draft-ietf-isis-reverse-metric-15.txt   draft-ietf-isis-reverse-metric-16.txt 
Networking Working Group N. Shen Networking Working Group N. Shen
Internet-Draft Cisco Systems Internet-Draft Cisco Systems
Intended status: Standards Track S. Amante Intended status: Standards Track S. Amante
Expires: April 19, 2019 Apple, Inc. Expires: May 8, 2019 Apple, Inc.
M. Abrahamsson M. Abrahamsson
T-Systems Nordic T-Systems Nordic
October 16, 2018 November 4, 2018
IS-IS Routing with Reverse Metric IS-IS Routing with Reverse Metric
draft-ietf-isis-reverse-metric-15 draft-ietf-isis-reverse-metric-16
Abstract Abstract
This document describes a mechanism to allow IS-IS routing to quickly This document describes a mechanism to allow IS-IS routing to quickly
and accurately shift traffic away from either a point-to-point or and accurately shift traffic away from either a point-to-point or
multi-access LAN interface during network maintenance or other multi-access LAN interface during network maintenance or other
operational events. This is accomplished by signaling adjacent IS-IS operational events. This is accomplished by signaling adjacent IS-IS
neighbors with a higher reverse metric, i.e., the metric towards the neighbors with a higher reverse metric, i.e., the metric towards the
signaling IS-IS router. signaling IS-IS router.
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This Internet-Draft will expire on April 19, 2019. This Internet-Draft will expire on May 8, 2019.
Copyright Notice Copyright Notice
Copyright (c) 2018 IETF Trust and the persons identified as the Copyright (c) 2018 IETF Trust and the persons identified as the
document authors. All rights reserved. document authors. All rights reserved.
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described in the Simplified BSD License. described in the Simplified BSD License.
Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
1.1. Node and Link Isolation . . . . . . . . . . . . . . . . . 2 1.1. Node and Link Isolation . . . . . . . . . . . . . . . . . 3
1.2. Distributed Forwarding Planes . . . . . . . . . . . . . . 3 1.2. Distributed Forwarding Planes . . . . . . . . . . . . . . 3
1.3. Spine-Leaf Applications . . . . . . . . . . . . . . . . . 3 1.3. Spine-Leaf Applications . . . . . . . . . . . . . . . . . 3
1.4. LDP IGP Synchronization . . . . . . . . . . . . . . . . . 3 1.4. LDP IGP Synchronization . . . . . . . . . . . . . . . . . 3
1.5. IS-IS Reverse Metric . . . . . . . . . . . . . . . . . . 3 1.5. IS-IS Reverse Metric . . . . . . . . . . . . . . . . . . 4
1.6. Specification of Requirements . . . . . . . . . . . . . . 4 1.6. Specification of Requirements . . . . . . . . . . . . . . 4
2. IS-IS Reverse Metric TLV . . . . . . . . . . . . . . . . . . 4 2. IS-IS Reverse Metric TLV . . . . . . . . . . . . . . . . . . 4
3. Elements of Procedure . . . . . . . . . . . . . . . . . . . . 6 3. Elements of Procedure . . . . . . . . . . . . . . . . . . . . 6
3.1. Processing Changes to Default Metric . . . . . . . . . . 6 3.1. Processing Changes to Default Metric . . . . . . . . . . 6
3.2. Multi-Topology IS-IS Support on Point-to-point links . . 7 3.2. Multi-Topology IS-IS Support on Point-to-point links . . 7
3.3. Multi-Access LAN Procedures . . . . . . . . . . . . . . . 7 3.3. Multi-Access LAN Procedures . . . . . . . . . . . . . . . 7
3.4. LDP/IGP Synchronization on LANs . . . . . . . . . . . . . 8 3.4. LDP/IGP Synchronization on LANs . . . . . . . . . . . . . 8
3.5. Operational Guidelines . . . . . . . . . . . . . . . . . 9 3.5. Operational Guidelines . . . . . . . . . . . . . . . . . 9
4. Security Considerations . . . . . . . . . . . . . . . . . . . 9 4. Security Considerations . . . . . . . . . . . . . . . . . . . 10
5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 10 5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 10
6. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 10 6. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 10
7. References . . . . . . . . . . . . . . . . . . . . . . . . . 10 7. References . . . . . . . . . . . . . . . . . . . . . . . . . 11
