Advertisement of Candidate Path Validity Control Parameters using BGP-LS
draft-chen-idr-bgp-ls-sr-policy-cp-validity-01
| Document | Type | Active Internet-Draft (individual) | |
|---|---|---|---|
| Authors | Ran Chen , Detao Zhao , Ketan Talaulikar , Yisong Liu , Changwang Lin | ||
| Last updated | 2024-03-01 | ||
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draft-chen-idr-bgp-ls-sr-policy-cp-validity-01
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
Advertisement of Candidate Path Validity Control Parameters using BGP-LS
draft-chen-idr-bgp-ls-sr-policy-cp-validity-01
Abstract
This document describes a mechanism to collect the configuration and
states of SR policies carrying the validity control parameters of the
candidate path by using BGP Link-State (BGP-LS) updates. Such
information can be used by external components for path computation,
re-optimization, service placement, etc.
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 2 September 2024.
Copyright Notice
Copyright (c) 2024 IETF Trust and the persons identified as the
document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents (https://trustee.ietf.org/
license-info) in effect on the date of publication of this document.
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Please review these documents carefully, as they describe your rights
and restrictions with respect to this document. Code Components
extracted from this document must include Revised BSD License text as
described in Section 4.e of the Trust Legal Provisions and are
provided without warranty as described in the Revised BSD License.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
1.1. Requirements Language . . . . . . . . . . . . . . . . . . 3
2. Carrying CP Validity Sub-TLV in BGP-LS . . . . . . . . . . . 3
3. CP Validity Sub-TLV . . . . . . . . . . . . . . . . . . . . . 3
4. Operations . . . . . . . . . . . . . . . . . . . . . . . . . 4
5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 4
6. Security Considerations . . . . . . . . . . . . . . . . . . . 4
7. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 4
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.
In many network scenarios, the configuration and state of each TE
Policy is required by a controller which allows the network operator
to optimize several functions and operations through the use of a
controller aware of both topology and state information
[I-D.ietf-idr-te-lsp-distribution].
Based on the mechanism defined in [I-D.ietf-idr-te-lsp-distribution],
this document defines extensions to BGP-LS to distribute the validity
control parameters of a candidate path for an SR Policy.
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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 CP Validity Sub-TLV in BGP-LS
In order to collect configuration and states of SR policies carrying
the validity control parameters of the candidate path, this document
defines a new SR Policy state TLV which enable the headend to report
the validity control parameters of a candidate path.
This TLV is carried in the optional non-transitive BGP Attribute
"LINK_STATE Attribute" defined in [RFC7752] associated with the SR
Policy CP NLRI type.
This TLV is optional and only one this TLV is advertised for a given
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].
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 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 1
where:
Type: to be assigned by IANA.
Length: the total length of the value field not including Type and
Length fields.
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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 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.
4. Operations
The operations procedures of [RFC7752] can apply to this document.
Typically, but not limit to, the SR policies carrying the validity
control parameters of the candidate path can be distributed by the
ingress node.
5. IANA Considerations
IANA maintains a registry called "Border Gateway Protocol - Link
State (BGP-LS) Parameters" with a sub-registry called "Node Anchor,
Link Descriptor and Link Attribute TLVs". The following TLV
codepoints are suggested (for early allocation by IANA):
Value Description Reference
------- ------------------------- --------------
TBD CP Validity Sub-TLV This document
Figure 2
6. 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 [RFC7752].
7. Acknowledgements
TBD.
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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-bgp-ls-sr-policy]
Previdi, S., Talaulikar, K., Dong, J., Gredler, H., and J.
Tantsura, "Advertisement of Segment Routing Policies using
BGP Link-State", Work in Progress, Internet-Draft, draft-
ietf-idr-bgp-ls-sr-policy-03, 5 November 2023,
<https://datatracker.ietf.org/doc/html/draft-ietf-idr-bgp-
ls-sr-policy-03>.
[I-D.ietf-idr-te-lsp-distribution]
Previdi, S., Talaulikar, K., Dong, J., Chen, M., Gredler,
H., and J. Tantsura, "Distribution of Traffic Engineering
(TE) Policies and State using BGP-LS", Work in Progress,
Internet-Draft, draft-ietf-idr-te-lsp-distribution-19, 24
January 2023, <https://datatracker.ietf.org/doc/html/
draft-ietf-idr-te-lsp-distribution-19>.
[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>.
[RFC4271] Rekhter, Y., Ed., Li, T., Ed., and S. Hares, Ed., "A
Border Gateway Protocol 4 (BGP-4)", RFC 4271,
DOI 10.17487/RFC4271, January 2006,
<https://www.rfc-editor.org/info/rfc4271>.
[RFC7752] Gredler, H., Ed., Medved, J., Previdi, S., Farrel, A., and
S. Ray, "North-Bound Distribution of Link-State and
Traffic Engineering (TE) Information Using BGP", RFC 7752,
DOI 10.17487/RFC7752, March 2016,
<https://www.rfc-editor.org/info/rfc7752>.
[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>.
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[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
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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