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.
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.
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.
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.
Lindem Informational [Page 2]
RFC 4167 Graceful OSPF Restart Implementation Report October 2005
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].
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:
Lindem Informational [Page 3]
RFC 4167 Graceful OSPF Restart Implementation Report October 2005
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.
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].
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
Full Copyright Statement
Copyright (C) The Internet Society (2005).
This document is subject to the rights, licenses and restrictions contained in BCP 78, and except as set forth therein, the authors retain all their rights.
This document and the information contained herein are provided on an "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY AND THE INTERNET ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.
Intellectual Property
The IETF takes no position regarding the validity or scope of any Intellectual Property Rights or other rights that might be claimed to pertain to the implementation or use of the technology described in this document or the extent to which any license under such rights might or might not be available; nor does it represent that it has made any independent effort to identify any such rights. Information on the procedures with respect to rights in RFC documents can be found in BCP 78 and BCP 79.
Copies of IPR disclosures made to the IETF Secretariat and any assurances of licenses to be made available, or the result of an attempt made to obtain a general license or permission for the use of such proprietary rights by implementers or users of this specification can be obtained from the IETF on-line IPR repository at http://www.ietf.org/ipr.
The IETF invites any interested party to bring to its attention any copyrights, patents or patent applications, or other proprietary rights that may cover technology that may be required to implement this standard. Please address the information to the IETF at ietf- ipr@ietf.org.
Acknowledgement
Funding for the RFC Editor function is currently provided by the Internet Society.