7.1. Normative References . . . . . . . . . . . . . . . . . . 10 7.1. Normative References . . . . . . . . . . . . . . . . . . 11
7.2. Informative References . . . . . . . . . . . . . . . . . 11 7.2. Informative References . . . . . . . . . . . . . . . . . 11
Appendix A. Node Isolation Challenges . . . . . . . . . . . . . 12 Appendix A. Node Isolation Challenges . . . . . . . . . . . . . 12
Appendix B. Link Isolation Challenges . . . . . . . . . . . . . 13 Appendix B. Link Isolation Challenges . . . . . . . . . . . . . 13
Appendix C. Contributors' Addresses . . . . . . . . . . . . . . 14 Appendix C. Contributors' Addresses . . . . . . . . . . . . . . 14
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 14 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 14
1. Introduction 1. Introduction
The IS-IS [ISO10589] routing protocol has been widely used in The IS-IS [ISO10589] routing protocol has been widely used in
Internet Service Provider IP/MPLS networks. Operational experience Internet Service Provider IP/MPLS networks. Operational experience
with the protocol, combined with ever increasing requirements for with the protocol, combined with ever increasing requirements for
lossless operations have demonstrated some operational issues. This lossless operations have demonstrated some operational issues. This
document describes the issues and a mechanism for mitigating them. document describes the issues and a mechanism for mitigating them.
This document defines the IS-IS "Reverse Metric" mechanism that
allows an IS-IS node to send a "Reverse Metric" TLV through the IS-IS
IIH PDU to the neighbor or pseudo-node to adjust the routing metric
on the inbound direction.
1.1. Node and Link Isolation 1.1. Node and Link Isolation
IS-IS routing mechanism has the overload-bit, which can be used by IS-IS routing mechanism has the overload-bit, which can be used by
operators to perform disruptive maintenance on the router. But in operators to perform disruptive maintenance on the router. But in
many operational maintenance cases, it is not necessary to divert all many operational maintenance cases, it is not necessary to divert all
the traffic away from this node. It is necessary to avoid only a the traffic away from this node. It is necessary to avoid only a
single link during the maintenance. More detailed descriptions of single link during the maintenance. More detailed descriptions of
the challenges can be found in Appendix A and Appendix B of this the challenges can be found in Appendix A and Appendix B of this
document. document.
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metric offset that a neighbor SHOULD add to the existing, configured metric offset that a neighbor SHOULD add to the existing, configured
Default Metric for the IS-IS link [ISO10589]. Refer to "Elements of Default Metric for the IS-IS link [ISO10589]. Refer to "Elements of
Procedure", in Section 3 for details on how an IS-IS router should Procedure", in Section 3 for details on how an IS-IS router should
process the Metric field in a Reverse Metric TLV. process the Metric field in a Reverse Metric TLV.
The Metric field, in the Reverse Metric TLV, is a "reverse offset The Metric field, in the Reverse Metric TLV, is a "reverse offset
metric" that will either be in the range of 0 - 63 when a "narrow" metric" that will either be in the range of 0 - 63 when a "narrow"
IS-IS metric is used (IS Neighbors TLV, Pseudonode LSP) [RFC1195] or IS-IS metric is used (IS Neighbors TLV, Pseudonode LSP) [RFC1195] or
in the range of 0 - (2^24 - 2) when a "wide" Traffic Engineering in the range of 0 - (2^24 - 2) when a "wide" Traffic Engineering
metric value is used, (Extended IS Reachability TLV) [RFC5305] metric value is used, (Extended IS Reachability TLV) [RFC5305]
[RFC5817]. [RFC5817]. As described below, when the U bit is set, the
accumulated value of the wide metric is in the range of 0 - (2^24 -
1), with (2^24 - 1) metric as non-reachable in IS-IS routing. The
IS-IS metric value of (2^24 - 2) serves as the link of last resort.
