Internet DRAFT - draft-basavaraj-lsr-ospf-gr-enhancements
draft-basavaraj-lsr-ospf-gr-enhancements
LSR Working Group S. Boutros
Internet-Draft A. Dubey
Intended status: Standards Track V. Basavaraj
Expires: 29 May 2024 VMware
A. Lindem
LabN Consulting, L.L.C.
26 November 2023
OSPF Graceful Restart Enhancements
draft-basavaraj-lsr-ospf-gr-enhancements-08
Abstract
This document describes enhancements to the OSPF graceful restart
procedures to improve routing convergence in some OSPF network
deployments. This document updates RFC 3623 and RFC 5187.
Status of This Memo
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This Internet-Draft will expire on 29 May 2024.
Copyright Notice
Copyright (c) 2023 IETF Trust and the persons identified as the
document authors. All rights reserved.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Conventions used in this document . . . . . . . . . . . . . . 2
3. Graceful Restart Enhancements . . . . . . . . . . . . . . . . 2
3.1. Stub-Link Network Scenarios . . . . . . . . . . . . . . . 2
3.2. Multiple Failure Scenarios . . . . . . . . . . . . . . . 3
4. Security Considerations . . . . . . . . . . . . . . . . . . . 3
5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 3
6. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 3
7. References . . . . . . . . . . . . . . . . . . . . . . . . . 3
7.1. Normative References . . . . . . . . . . . . . . . . . . 3
7.2. Informative References . . . . . . . . . . . . . . . . . 4
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 4
1. Introduction
This document describes the enhancements to the current OSPF
[RFC2328] and OSPFv3 [RFC5340] graceful restart procedures as
respectively defined in OSPF Graceful Restart [RFC3623] and OSPFv3
Graceful Restart [RFC5187] to improve routing convergence in certain
OSPF network deployment scenarios. The goal is for both the
restarting OSPF node and the helper OSPF node to terminate the OSPF
graceful restart procedure faster and not wait for the grace period
expiry in those network scenarios and hence improve the overall OSPF
network convergence.
2. Conventions used in this document
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
"OPTIONAL" in this document are to be interpreted as described in BCP
14 [RFC2119] [RFC8174] when, and only when, they appear in all
capitals, as shown here.
3. Graceful Restart Enhancements
3.1. Stub-Link Network Scenarios
+--------+ +--------+ +--------+
|Router-1|---Area 0----|Router-2|---Area 1---|Router-3|
+------=-+ +--------+ +--------+
Figure 1: OSPF topology with Graceful Restart
As graphically depicted in figure 1, Router-2 is an area border
router (ABR) with OSPF links in 2 areas. Furthermore, Router-2 has
formed full adjacencies only in Area 0. In Area 1, Router-2 has an
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OSPF link enabled but Router2 could not form an adjacency either
because Router-3 is down or Router-3 does not have OSPF enabled.
Hence, Router-2 will only have a stub link in Area 1.
On restart, the ABR router Router-2, having only a stub link in the
Area 1, will never receive its pre-restart LSA in this area and will
never form an adjacency and will have to wait for the grace period
expiry leading to slower OSPF routing convergence.
For this scenario, if no OSPF control packets are received within the
dead interval on a link in Area 1 as per the above network scenario,
Router-2 MUST mark the link as stub and MUST not wait for the grace
period to form an adjacency on this link to successfully Exit GR.
3.2. Multiple Failure Scenarios
In scenarios where more than one router is restarting at the same
time in the same OSPF area and StrictLSAChecking is disabled,
restarting OSPF routers will end up waiting the entire grace interval
to exit GR. If the restarting routers receive a Grace Link State
Advertisement (LSA) from another router in a given area after
restart, and the helper routers receive grace LSAs from more than one
router, this will indicate that there have been multiple failures.
Therefore, the helper and restarting routers MUST terminate GR and
avoid any unnecessary delay in OSPF routing convergence.
4. Security Considerations
The security considerations in OSPF Graceful Restart [RFC3623] and
OSPFv3 Graceful Restart [RFC5187] are applicable. This document does
not introduce any additional security considerations.
5. IANA Considerations
This specification doesn not require any IANA assignments.
6. Acknowledgements
TBD
7. References
7.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997,
<https://www.rfc-editor.org/info/rfc2119>.
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[RFC3623] Moy, J., Pillay-Esnault, P., and A. Lindem, "Graceful OSPF
Restart", RFC 3623, DOI 10.17487/RFC3623, November 2003,
<https://www.rfc-editor.org/info/rfc3623>.
[RFC5187] Pillay-Esnault, P. and A. Lindem, "OSPFv3 Graceful
Restart", RFC 5187, DOI 10.17487/RFC5187, June 2008,
<https://www.rfc-editor.org/info/rfc5187>.
[RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
May 2017, <https://www.rfc-editor.org/info/rfc8174>.
7.2. Informative References
[RFC2328] Moy, J., "OSPF Version 2", STD 54, RFC 2328,
DOI 10.17487/RFC2328, April 1998,
<https://www.rfc-editor.org/info/rfc2328>.
[RFC5340] Coltun, R., Ferguson, D., Moy, J., and A. Lindem, "OSPF
for IPv6", RFC 5340, DOI 10.17487/RFC5340, July 2008,
<https://www.rfc-editor.org/info/rfc5340>.
Authors' Addresses
Sami Boutros
VMware
Email: sboutros@vmware.com
Ankur Dubey
VMware
Email: adubey@vmware.com
Vijayalaxmi Basavaraj
VMware
Email: vbasavaraj@vmware.com
Acee Lindem
LabN Consulting, L.L.C.
301 Midenhall Way
Cary, NC 27513
United States of America
Email: acee.ietf@gmail.com
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