draft-ietf-lsr-isis-flood-reflection-00.txt   draft-ietf-lsr-isis-flood-reflection-01.txt 
Network Working Group A. Przygienda Network Working Group A. Przygienda
Internet-Draft C. Bowers Internet-Draft C. Bowers
Intended status: Standards Track Juniper Intended status: Standards Track Juniper
Expires: January 7, 2021 Y. Lee Expires: January 28, 2021 Y. Lee
A. Sharma A. Sharma
Comcast Comcast
R. White R. White
Juniper Juniper
July 6, 2020 July 27, 2020
IS-IS Flood Reflection IS-IS Flood Reflection
draft-ietf-lsr-isis-flood-reflection-00 draft-ietf-lsr-isis-flood-reflection-01
Abstract Abstract
This document describes an optional ISIS extension that allows the This document describes an optional ISIS extension that allows the
creation of IS-IS flood reflection topologies. Flood reflection creation of IS-IS flood reflection topologies. Flood reflection
allows the creation of topologies where L1 areas provide transit allows the creation of topologies where L1 areas provide transit
forwarding for L2 destinations within an L2 topology. It forwarding for L2 destinations within an L2 topology. It
accomplishes this by creating L2 flood reflection adjacencies within accomplishes this by creating L2 flood reflection adjacencies within
each L1 area. The L2 flood reflection adjacencies are used to flood each L1 area. The L2 flood reflection adjacencies are used to flood
L2 LSPDUs, and they are used in the L2 SPF computation. However, L2 LSPDUs, and they are used in the L2 SPF computation. However,
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Internet-Drafts are working documents of the Internet Engineering Internet-Drafts are working documents of the Internet Engineering
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This Internet-Draft will expire on January 7, 2021. This Internet-Draft will expire on January 28, 2021.
Copyright Notice Copyright Notice
Copyright (c) 2020 IETF Trust and the persons identified as the Copyright (c) 2020 IETF Trust and the persons identified as the
document authors. All rights reserved. document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents Provisions Relating to IETF Documents
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publication of this document. Please review these documents publication of this document. Please review these documents
carefully, as they describe your rights and restrictions with respect carefully, as they describe your rights and restrictions with respect
to this document. Code Components extracted from this document must to this document. Code Components extracted from this document must
include Simplified BSD License text as described in Section 4.e of include Simplified BSD License text as described in Section 4.e of
the Trust Legal Provisions and are provided without warranty as the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License. described in the Simplified BSD License.
Table of Contents Table of Contents
1. Description . . . . . . . . . . . . . . . . . . . . . . . . . 2 1. Description . . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Further Details . . . . . . . . . . . . . . . . . . . . . . . 8 2. Further Details . . . . . . . . . . . . . . . . . . . . . . . 8
3. Flood Reflection TLV . . . . . . . . . . . . . . . . . . . . 8 3. Flood Reflection TLV . . . . . . . . . . . . . . . . . . . . 9
4. Flood Reflection Discovery Sub-TLV . . . . . . . . . . . . . 10 4. Flood Reflection Discovery Sub-TLV . . . . . . . . . . . . . 10
5. Flood Reflection Adjacency Sub-TLV . . . . . . . . . . . . . 10 5. Flood Reflection Adjacency Sub-TLV . . . . . . . . . . . . . 11
6. Flood Reflection Discovery . . . . . . . . . . . . . . . . . 11 6. Flood Reflection Discovery . . . . . . . . . . . . . . . . . 11
7. Flood Reflection Adjacency Formation . . . . . . . . . . . . 12 7. Flood Reflection Adjacency Formation . . . . . . . . . . . . 12
8. Redistribution of Prefixes . . . . . . . . . . . . . . . . . 12 8. Redistribution of Prefixes . . . . . . . . . . . . . . . . . 13
9. Route Computation . . . . . . . . . . . . . . . . . . . . . . 13 9. Route Computation . . . . . . . . . . . . . . . . . . . . . . 13
10. Special Considerations . . . . . . . . . . . . . . . . . . . 13 10. Special Considerations . . . . . . . . . . . . . . . . . . . 14
11. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 14 11. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 14
11.1. New IS-IS TLV Codepoint . . . . . . . . . . . . . . . . 14 11.1. New IS-IS TLV Codepoint . . . . . . . . . . . . . . . . 14
11.2. Sub TLVs for TLV 242 . . . . . . . . . . . . . . . . . . 14 11.2. Sub TLVs for TLV 242 . . . . . . . . . . . . . . . . . . 15
11.3. Sub TLVs for TLV 22, 23, 25, 141, 222, and 223 . . . . . 15 11.3. Sub TLVs for TLV 22, 23, 25, 141, 222, and 223 . . . . . 15
12. Security Considerations . . . . . . . . . . . . . . . . . . . 15 12. Security Considerations . . . . . . . . . . . . . . . . . . . 15
13. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 15 13. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 15
14. References . . . . . . . . . . . . . . . . . . . . . . . . . 15 14. References . . . . . . . . . . . . . . . . . . . . . . . . . 15
14.1. Informative References . . . . . . . . . . . . . . . . . 15 14.1. Informative References . . . . . . . . . . . . . . . . . 15
14.2. Normative References . . . . . . . . . . . . . . . . . . 15 14.2. Normative References . . . . . . . . . . . . . . . . . . 16
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 16 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 16
1. Description 1. Description
Due to the inherent properties of link-state protocols the number of Due to the inherent properties of link-state protocols the number of
IS-IS routers within a flooding domain is limited by processing and IS-IS routers within a flooding domain is limited by processing and
flooding overhead on each node. While that number can be maximized flooding overhead on each node. While that number can be maximized
by well written implementations and techniques such as exponential by well written implementations and techniques such as exponential
back-offs, IS-IS will still reach a saturation point where no further back-offs, IS-IS will still reach a saturation point where no further
routers can be added to a single flooding domain. In some L2 routers can be added to a single flooding domain. In some L2
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distance wise. distance wise.