There are currently only two Flag bits defined. There are currently only two Flag bits defined.
W bit (0x01): The "Whole LAN" bit is only used in the context of W bit (0x01): The "Whole LAN" bit is only used in the context of
multi-access LANs. When a Reverse Metric TLV is transmitted from a multi-access LANs. When a Reverse Metric TLV is transmitted from a
node to the Designated Intermediate System (DIS), if the "Whole LAN" node to the Designated Intermediate System (DIS), if the "Whole LAN"
bit is set (1), then a DIS SHOULD add the received Metric value in bit is set (1), then a DIS SHOULD add the received Metric value in
the Reverse Metric TLV to each node's existing Default Metric in the the Reverse Metric TLV to each node's existing Default Metric in the
Pseudonode LSP. If the "Whole LAN" bit is not set (0), then a DIS Pseudonode LSP. If the "Whole LAN" bit is not set (0), then a DIS
SHOULD add the received Metric value in the Reverse Metric TLV to the SHOULD add the received Metric value in the Reverse Metric TLV to the
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When the link Traffic Engineering metric is raised to (2^24 - 1) When the link Traffic Engineering metric is raised to (2^24 - 1)
[RFC5817], either due to the reverse-metric mechanism or by explicit [RFC5817], either due to the reverse-metric mechanism or by explicit
user configuration, this SHOULD immediately trigger the CSPF re- user configuration, this SHOULD immediately trigger the CSPF re-
calculation to move the Traffic Engineering traffic away from that calculation to move the Traffic Engineering traffic away from that
link. It is RECOMMENDED also that the CSPF does the immediate CSPF link. It is RECOMMENDED also that the CSPF does the immediate CSPF
re-calculation when the Traffic Engineering metric is raised to (2^24 re-calculation when the Traffic Engineering metric is raised to (2^24
- 2) to be the last resort link. - 2) to be the last resort link.
It is RECOMMENDED that implementations provide a capability to It is RECOMMENDED that implementations provide a capability to
disable any changes by Reverse Metric mechanism through neighbor's disable any IS-IS metric changes by Reverse Metric mechanism through
Hello PDUs. It can be to a node's individual interface Default neighbor's Hello PDUs. It can be to a node's individual interface
Metric or Traffic Engineering parameters based upon receiving a Default Metric or Traffic Engineering parameters based upon receiving
properly formatted Reverse Metric TLVs. a properly formatted Reverse Metric TLVs.
If an implementation enables this mechanism by default, it is If an implementation enables this mechanism by default, it is
RECOMMENDED that it be disabled by the operators when not explicitly RECOMMENDED that it be disabled by the operators when not explicitly
using it. using it.
4. Security Considerations 4. Security Considerations
Security concerns for IS-IS are addressed in [ISO10589], [RFC5304], Security concerns for IS-IS are addressed in [ISO10589], [RFC5304],
[RFC5310], and with various deployment and operational security [RFC5310], and with various deployment and operational security
considerations in [RFC7645]. The enhancement in this document makes considerations in [RFC7645]. The enhancement in this document makes
it possible for one IS-IS router to manipulate the IS-IS Default it possible for one IS-IS router to manipulate the IS-IS Default
Metric and, optionally, Traffic Engineering parameters of adjacent Metric and, optionally, Traffic Engineering parameters of adjacent
IS-IS neighbors. Although IS-IS routers within a single Autonomous IS-IS neighbors. Although IS-IS routers within a single Autonomous
System nearly always are under the control of a single administrative System nearly always are under the control of a single administrative
authority, it is highly RECOMMENDED that operators configure authority, it is highly recommended that operators configure
authentication of IS-IS PDUs to mitigate use of the Reverse Metric authentication of IS-IS PDUs to mitigate use of the Reverse Metric
TLV as a potential attack vector. TLV as a potential attack vector.
