Inter-Domain Routing R. Chen
Internet-Draft D. Zhao
Intended status: Standards Track ZTE Corporation
Expires: 2 September 2024 K. Talaulikar
Cisco Systems, Inc.
Y. Liu
China Mobile
L. Changwang
New H3C Technologies
1 March 2024
Validity of SR Policy Candidate Path
draft-chen-idr-bgp-sr-policy-cp-validity-02
Abstract
This document defines extensions to BGP to distribute the validity
control parameters of a candidate path for an SR Policy.
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document authors. All rights reserved.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
1.1. Requirements Language . . . . . . . . . . . . . . . . . . 2
2. Carrying CP Validity Sub-TLV in BGP . . . . . . . . . . . . . 3
3. CP Validity Sub-TLV . . . . . . . . . . . . . . . . . . . . . 3
4. Operations . . . . . . . . . . . . . . . . . . . . . . . . . 4
5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 4
6. Security Considerations . . . . . . . . . . . . . . . . . . . 5
7. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 5
8. Normative References . . . . . . . . . . . . . . . . . . . . 5
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 6
1. Introduction
SR Policy architecture are specified in [RFC9256]. An SR Policy
comprises one or more candidate paths (CP) of which at a given time
one and only one may be active (i.e., installed in forwarding and
usable for steering of traffic). Each CP in turn may have one or
more SID-List of which one or more may be active; when multiple SID-
List are active then traffic is load balanced over them.
[I-D.chen-spring-sr-policy-cp-validity]supplemented candidate path
validity criterion in [RFC9256]. It defines three validity control
parameters under candidate Path to control the validity judgment of
candidate Path.
This document defines extensions to BGP to distribute the validity
control parameters of a candidate path for an SR Policy.
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.
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2. Carrying CP Validity Sub-TLV in BGP
As defined in [I-D.ietf-idr-segment-routing-te-policy], a new SAFI is
defined (the SR Policy SAFI with codepoint 73) as well as a new NLRI.
The NLRI contains the SR Policy candidate path and, according to
[I-D.ietf-idr-segment-routing-te-policy], the content of the SR
Policy Candidate Path is encoded in the Tunnel Encapsulation
Attribute defined in [RFC9012] using a new Tunnel-Type called SR
Policy Type with codepoint 15. This document defines CP Validity
Sub-TLV to carry the validity control parameters of a candidate path.
The new SR Policy encoding structure with CP Validity Sub-TLV is
expressed as below:
SR Policy SAFI NLRI: <Distinguisher, Policy-Color, Endpoint>
Attributes:
Tunnel Encaps Attribute (23)
Tunnel Type: SR Policy (15)
Binding SID
SRv6 Binding SID
Preference
Priority
Policy Name
Policy Candidate Path Name
Explicit NULL Label Policy (ENLP)
CP Validity Sub-TLV
Segment List
Weight
Segment
Segment
...
...
Figure 1
3. CP Validity Sub-TLV
The format of the CP Validity Sub-TLV is defined as follows:
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 | valid SL count| Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| valid SL weight |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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Figure 2
where:
Type: to be assigned by IANA.
Length: the total length of the value field not including Type and
Length fields.
valid SL count：1-octet field which indicates the minimum number of
valid segment Lists under the active candidate path. When the number
of valid segment Lists under candidate path is greater than or equal
to this field, the candidate path is considered valid. 0 indicates no
requirement for SL count. 0xff indicates that the candidate path is
considered valid only if all the segment Lists are valid.
valid SL weight: 4-octet field which indicates the minimum value of
the sum of the weights of the valid segment List under the active
candidate Path. When the sum of the weights of the valid segment
Lists under the candidate path is greater than or equal to this
field, the candidate Path is considered valid. 0 indicates no
requirement for weight.0xffffffff indicates that the candidate path
is considered valid only if all the segment Lists are valid.
4. Operations
The document does not bring new operation beyond the description of
operations defined in [I-D.ietf-idr-segment-routing-te-policy]. The
existing operations defined in
[I-D.ietf-idr-segment-routing-te-policy] can apply to this document
directly.
Typically, but not limit to, the SR policies carrying the validity
control parameters of the candidate path are configured by a
controller.
After configuration, the SR policies carrying the validity control
parameters of the candidate path will be advertised by BGP update
messages. The operation of advertisement is the same as defined in
[I-D.ietf-idr-segment-routing-te-policy], as well as the reception.
5. IANA Considerations
This document defines a new sub-TLV in the registry "BGP Tunnel
Encapsulation Attribute sub-TLVs" to be assigned by IANA:
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Value Description Reference
------- ------------------------- --------------
TBD CP Validity Sub-TLV This document
Figure 3
6. Security Considerations
Procedures and protocol extensions defined in this document do not
affect the security considerations discussed in
[I-D.ietf-idr-segment-routing-te-policy].
7. Acknowledgements
TBD.
8. Normative References
[I-D.chen-spring-sr-policy-cp-validity]
Chen, R., Zhao, D., and C. Lin, "Validity of SR Policy
Candidate Path", Work in Progress, Internet-Draft, draft-
chen-spring-sr-policy-cp-validity-01, 19 October 2023,
<https://datatracker.ietf.org/doc/html/draft-chen-spring-
sr-policy-cp-validity-01>.
[I-D.ietf-idr-segment-routing-te-policy]
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-segment-
routing-te-policy-26, 23 October 2023,
<https://datatracker.ietf.org/doc/html/draft-ietf-idr-
segment-routing-te-policy-26>.
[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>.
[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>.
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Authors' Addresses
Ran Chen
ZTE Corporation
Nanjing
China
Email: chen.ran@zte.com.cn
Detao Zhao
ZTE Corporation
Nanjing
China
Email: zhao.detao@zte.com.cn
Ketan Talaulikar
Cisco Systems, Inc.
Email: ketant.ietf@gmail.com
Yisong Liu
China Mobile
Beijing
China
Email: liuyisong@chinamobile.com
Changwang Lin
New H3C Technologies
Beijing
China
Email: linchangwang.04414@h3c.com
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