Another possible variation is for an implementation to approximate Another possible variation is for an implementation to approximate
with the L1 tunnel cost the cost of the underlying topology. with the L1 tunnel cost the cost of the underlying topology.
Redundancy can be achieved by building multiple flood reflectors in Redundancy can be achieved by building multiple flood reflectors in
the L1 area. Multiple flood reflectors do not need any the L1 area. Multiple flood reflectors do not need any
synchronization mechanisms amongst themselves, except standard ISIS synchronization mechanisms amongst themselves, except standard ISIS
flooding and database maintenance procedures. flooding and database maintenance procedures.
On change in either flood reflection role or cluster ID on IIH the
adjacency has to be reset.
3. Flood Reflection TLV 3. Flood Reflection TLV
The Flood Reflection TLV is a new top-level TLV that MAY appear in The Flood Reflection TLV is a new top-level TLV that MAY appear in
IIHs. The Flood Reflection TLV indicates the flood reflector cluster IIHs. The Flood Reflection TLV indicates the flood reflector cluster
(based on Flood Reflection Cluster ID) that a given router is (based on Flood Reflection Cluster ID) that a given router is
configured to participate in. It also indicates whether the router configured to participate in. It also indicates whether the router
is configured to play the role of either flood reflector or flood is configured to play the role of either flood reflector or flood
reflector client. The Flood Reflection Cluster ID and flood reflector client. The Flood Reflection Cluster ID and flood
reflector roles advertised in the IIHs are used to ensure that flood reflector roles advertised in the IIHs are used to ensure that flood
reflector adjacencies are only formed between a flood reflector and reflector adjacencies are only formed between a flood reflector and
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Sub-TLVs. Sub-TLVs.
11.1. New IS-IS TLV Codepoint 11.1. New IS-IS TLV Codepoint
This document requests the following IS-IS TLV: This document requests the following IS-IS TLV:
Value Name IIH LSP SNP Purge Value Name IIH LSP SNP Purge
----- --------------------------------- --- --- --- ----- ----- --------------------------------- --- --- --- -----
TBD1 Flood Reflection y n n n TBD1 Flood Reflection y n n n
Suggested value for TBD1 is 161.
11.2. Sub TLVs for TLV 242 11.2. Sub TLVs for TLV 242
This document request the following registration in the "sub-TLVs for This document request the following registration in the "sub-TLVs for
TLV 242" registry. TLV 242" registry.
Type Description Type Description
---- ----------- ---- -----------
TBD2 Flood Reflection Discovery TBD2 Flood Reflection Discovery
Suggested value for TBD2 is 161.
11.3. Sub TLVs for TLV 22, 23, 25, 141, 222, and 223 11.3. Sub TLVs for TLV 22, 23, 25, 141, 222, and 223
This document requests the following registration in the "sub-TLVs This document requests the following registration in the "sub-TLVs
for TLV 22, 23, 25, 141, 222, and 223" registry. for TLV 22, 23, 25, 141, 222, and 223" registry.
Type Description 22 23 25 141 222 223 Type Description 22 23 25 141 222 223
---- -------------------------------- --- --- --- --- --- --- ---- -------------------------------- --- --- --- --- --- ---
TBD3 Flood Reflector Adjacency y y y(s) y y y TBD3 Flood Reflector Adjacency y y n y y y
Suggested value for TBD3 is 161.
12. Security Considerations 12. Security Considerations
This document introduces no new security concerns to ISIS or other This document introduces no new security concerns to ISIS or other
specifications referenced in this document. specifications referenced in this document.
13. Acknowledgements 13. Acknowledgements
The authors thank Shraddha Hegde, Peter Psenak, and Les Ginsberg for The authors thank Shraddha Hegde, Peter Psenak, and Les Ginsberg for
their thorough review and detailed discussions. their thorough review and detailed discussions.
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