5. IANA Considerations 5. IANA Considerations
IANA has allocated IS-IS TLV Codepoints of 16 for the Reverse Metric IANA has allocated IS-IS TLV Codepoints of 16 for the Reverse Metric
TLV. This new TLV has the following attributes: IIH = y, LSP = n, TLV. This new TLV has the following attributes: IIH = y, LSP = n,
SNP = n, Purge = n. SNP = n, Purge = n.
This document also introduces a new registry for sub-TLVs of the This document also introduces a new registry for sub-TLVs of the
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18: Traffic Engineering Metric sub-TLV, as specified in this 18: Traffic Engineering Metric sub-TLV, as specified in this
document (Section 2) document (Section 2)
19-255: Unassigned 19-255: Unassigned
6. Acknowledgments 6. Acknowledgments
The authors would like to thank Mike Shand, Dave Katz, Guan Deng, The authors would like to thank Mike Shand, Dave Katz, Guan Deng,
Ilya Varlashkin, Jay Chen, Les Ginsberg, Peter Ashwood-Smith, Uma Ilya Varlashkin, Jay Chen, Les Ginsberg, Peter Ashwood-Smith, Uma
Chunduri, Alexander Okonnikov, Jonathan Harrison, Dave Ward, Himanshu Chunduri, Alexander Okonnikov, Jonathan Harrison, Dave Ward, Himanshu
Shah, Wes George, Danny McPherson, Ed Crabbe, Russ White, Robert Shah, Wes George, Danny McPherson, Ed Crabbe, Russ White, Robert
Raszuk, Tom Petch and Acee Lindem for their comments and Raszuk, Tom Petch, Stewart Bryant and Acee Lindem for their comments
contributions. and contributions.
This document was produced using Marshall Rose's xml2rfc tool. This document was produced using Marshall Rose's xml2rfc tool.
7. References 7. References
7.1. Normative References 7.1. Normative References
[ISO10589] [ISO10589]
ISO, "Intermediate system to Intermediate system routeing ISO, "Intermediate system to Intermediate system routeing
information exchange protocol for use in conjunction with information exchange protocol for use in conjunction with
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[RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
May 2017, <https://www.rfc-editor.org/info/rfc8174>. May 2017, <https://www.rfc-editor.org/info/rfc8174>.
7.2. Informative References 7.2. Informative References
[I-D.shen-isis-spine-leaf-ext] [I-D.shen-isis-spine-leaf-ext]
Shen, N., Ginsberg, L., and S. Thyamagundalu, "IS-IS Shen, N., Ginsberg, L., and S. Thyamagundalu, "IS-IS
Routing for Spine-Leaf Topology", draft-shen-isis-spine- Routing for Spine-Leaf Topology", draft-shen-isis-spine-
leaf-ext-03 (work in progress), March 2017. leaf-ext-07 (work in progress), October 2018.
[RFC5304] Li, T. and R. Atkinson, "IS-IS Cryptographic [RFC5304] Li, T. and R. Atkinson, "IS-IS Cryptographic
Authentication", RFC 5304, DOI 10.17487/RFC5304, October Authentication", RFC 5304, DOI 10.17487/RFC5304, October
2008, <https://www.rfc-editor.org/info/rfc5304>. 2008, <https://www.rfc-editor.org/info/rfc5304>.
[RFC5310] Bhatia, M., Manral, V., Li, T., Atkinson, R., White, R., [RFC5310] Bhatia, M., Manral, V., Li, T., Atkinson, R., White, R.,
and M. Fanto, "IS-IS Generic Cryptographic and M. Fanto, "IS-IS Generic Cryptographic
Authentication", RFC 5310, DOI 10.17487/RFC5310, February Authentication", RFC 5310, DOI 10.17487/RFC5310, February
2009, <https://www.rfc-editor.org/info/rfc5310>. 2009, <https://www.rfc-editor.org/info/rfc5310>.
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