknowledgement

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

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