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-04
Abstract
This document defines extensions to Border Gateway Protocol (BGP) to
distribute SR policies carrying headend behavior.
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Table of Contents
1. 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
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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.
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:
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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)
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.
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o RESERVED: 2 octets of reserved bits. SHOULD be set to zero on
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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3. Security Considerations
Procedures 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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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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