BGP SR Policy Extensions for Administrative Flags
draft-lin-idr-sr-policy-admin-flags-05
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| Document | Type | Active Internet-Draft (candidate for idr WG) | |
|---|---|---|---|
| Authors | Changwang Lin , Yisong Liu , Ran Chen , Amal Karboubi | ||
| Last updated | 2026-06-23 (Latest revision 2026-06-03) | ||
| RFC stream | Internet Engineering Task Force (IETF) | ||
| Intended RFC status | (None) | ||
| Formats | |||
| Additional resources | Mailing list discussion | ||
| Stream | WG state | Call For Adoption By WG Issued | |
| Document shepherd | (None) | ||
| IESG | IESG state | I-D Exists | |
| Consensus boilerplate | Unknown | ||
| Telechat date | (None) | ||
| Responsible AD | (None) | ||
| Send notices to | (None) |
draft-lin-idr-sr-policy-admin-flags-05
IDR C. Lin
Internet Draft New H3C Technologies
Intended status: Standards Track Y. Liu
Expires: December 06, 2026 China Mobile
Ran.Chen
ZTE
A. Karboubi
Ciena
June 04, 2026
BGP SR Policy Extensions for Administrative Flags
draft-lin-idr-sr-policy-admin-flags-05
Abstract
Segment Routing is a source routing paradigm that explicitly
indicates the forwarding path for packets at the ingress node. An SR
Policy is a set of candidate paths, each consisting of one or more
segment lists.
This document defines an extension to the BGP SR Policy that sets
the administrative state of the candidate path or segment list,
facilitating the operation and maintenance of the SR Policy.
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 December 06, 2026.
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Copyright Notice
Copyright (c) 2026 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
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Table of Contents
1. Introduction...................................................2
1.1. Requirements Language.....................................3
2. Admin State in SR Policy.......................................3
2.1. Candidate Path Administrative Flags Sub-TLV...............5
2.2. Segment List Administrative Flags Sub-TLV.................6
3. Security Considerations........................................7
4. IANA Considerations............................................7
5. References.....................................................7
5.1. Normative References......................................7
5.2. Informative References....................................8
Appendix A. Cross WG Information..................................9
A.1. Link to Spring WG.........................................9
A.2. Interaction with PCE WG...................................9
A.3. Interaction with SRV6ops Recommendations..................9
Authors' Addresses...............................................10
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, [RFC9830]
specifies a mechanism by using BGP.
For management purposes, the controller may occasionally need to
temporarily divert traffic from a specific forwarding path and then
restore it later. In such cases, the controller can issue an
Administrative Down command to a specific path in the SR Policy on
the device without removing the path. When it is time to restore the
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path, the controller can simply issue an Administrative Up command
to that same path.
In another scenario, such as in 6PE or EPE situations where it is
necessary to conserve service route SIDs, the SR Policy Flag can be
extended to indicate settings. For example, configuring the
Candidate Path as "Ignore service routes Prefix SID" can help
optimize the segment list.
In some scenarios, the Candidate Path cannot be used as a backup
path. The operator needs to control the Candidate Path status to
identify whether this CP can serve as a backup path.
In [RFC9256], section 8.2 defines the Drop-Upon-Invalid behavior. An
SR Policy MAY be enabled for the Drop-Upon-Invalid behavior.
Currently, there is no behavior control for Drop-Upon-Invalid on the
path of an SR policy.
This document defines an extension to the BGP SR Policy that sets
the management state of the candidate path or the segment list,
facilitating the operation and maintenance of the 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.
2. Admin State in SR Policy
As defined in [RFC9830], the SR policy encoding structure is 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)
Segment List
Weight
Segment
Segment
...
...
SR policy with Administrative Flags are expressed as below:
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
Policy Candidate Path Administrative Flags
Explicit NULL Label Policy (ENLP)
Segment List
Weight
Segment List Administrative Flags
Segment
Segment
...
...
The Candidate Path Administrative Flags can also be advertised using
the Candidate Path Administrative Flags sub-TLV, as defined in
Section 2.1.
The segment list Administrative Flags can be advertised using the
Segment List Administrative Flags sub-TLV, as defined in Section
2.2.
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2.1. Candidate Path Administrative Flags Sub-TLV
The Candidate Path Administrative Flags sub-TLV is used to indicate
the AdminState of the Candidate Path.
The Candidate Path Administrative Flags sub-TLV is optional and it
MUST NOT appear more than once inside the Segment List sub-TLV.
The Candidate Path Administrative Flags 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 2
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type | Length | Flags |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
where:
o Type: TBD1.
o Length: 2.
o Flags: 2 octet of flags.
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
|S |B |I |D |E | Reserved |
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
Figure 5: Administrative Flags
where:
- S-Flag: Indicates the CP is in an administrative shut state
when set.
- B-Flag: Indicates the CP is configured as "backup
ineligible".
- I-Flag: Indicates the CP is configured as "Ignore service
route's Prefix SID". It allows traffic to a BGP service route
to be steered over an SR policy without imposing the service
route's prefix label or SRv6 Service SID.
- D-Flag: Indicates the CP has been marked as the "Drop Upon
Invalid" behavior as described in section 8.2 of [RFC9256].
