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.
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.
Disclaimer of Validity
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.
Copyright Statement
Copyright (C) The Internet Society (2004). 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.
Acknowledgment
Funding for the RFC Editor function is currently provided by the
Internet Society.
Pillay-Esnault & Lindem Expires April 4, 2005 [Page 11]