Validity of SR Policy Candidate Path
draft-chen-idr-bgp-sr-policy-cp-validity-00
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draft-chen-idr-bgp-sr-policy-cp-validity-00
Inter-Domain Routing R. Chen
Internet-Draft D. Zhao
Intended status: Standards Track ZTE Corporation
Expires: 5 January 2024 4 July 2023
Validity of SR Policy Candidate Path
draft-chen-idr-bgp-sr-policy-cp-validity-00
Abstract
[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.
Status of This Memo
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This Internet-Draft will expire on 8 January 2024.
Copyright Notice
Copyright (c) 2023 IETF Trust and the persons identified as the
document authors. All rights reserved.
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Internet-Draft Validity of SR Policy Candidate Path July 2023
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Please review these documents carefully, as they describe your rights
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Requirements Language . . . . . . . . . . . . . . . . . . . . 2
3. Carrying CP Validity Sub-TLV in BGP . . . . . . . . . . . . . 3
4. CP Validity Sub-TLV . . . . . . . . . . . . . . . . . . . . . 3
5. Operations . . . . . . . . . . . . . . . . . . . . . . . . . 4
6. This document defines a new sub-TLV in the registry "BGP Tunnel
Encapsulation Attribute sub-TLVs" to be assigned by
IANA: . . . . . . . . . . . . . . . . . . . . . . . . . . 5
7. Security Considerations . . . . . . . . . . . . . . . . . . . 5
8. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 5
9. 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.
2. Requirements Language
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in RFC 2119 [RFC2119].
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3. 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
4. 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 qty |valid SL weight|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| valid SL weight ratio |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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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 quantity：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 quantity. 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.
valid SL weight ratio: 1-octet field which indicates the minimum
proportion WTV/WTA. WTV: The sum weights of the valid segment list
under the active CP. WTA: The sum weights of all the segment lists
under the active CP. When WTV/WTA is greater than or equal to this
field, the candidate Path is considered valid. 0 indicates no
requirement on weight proportion.100 indicates that the candidate
path is considered valid only if all the segment lists are valid.
5. 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.
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6. This document defines a new sub-TLV in the registry "BGP Tunnel
Encapsulation Attribute sub-TLVs" to be assigned by IANA:
Value Description Reference
------- ------------------------- --------------
TBD CP Validity Sub-TLV This document
Figure 3
7. 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].
8. Acknowledgements
TBD.
9. 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-00, 5 July 2023,
<https://datatracker.ietf.org/api/v1/doc/document/draft-
chen-spring-sr-policy-cp-validity/>.
[I-D.ietf-idr-segment-routing-te-policy]
Previdi, S., Filsfils, C., Talaulikar, K., Mattes, P.,
Jain, D., and S. Lin, "Advertising Segment Routing
Policies in BGP", Work in Progress, Internet-Draft, draft-
ietf-idr-segment-routing-te-policy-20, 27 July 2022,
<https://datatracker.ietf.org/doc/html/draft-ietf-idr-
segment-routing-te-policy-20>.
[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>.
[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
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