Internet DRAFT - draft-ietf-idr-bgp-ls-isis-flood-reflection
draft-ietf-idr-bgp-ls-isis-flood-reflection
Inter-Domain Routing J. Head, Ed.
Internet-Draft T. Przygienda
Intended status: Experimental Juniper Networks
Expires: 12 August 2024 9 February 2024
BGP-LS Extensions for IS-IS Flood Reflection
draft-ietf-idr-bgp-ls-isis-flood-reflection-04
Abstract
IS-IS Flood Reflection is a mechanism that allows flat, single-area
IS-IS topologies to scale beyond their traditional limitations.
This document defines new BGP-LS (BGP Link-State) TLVs in order to
carry IS-IS Flood Reflection information.
Status of This Memo
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This Internet-Draft will expire on 12 August 2024.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
1.1. Requirements Language . . . . . . . . . . . . . . . . . . 2
2. BGP-LS Extensions for IS-IS Flood Reflection . . . . . . . . 2
2.1. IS-IS Flood Reflection TLV . . . . . . . . . . . . . . . 3
3. Design Considerations . . . . . . . . . . . . . . . . . . . . 3
4. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 4
4.1. Requested TLV Entries . . . . . . . . . . . . . . . . . . 4
5. Security Considerations . . . . . . . . . . . . . . . . . . . 4
6. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 5
7. References . . . . . . . . . . . . . . . . . . . . . . . . . 5
7.1. Normative References . . . . . . . . . . . . . . . . . . 5
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 6
1. Introduction
IS-IS Flood Reflection [RFC9377] is a mechanism that allows flat,
single-area IS-IS topologies to scale beyond their existing
limitations.
Flood Reflection topologies are broken into clusters. The
participating nodes must convey their unique Cluster ID signifying
their membership in a particular topology as well as their role (e.g.
Flood Reflector or Client).
BGP Link-State RFC9552 [RFC9552] defines mechanisms to advertise
information about the underlying IGP in BGP NLRI to an external
entity (e.g. a controller). A new BGP-LS TLV is required in order to
describe IS-IS Flood Reflection node and link details. This document
defines that TLV.
1.1. Requirements Language
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.
2. BGP-LS Extensions for IS-IS Flood Reflection
Controllers may need to compute traffic engineered paths across Flood
Reflection clusters. This requires that they be aware of Flood
Reflection information (be it operational or configured), such as
Cluster ID, C-bit (which indicates Flood Reflector or Client), and
any applicable sub-TLVs.
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The IS-IS Flood Reflection TLV can be advertised in BGP-LS as either
a Node attribute or a Link attribute. When describing a node, values
are derived from the IS-IS Flood Reflection Discovery Sub-TLV. When
describing a link, values are derived from the IS-IS Adjacency Sub-
TLV. The semantics of any fields within the TLV/sub-TLVs are
described in [RFC9377].
This document defines the following BGP-LS TLVs for use with IS-IS
Flood Reflection.
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 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|C| RESERVED |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Flood Reflection Cluster ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Sub-TLVs ... |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 1: IS-IS Flood Reflection TLV
2.1. IS-IS Flood Reflection TLV
This section defines a BGP-LS Attribute that corresponds to IS-IS
Flood Reflection TLVs/sub-TLVs as described in [RFC9377]
where:
*Type:* 1160
*Length:* variable
3. Design Considerations
It is typical that a BGP-LS extension mirror all of the corresponding
IGP components (i.e. TLVs, sub-TLVs, and sub-sub-TLVs) in order to
carry the necessary IGP information. IS-IS Flood Reflection
[RFC9377] describes "Tunnel-Based" deployments where an optional
"Flood Reflection Discovery Tunnel Type Sub-Sub-TLV" is used to
facilitate the creation of "L1 Shortcuts" (i.e. tunnels) between
nodes in a Flood Reflection cluster. In this document, it is
RECOMMENDED that this sub-sub-TLV be excluded from the BGP-LS
extension for the following reasons.
