SR Policies Extensions for Headend Behavior in BGP-LS
draft-lin-idr-bgpls-sr-policy-headend-behavior-00
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| Document | Type | Active Internet-Draft (individual) | |
|---|---|---|---|
| Author | Changwang Lin | ||
| Last updated | 2024-09-11 | ||
| RFC stream | (None) | ||
| Intended RFC status | (None) | ||
| Formats | |||
| Stream | Stream state | (No stream defined) | |
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draft-lin-idr-bgpls-sr-policy-headend-behavior-00
IDR Working Group C. Lin
Internet Draft New H3C Technologies
Intended status: Standards Track September 11, 2024
Expires: March 10, 2025
SR Policies Extensions for Headend Behavior in BGP-LS
draft-lin-idr-bgpls-sr-policy-headend-behavior-00
Abstract
The SRv6 Policy Headend Behaviors are defined in [RFC8986].
This document defines extensions for carrying Headend Behavior when
delivering SR Policies using Border Gateway Protocol Link-State
(BGP-LS).
Status of this Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
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This Internet-Draft will expire on March 10, 2025.
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document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal
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Internet-Draft SR Policy Headend Behavior in BGP-LS September 2024
Section 4.e of the Trust Legal Provisions and are provided without
warranty as described in the Simplified BSD License.
Table of Contents
1. Introduction...................................................3
1.1. Requirements Language.....................................3
2. Carrying Headend Behavior in BGP-LS............................3
2.1. Headend Behavior TLV......................................3
2.2. L2 Headend Behavior TLV...................................4
3. Security Considerations........................................6
4. IANA Considerations............................................6
5. References.....................................................6
5.1. Normative References......................................6
Authors' Addresses................................................7
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1. Introduction
Segment Routing (SR) [RFC8402] is a source routing paradigm that
explicitly indicates the forwarding path for packets at the ingress
node. The ingress node steers packets into a specific path according
to the Segment Routing Policy (SR Policy) as defined in [RFC9256].
[RFC8986] describes a set of SRv6 Policy Headend [RFC8402]
behaviors, primarily including H.Encaps, H.Encaps.Red, H.Encaps.L2,
and H.Encaps.L2.Red.
[I-D. lin-idr-sr-policy-headend-behavior] defines extensions to BGP
SR policy, enabling the distribution of SR policies that carry
headend behavior. This allows the headend to be instructed to
perform specific behaviors when packets are steered into the SR
policy.
[I-D.ietf-idr-bgp-ls-sr-policy] describes a mechanism for
distributing SR policy information to external components using BGP-
LS. This information can be used by external components for tasks
such as path computation, re-optimization, service placement, and
network visualization.
This document defines two new TLVs that enable the headend to report
the headend behaviors associated with the SR Policy CP by using BGP-
LS.
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. Carrying Headend Behavior in BGP-LS
2.1. Headend Behavior TLV
A SR Policy CP may be instantiated with a specific headend behavior
via a local configuration, PCEP, or BGP SR Policy signaling. Then
the state and attributes of the headend behavior associated with the
candidate path of SR policy can be distributed to the controller.
This TLV is carried in the optional non-transitive BGP Attribute
"LINK_STATE Attribute" defined in [RFC9552] associated with the SR
Policy CP NLRI type.
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This TLV is optional and only one these TLVs is advertised for a
given SR Policy CP. If multiple TLVs are present, then the first one
is considered valid and the rest are ignored as describe in [I-
D.ietf-idr-bgp-ls-sr-policy].
The Headend Behavior sub-TLV encodes the default headend behavior
associated with the candidate path for L3 traffic. When the headend
steers L3 packets into that SR Policy and the associated candidate
path is active, the specific headend behavior should be performed by
default.
The TLV has the following format:
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 2
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Headend Behavior | RESERVED |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
where:
o Type: to be assigned by IANA.
o Length: 2 octets. The total length of the value field not
including Type and Length fields
o Headend Behavior: a 2-octet value. The following values are
defined.