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- E-Flag: Indicates that the CP is set to 'candidate path
eligible' as defined in [I-D. ietf-spring-sr-policy-
eligibility. If set, it indicates that the eligibility
attribute of the candidate path is true. If not set, it
indicates that the eligibility attribute of the candidate
path is false.
- Reserved: The unassigned bits in the Flags field MUST be set
to zero upon transmission and MUST be ignored upon receipt.
2.2. Segment List Administrative Flags Sub-TLV
The Segment List Administrative Flags sub-TLV is used to indicate
the AdminState of the Segment List of Candidate Path.
The Segment List Administrative Flags sub-TLV is optional and it
MUST NOT appear more than once inside the Segment List sub-TLV.
The Segment List Administrative Flags 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 2
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type | Length | Flags |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
where:
o Type: TBD2.
o Length: 2.
o Flags: 2 octet of flags.
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|S|E| Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 6: Administrative Flags
where:
- S-Flag: Indicates the Segment List is in an administrative
shut state when set.
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- E-Flag: When set, indicates the Segment List is in an eligible
state (capable of forwarding traffic).
When cleared, indicates the Segment List is ineligible
(cannot forward traffic).
- Reserved: The unassigned bits in the Flags field MUST be set
to zero upon transmission and MUST be ignored upon receipt.
3. Security Considerations
The security considerations of BGP [RFC4271] and BGP SR policy
[RFC9830] apply to this document.
The Candidate Path Administrative Flags sub-TLV is used to indicate
the AdminState of the Candidate Path. The Segment List
Administrative Flags sub-TLV is used to indicate the AdminState of
the Segment List of the Candidate Path. The values of these two sub-
TLVs affect the state of the Candidate Path or Segment List in the
SR Policy, which may consequently impact packet forwarding in the
network. Therefore, when configuring, querying, and reporting
control plane Candidate Path Administrative Flags and Segment List
Administrative Flags in BGP, care must be taken to protect this
mission critical or commercially sensitive information.
4. IANA Considerations
This document defines a new Sub-TLV in the registry "SR Policy
Segment List AdminState Sub-TLVs" [RFC9830]:
Value Description Reference
-------------------------------------------------------
TBD1 Candidate Path Administrative Flags sub-TLV This
document
TBD2 Segment List Administrative Flags sub-TLV This
document
5. References
5.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[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>.
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[RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
2119 Key Words", BCP 14, RFC 8174, May 2017
[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>.
[RFC9830] Previdi, S., Filsfils, C., Talaulikar, K., Mattes, P., and
D. Jain, "Advertising Segment Routing Policies in BGP",
RFC 9830, DOI 10.17487/RFC9830, September 2025,
<https://www.rfc-editor.org/info/rfc9830>.
[I-D. ietf-spring-sr-policy-eligibility] Karboubi, A., Shah, H.,
Sivalaban, S., Stone, A. and Schmutz, C., "Eligibility
Concept in Segment Routing Policies", draft-ietf-spring-
sr-policy-eligibility-00 (work in progress), January 2026.
5.2. Informative References
[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. draft-karboubi-spring-sidlist-optimized-cs-sr] Karboubi, A.,
Alaettinoglu, C., Shah, H., Sivabalan, S., Defillipi, T.,
and Maheshwari, P., "Circuit Style Segment Routing
Policies with Optimized SID List Depth", Work in Progress,
Internet-Draft, draft-karboubi-spring-sidlist-optimized-
cs-sr-03, 2 June 2025,
<https://datatracker.ietf.org/doc/html/draft-karboubi-
spring-sidlist- -cs-sr-03>.
[I-D. draft-ietf-srv6ops-srv6-deployment] McBride, M., Liu, Y., Li,
Z., Durmus, M., Erdogan, E., Mishra, G., and Horn, J.,
"SRv6 Deployment Options", Work in Progress, Internet-
Draft, draft-ietf-srv6ops-srv6-deployment, 25 February
2026,<https://datatracker.ietf.org/doc/html/draft-ietf-
srv6ops-srv6-deployment-02>.
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Appendix A. Cross WG Information
This section describes cross-working group information for use
during the IETF review process. This section will be removed by the
RFC editor prior to publication.
A.1. Link to Spring WG
This document implements the features defined in Section 4 of [I-D.
ietf-spring-sr-policy-eligibility] and Section 8.2 of [RFC9256] via
BGP. This spring features require this document to be implemented.
A.2. Interaction with PCE WG
The BGP extension defined by this document also may be implemented
by a new TLV of PCEP according to Section 4.3 of [I-D. draft-
karboubi-spring-sidlist-optimized-cs-sr].
A.3. Interaction with SRV6ops Recommendations
This optimization feature could be distributed to external
components using BGP-LS extension defined in [I-D. draft-lin-idr-
bgp-ls-sr-policy-admin-flag].
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Authors' Addresses
Changwang Lin
New H3C Technologies
China
Email: linchangwang.04414@h3c.com
Yisong Liu
China Mobile
32 Xuanwumen West Street
Beijing
Xicheng District, 100053
China
Email: liuyisong@chinamobile.com
Ran Chen
ZTE Corporation
Email: chen.ran@zte.com.cn
Amal Karboubi
Ciena
Email: akarboub@ciena.com
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