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For example, shortcuts could be point-to-point IS-IS tunnels or be
encapsulated by other means. In deployments where the tunnels are
IS-IS based, no additional BGP-LS extension is required as the
existing BGP-LS extensions for IS-IS will suffice.
However, for deployments where tunnels are encapsulated by other
means it is not desirable for BGP-LS to carry that information as it
is tunnel information and not IGP information. Other existing or new
BGP-LS extensions that correspond to the particular tunnel type
SHOULD be used to fulfill any BGP-LS requirements.
An implementation MAY still choose to include the "Flood Reflection
Discovery Tunnel Type Sub-Sub-TLV" for the sake of completeness. For
example, it might be beneficial for cases where BGP-LS is the only
way this information can be obtained.
4. IANA Considerations
This section requests the following values from the "BGP-LS Node
Descriptor, Link Descriptor, Prefix Descriptor, and Attribute TLVs"
registry for the following TLVs:
4.1. Requested TLV Entries
+=======+=============+================================+===========+
| TLV | Description | IS-IS TLV/Sub-TLV | Reference |
| Code | | | |
| Point | | | |
+=======+=============+================================+===========+
| 1160 | IS-IS Flood | (22|23|25|141|222|223|242)/161 | This |
| | Reflection | | document. |
+-------+-------------+--------------------------------+-----------+
Table 1: Requested TLV Entries
5. Security Considerations
Procedures and protocol extensions defined in this document do not
affect the BGP security model. See the "Security Considerations"
section of [RFC4271] for a discussion of BGP security. Also, refer
to [RFC4272] and [RFC6952] for analyses of BGP security issues.
Security considerations for acquiring and distributing BGP-LS
information are discussed in [RFC9552].
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The TLVs introduced in this document are used to propagate IS-IS
Flood Reflection TLVs defined in [RFC9377]. These TLVs represent IS-
IS Flood Reflection state and are therefore assumed to support any/
all of the required security and authentication mechanisms as
described in [RFC9377] to prevent any security issues when
propagating the TLVs into BGP-LS.
6. Acknowledgements
The authors would like to thank Ketan Talaulikar for several
iterations of review and practical suggestions.
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>.
[RFC4271] Rekhter, Y., Li, T., and S. Hares, "A Border Gateway
Protocol 4 (BGP-4)", January 2006,
<https://www.rfc-editor.org/info/rfc4271>.
[RFC4272] Murphy, S., "BGP Security Vulnerabilities Analysis",
January 2006, <https://www.rfc-editor.org/info/rfc4272>.
[RFC6952] Jethanandani, M., Patel, K., and L. Zheng, "Analysis of
BGP, LDP, PCEP, and MSDP Issues According to the Keying
and Authentication for Routing Protocols (KARP) Design
Guide", May 2013,
<https://www.rfc-editor.org/info/rfc6952>.
[RFC8126] Cotton, M., Leiba, B., and T. Narten, "Guidelines for
Writing an IANA Considerations Section in RFCs", June
2017, <https://www.rfc-editor.org/info/rfc8126>.
[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>.
[RFC9377] Przygienda, T., Ed., Bowers, C., Lee, Y., Sharma, A., and
R. White, "IS-IS Flood Reflection", RFC 9377,
DOI 10.17487/RFC9377, April 2023,
<https://www.rfc-editor.org/info/rfc9377>.
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[RFC9552] Talaulikar, K., "Distribution of Link-State and Traffic
Engineering Information Using BGP", January 2024,
<https://www.rfc-editor.org/info/rfc9552>.
Authors' Addresses
Jordan Head (editor)
Juniper Networks
1137 Innovation Way
Sunnyvale, CA
United States of America
Email: jhead@juniper.net
Tony Przygienda
Juniper Networks
1137 Innovation Way
Sunnyvale, CA
United States of America
Email: prz@juniper.net
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