* TBD: H.Encaps. A headend behavior defined in [RFC8986].
* TBD: H.Encaps.Red. A headend behavior defined in [RFC8986].
o RESERVED: 2 octets of reserved bits. SHOULD be set to zero on
transmission and MUST be ignored on receipt.
2.2. L2 Headend Behavior TLV
A SR Policy CP may be instantiated with a specific L2 Headend
behavior via a local configuration, PCEP, or BGP SR Policy
signaling. Then the state and attributes of the L2 Headend behavior
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associated with the candidate path of SR policy can be distributed
to the controller.
This TLV is carried in the optional non-transitive BGP Attribute
"LINK_STATE Attribute" defined in [RFC9552] associated with the SR
Policy CP NLRI type.
This TLV is optional and only one these TLVs is advertised for a
given SR Policy CP. If multiple TLVs are present, then the first one
is considered valid and the rest are ignored as describe in [I-
D.ietf-idr-bgp-ls-sr-policy].
The L2 Headend Behavior sub-TLV encodes the default headend behavior
associated with the candidate path for L2 traffic. When the headend
steers L2 packets into that SR Policy and the associated candidate
path is active, the specific L2 headend behavior should be performed
by default.
The TLV has the following format:
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 2
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| l2 Headend Behavior | RESERVED |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
where:
o Type: to be assigned by IANA.
o Length: 2 octets. The total length of the value field not
including Type and Length fields
o L2 Headend Behavior: a 2-octet value. The following values are
defined.
* TBD: H.Encaps.L2. A headend behavior defined in [RFC8986].
* TBD: H.Encaps.L2.Red. A headend behavior defined in [RFC8986].
o RESERVED: 2 octets of reserved bits. SHOULD be set to zero on
transmission and MUST be ignored on receipt.
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3. 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.
Security considerations for acquiring and distributing BGP-LS
information are discussed in [RFC9552].
4. IANA Considerations
IANA maintains a registry group called "Border Gateway Protocol -
Link State (BGP-LS) Parameters" with a registry called "BGP-LS NLRI
and Attribute TLVs". The following TLV codepoints are suggested for
early allocation by IANA):
Codepoint Description Reference
----------------------------------------------------------
TBD Headend Behavior This document
TBD L2 Headend Behavior This document
5. References
5.1. Normative References
[I-D.lin-idr-sr-policy-headend-behavior] Lin, C., Jiang, W., Liu, Y.
Chen, M., and Chen, R., "BGP Extensions of SR Policy for
Headend Behavior", Work in Progress, Internet-Draft,
draft-lin-idr-sr-policy-headend-behavior, 16 May 2024,
<https://www.ietf.org/archive/id/draft-lin-idr-sr-policy-
headend-behavior-04.txt>.
[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>.
[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>.
[RFC8402] Filsfils, C., Ed., Previdi, S., Ed., Ginsberg, L.,
Decraene, B., Litkowski, S., and R. Shakir, "Segment
Routing Architecture", RFC 8402, DOI 10.17487/RFC8402,
July 2018, <https://www.rfc-editor.org/info/rfc8402>.
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[RFC8986] Filsfils, C., Ed., Camarillo, P., Ed., Leddy, J., Voyer,
D., Matsushima, S., and Z. Li, "Segment Routing over IPv6
(SRv6) Network Programming", RFC 8986,DOI
10.17487/RFC8986, February 2021,<https://www.rfc-
editor.org/info/rfc8986>.
[RFC9256] Filsfils, C., Talaulikar, K., Ed., Voyer, D., Bogdanov,
A., and P. Mattes, "Segment Routing Policy Architecture",
RFC 9256, DOI 10.17487/RFC9256, July 2022,
<https://www.rfc-editor.org/info/rfc9256>.
Authors' Addresses
Changwang Lin
New H3C Technologies
China
Email: linchangwang.04414@h3c.com
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