Network Working Group Padma Pillay-Esnault Internet Draft Juniper Networks January 2004 Category: Standards Track Expires: June 2004 Grace LSA in OSPFv3 draft-pillay-esnault-ospf-v3-grace-lsa-03.txt Status of this Memo This document is an Internet-Draft and is in full conformance with all provisions of Section 10 of RFC2026. Internet-Drafts are working documents of the Internet Engineering Task Force (IETF), its areas, and its working groups. Note that other groups may also distribute working documents as Internet- Drafts. Internet-Drafts are draft documents valid for a maximum of six months and may be updated, replaced, or obsoleted by other documents at any time. It is inappropriate to use Internet-Drafts as reference material or to cite them other than as "work in progress." The list of current Internet-Drafts can be accessed at http://www.ietf.org/ietf/1id-abstracts.txt The list of Internet-Draft Shadow Directories can be accessed at http://www.ietf.org/shadow.html. Copyright Notice Copyright (C) The Internet Society (2002). All Rights Reserved. Abstract This memo describes the OSPF version 3 specific Grace Link State Advertisement used to perform a graceful restart. Pillay-Esnault Standards Track [Page 1] Internet Draft Grace LSA in OSPFv3 January 2004 1. Introduction Graceful OSPF restart [GRACEFUL] describes a mechanism to restart the control plane of an OSPFv2 router which still has its forwarding plane intact with a minimum of disruption to the network. The methods described in [GRACEFUL] work for point to point links for OSPF version 3. In [GRACEFUL] broadcast and point to multipoint links use the Interface Address TLV for OSPF version 2 which is inapplicable in OSPF version 3. This memo describes the new Grace LSA specific to OSPF version 3. 2. The Grace Link State Advertisement The grace-LSA is used by a restarting router to signal its immediate neighbors of its intent to undergo graceful restart and requests his neighbors aid. The grace-LSA contain the restarting router grace-period and information on the reason of initiating the restart process. The neighbors helper role consists of continuing to advertise the restarting router as FULL for the specified grace period left regardless of the actual neighbor state. In OSPF version 3, the Designated router is identified by its router-id as opposed to its interface address in OSPF version 2 on a broadcast segment. The grace-LSA for OSPF version 2 carries the interface address of the restarting router for the helper to identify the restarting neighbor per [GRACEFUL]. Broadcast and point-to-multi-point segments do not need to carry a TLV is added to carry the router ID for a broadcast segment in OSPF version 3 as the Designated Router can be identified for the advertising router of the grace-LSA. In essence, there is no equivalent router-address TLV for OSPF version 3 and it is not needed. The grace-LSA body format will remain the same as described in [GRACEFUL]. Pillay-Esnault Standards Track [Page 2] Internet Draft Grace LSAs in OSPFv3 October 2002 2.1 Grace LSA version 3 - LS Type A grace-LSA is defined as link-local scope LSA with the LS type equal to 0x000b. LSA function code LS Type Description -------------------------------------------------------------------- 11 0x000b Grace LSA The U-bit is set to 0 to indicate that this is a Link Local LSA The S2-bit and S1-bit are also both set to 0 to indicate a link-local scope. 2.2 Grace LSA Format This grace LSA format is as follows 0 1 2 3 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | LS age |0|0|0| 11 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Link State ID | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Advertising Router | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | LS sequence number | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | LS checksum | Length | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | | +- TLVs -+ | ... | The Link State ID of a grace-LSA in OSPF version 3 is the interface ID of the interface the LSA is originated on. The format of the TLVs within the body of a grace-LSA is the same as the TLV format used by the Traffic Engineering Extensions to OSPF [OSPF-TE]. The TLV header consists of a 16-bit Type field and a 16-bit length field, and is followed by zero or more bytes of value. The length field indicates the length of the value portion in bytes. The value portion is padded to four-octet alignment, but the padding is not included in the length field. Pillay-Esnault Standards Track [Page 3] Internet Draft Grace LSAs in OSPFv3 January 2004 The following is the list of TLVs that can appear in the body of a grace-LSA. o Grace Period (Type=1, length=4). The number of seconds that the router's neighbors should continue to advertise the router as fully adjacent, regardless of the the state of database synchronization between the router and its neighbors. This TLV is mandatory in a Grace LSA. o Graceful restart reason (Type=2, length=1). Encodes the reason for the router restart, as one of the following: 0 (unknown), 1 (software restart), 2 (software reload/upgrade) or 3 (switch to redundant control processor). This TLV is mandatory in a grace-LSA. Pillay-Esnault Standards Track [Page 4] Internet Draft Grace LSAs in OSPFv3 January 2004 Normative References [OSPFv3] Coltun, R., D. Ferguson, and J. Moy, "OSPF for IPv6", RFC 2740, December 1999 [GRACEFUL] Moy J., Pillay-Esnault P., Lindem A., "Graceful OSPF Restart", RFC 3623, November 2003. [OSPF-TE] Katz, D., D. Yeung and K. Kompella, "Traffic Engineering Extensions to OSPF", RFC 3630, September 2003 Security Considerations The OSPF v3 security mechanisms to prevent tampering and spoofing of LSAs suffice. Acknowledgments Many thanks to Kireeti Kompella with whom much of this was discussed. The author also wish to thank Acee Lindem and Kunihiro Ishiguro for their comments. Authors' Addresses Padma Pillay-Esnault Juniper Networks, Inc. 1194 N. Mathilda Ave Sunnyvale, CA 94089 Email: padma@juniper.net Pillay-Esnault Standards Track [Page 5] Internet Draft Grace LSA in OSPFv3 January 2004 IPR Notice The IETF takes no position regarding the validity or scope of any intellectual property 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; neither does it represent that it has made any effort to identify any such rights. Information on the IETF's procedures with respect to rights in standards-track and standards-related documentation can be found in BCP-11. Copies of claims of rights made available for publication 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 implementors or users of this specification can be obtained from the IETF Secretariat. 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