Network Working Group P. Pillay-Esnault Internet-Draft Juniper Networks Expires: April 4, 2005 A. Lindem Redback Networks October 4, 2004 OSPFv3 Graceful Restart draft-ietf-ospf-ospfv3-graceful-restart-00.txt Status of this Memo This document is an Internet-Draft and is subject to all provisions of section 3 of RFC 3667. By submitting this Internet-Draft, each author represents that any applicable patent or other IPR claims of which he or she is aware have been or will be disclosed, and any of which he or she become aware will be disclosed, in accordance with RFC 3668. 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. This Internet-Draft will expire on April 4, 2005. Copyright Notice Copyright (C) The Internet Society (2004). Abstract This memo describes the OSPFv3 graceful restart. For OSPFv3, graceful restart is identical to OSPFv2 except for the differences described in this memo. These differences include the format of the grace Link State advertisements (LSA) and other considerations. Pillay-Esnault & Lindem Expires April 4, 2005 [Page 1] Internet-Draft OSPFv3 Graceful Restart October 2004 Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 2. Grace Link State Advertisement . . . . . . . . . . . . . . . . 4 2.1 Grace LSA - LS Type . . . . . . . . . . . . . . . . . . . 4 2.2 Grace LSA Format . . . . . . . . . . . . . . . . . . . . . 5 3. Additional Considerations for OSPFv3 Graceful Restart . . . . 7 3.1 Preservation of LSA ID to Prefix Correspondence . . . . . 7 4. Security Considerations . . . . . . . . . . . . . . . . . . . 8 5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 9 6. Normative References . . . . . . . . . . . . . . . . . . . . . 9 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . 9 A. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 10 Intellectual Property and Copyright Statements . . . . . . . . 11 Pillay-Esnault & Lindem Expires April 4, 2005 [Page 2] Internet-Draft OSPFv3 Graceful Restart October 2004 1. Introduction Graceful OSPF restart [GRACE] describes a mechanism to restart the control plane of an OSPFv2 [OSPFv2] router which still has its forwarding plane intact with a minimum of disruption to the network. In general, the methods described in [GRACE] work for OSPFv3 [OSPFv3] as well. However, OSPFv3 will use a different grace LSA to signal that a router is (or is about) to attempt a graceful restart. This document describes other OSPFv3 differences as well. The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in [RFC2119]. Pillay-Esnault & Lindem Expires April 4, 2005 [Page 3] Internet-Draft OSPFv3 Graceful Restart October 2004 2. Grace Link State Advertisement Grace-LSAs are originated by an OSPFv3 router that wishes to execute a graceful restart of its OSPFv3 software. A grace-LSA requests that the router's neighbors aid in its graceful restart by continuing to advertise the router as fully adjacent during a specified grace period. The grace-LSA contains the restarting router grace-period and the reason code indicate the reason for the graceful restart. In OSPFv3 (refer 2.11 of [OSPFv3]), neighboring routers on a given link are always identified by router ID. This contrasts with the IPv4 behavior where neighbors on point-to-point networks and virtual links are identified by their Router IDs, and neighbors on broadcast, NBMA and Point-to-MultiPoint links are identified by their IPv4 interface addresses. Consequently, there is no requirement for the router-address TLV used for OSPFv3 graceful restart [GRACE]. The grace-LSA body format will remain the same as described in [GRACE]. 2.1 Grace LSA - 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. Pillay-Esnault & Lindem Expires April 4, 2005 [Page 4] Internet-Draft OSPFv3 Graceful Restart October 2004 2.2 Grace LSA Format The format of a grace LSA format is: 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 OSPFv3 is the interface ID of the interface the LSA is originated on. The Length field defines the length of the value portion in octets (thus a TLV with no value portion would have a length of zero). The TLV is padded to four-octet alignment; padding is not included in the length field (so a three octet value would have a length of three, but the total size of the TLV would be eight octets). Nested TLVs are also 32-bit aligned. For example, a one byte value would have the length field set to 1, and three bytes of padding would be added to the end of the value portion of the TLV. Unrecognized types are ignored. Pillay-Esnault & Lindem Expires April 4, 2005 [Page 5] Internet-Draft OSPFv3 Graceful Restart October 2004 The format of each TLV is: 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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Type | Length | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Value... | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 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. 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 state of database synchronization between the router and its neighbors. This TLV must always appear 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 must always appear in a grace-LSA. Pillay-Esnault & Lindem Expires April 4, 2005 [Page 6] Internet-Draft OSPFv3 Graceful Restart October 2004 3. Additional Considerations for OSPFv3 Graceful Restart There are a few OSPFv3 unique considerations in addition to those described in [GRACE]. 3.1 Preservation of LSA ID to Prefix Correspondence In OSPFv2 there is a direct correspondence between type 3 and type 5 LSA IDs and the prefixes being advertised. For OSPFv3, the LSA ID for inter-area prefix LSAs and external LSAs is simply an unsigned 32 bit integer. To avoid network churn during graceful restart, a restarting router SHOULD preserve the LSA ID to prefix correspondence across graceful restarts. Pillay-Esnault & Lindem Expires April 4, 2005 [Page 7] Internet-Draft OSPFv3 Graceful Restart October 2004 4. Security Considerations This document doesn't raise any new security concerns other than those covered in [OSPFv3] and [GRACE]. Pillay-Esnault & Lindem Expires April 4, 2005 [Page 8] Internet-Draft OSPFv3 Graceful Restart October 2004 5. IANA Considerations A new LSA function code will be required for the OSPFv3 grace LSA. Assignment of 0x000b has been suggested herein. Grace LSA TLVs and sub-TLVs will share the same IANA registry as the TLVs and sub-TLVs used by the OSPFv2 grace opaque LSA 6 Normative References [GRACE] Moy, J., Pillay-Esnault, P. and A. Lindem, "Graceful OSPF Restart", RFC 3623, November 2003. [OSPF-TE] Katz, D., Yeung, D. and K. Kompella, "Traffic Engineering Extensions to OSPF", RFC 3630, Septemberx 2003. [OSPFv2] Moy, J., "OSPF Version 2", RFC 2328, April 1998. [OSPFv3] Moy, J., Ferguson, D. and R. Colton, "OSPF for IPv6", RFC 2740, December 1999. [RFC2119] Bradner, S., "Key words for use in RFC's to Indicate Requirement Levels", RFC 2328, March 1977. Authors' Addresses Padma Pillay-Esnault Juniper Networks 1194 N. Mathilda Avenue Sunnyvale, CA 94089 USA EMail: padma@juniper.net Acee Lindem Redback Networks 102 Carric Bend Court Cary, NC 27519 USA EMail: acee@redback.com Pillay-Esnault & Lindem Expires April 4, 2005 [Page 9] Internet-Draft OSPFv3 Graceful Restart October 2004 Appendix A. Acknowledgments Many thanks to Kireeti Kompella with whom much of this was discussed. The authors also wish to thank Kunihiro Ishiguro for his comments. The RFC text was produced using Marshall Rose's xml2rfc tool. Pillay-Esnault & Lindem Expires April 4, 2005 [Page 10] Internet-Draft OSPFv3 Graceful Restart October 2004 Intellectual Property Statement 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. 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Acknowledgment Funding for the RFC Editor function is currently provided by the Internet Society. Pillay-Esnault & Lindem Expires April 4, 2005 [Page 11]