IDR Working Group C. Lin
Internet Draft New H3C Technologies
Intended status: Standards Track W. Jiang
Expires: November 12, 2024 Y. Liu
China Mobile
M. Chen
New H3C Technologies
R. Chen
ZTE Corporation
May 16, 2024
BGP Extensions of SR Policy for Headend Behavior draft-lin-idr-sr-policy-headend-behavior-04Abstract
This document defines extensions to Border Gateway Protocol (BGP) to distribute SR policies carrying headend behavior.
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Table of Contents1. Introduction...................................................2
1.1. Requirements Language.....................................3
2. Headend Behavior in SR Policy..................................3
2.1. Headend Behavior Sub-TLV..................................4
2.2. L2 Headend Behavior Sub-TLV...............................5
3. Security Considerations........................................6
4. IANA Considerations............................................6
5. References.....................................................6
5.1. Normative References......................................6
5.2. Informative References....................................7
Authors' Addresses................................................7
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]. In order to distribute SR policies to the headend, [I-D.ietf-idr-sr- policy-safi] specifies a mechanism by using BGP.As described in [RFC9256], a headend can steer a packet flow into an SR Policy in various ways, including BSID steering, per-destination steering, per-flow steering, and policy-based steering. Moreover, [I-D.ietf-idr-ts-flowspec-srv6-policy] describes a way by using BGP FlowSpec to steer packets into an SRv6 Policy.
[RFC8986] defines End.B6.Encaps behavior and End.B6.Encaps.Red behavior for SRv6 BSID. When receiving packets with an active SID matching a local BSID of these kinds, the headend will perform corresponding behaviors. Different BSID behaviors are suitable for different scenarios. For example, comparing with End.B6.Encaps, End.B6.Encaps.Red reduces the size of the SRH by excluding the first SID, which can be useful for the devices with lower capacity of SID depths, like the switches in data center network.
The SRv6 Binding SID sub-TLV is defined in [I-D.ietf-idr-sr-policy- safi] to signal the SRv6 BSID information along with SR Policies. It enables the specified SRv6 BSID behavior to be instantiated on the headend node. However, if the packets are steering into an SR Policy in some other way than using BSID, the headend behavior is not specified during the distributing of SR Policy by BGP. The network operator has to use additional tools, like NETCONF, to signal the headend behavior.
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This document defines extensions to Border Gateway Protocol (BGP) to distribute SR policies carrying headend behavior. So that the headend can be instructed to perform specific behavior when packets are steered into the SR policy without BSID.
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. Headend Behavior in SR Policy
As defined in [I-D.ietf-idr-sr-policy-safi], the SR policy encoding structure is as follows:SR Policy SAFI NLRI: <Distinguisher, Policy-Color, Endpoint>
Attributes:
Tunnel Encaps Attribute (23)
Tunnel Type: SR Policy
Binding SID SRv6 Binding SID Preference Priority Policy Name Policy Candidate Path Name Explicit NULL Label Policy (ENLP) Segment List
Weight
Segment Segment ...
...
SR policy with headend behavior is expressed as follows: SR Policy SAFI NLRI: <Distinguisher, Policy-Color, Endpoint>
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Attributes:Tunnel Encaps Attribute (23)
Tunnel Type: SR Policy
Binding SID SRv6 Binding SID Preference Priority Policy Name Policy Candidate Path Name Explicit NULL Label Policy (ENLP) Headend Behavior L2 Headend Behavior Segment List
Weight
Segment Segment ...
...
2.1. Headend Behavior Sub-TLV
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. In the case of BSID steering, the behavior defined by the BSID overrides the default headend behavior.The Headend Behavior sub-TLV is optional, and MUST NOT appear more than once in the SR Policy encoding.
The Headend Behavior sub-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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type | Length | RESERVED |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Headend Behavior |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
where:o Type: to be assigned by IANA.
o Length: 4. o RESERVED: 2 octets of reserved bits. SHOULD be set to zero on
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transmission and MUST be ignored on receipt.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].
2.2. L2 Headend Behavior Sub-TLV
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 headend behavior should be performed by default.The L2 Headend Behavior sub-TLV is optional, and MUST NOT appear more than once in the SR Policy encoding.
The L2 Headend Behavior sub-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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type | Length | RESERVED |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| L2 Headend Behavior |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
where:o Type: to be assigned by IANA.
o Length: 4.
o RESERVED: 2 octets of reserved bits. SHOULD be set to zero on
transmission and MUST be ignored on receipt.
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].
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Internet-Draft BGP SR Policy Headend Behavior May 2024 3. Security ConsiderationsProcedures and protocol extensions defined in this document do not affect the security considerations discussed in [I-D.ietf-idr-sr- policy-safi].
4. IANA Considerations
Headend Behavior Sub-TLV (TBD)L2 Headend Behavior Sub-TLV (TBD)
5. References 5.1. 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>.
[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>.
[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>.
[I-D.ietf-idr-sr-policy-safi] Previdi, S., Filsfils, C., Talaulikar,
K., Mattes, P., and D. Jain, "Advertising Segment Routing Policies in BGP", Work in Progress, Internet-Draft, draft- ietf-idr-sr-policy-safi-01, 4 March 2024, <https://datatracker.ietf.org/api/v1/doc/document/draft- ietf-idr-sr-policy-safi/>.
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Internet-Draft BGP SR Policy Headend Behavior May 2024 5.2. Informative References[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>.
[I-D.ietf-idr-ts-flowspec-srv6-policy] Jiang, W., Liu, Y., Zhuang,
S., Mishra, G., and S. Chen, "Traffic Steering using BGP Flowspec with SR Policy", Work in Progress, Internet- Draft, draft-ietf-idr-ts-flowspec-srv6-policy-03, 17 June 2023, <http://www.ietf.org/internet-drafts/draft-ietf-idr- ts-flowspec-srv6-policy-03.txt>.
Authors' Addresses
Changwang Lin New H3C Technologies China Email: linchangwang.04414@h3c.com
Wenying Jiang China Mobile China Email: jiangwenying@chinamobile.com
Yisong Liu China Mobile China Email: liuyisong@chinamobile.com
Mengxiao Chen New H3C Technologies China Email: chen.mengxiao@h3c.com
Ran Chen ZTE Corporation China Email: chen.ran@zte.com.cn
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