Internet DRAFT - draft-lp-idr-bgp-ls-sr-policy-supplement
draft-lp-idr-bgp-ls-sr-policy-supplement
IDR Working Group Y. Liu
Internet-Draft S. Peng
Intended status: Standards Track ZTE
Expires: 10 September 2023 9 March 2023
Supplement of BGP-LS Distribution for SR Policies and State
draft-lp-idr-bgp-ls-sr-policy-supplement-00
Abstract
This document supplements some additional information of the segment
list in the BGP-LS advertisement for SR Policy state information .
Status of This Memo
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This Internet-Draft will expire on 10 September 2023.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
1.1. Requirements Language . . . . . . . . . . . . . . . . . . 3
2. BGP-LS Extensions for Distributing Segment List States . . . 3
3. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 3
4. Security Considerations . . . . . . . . . . . . . . . . . . . 3
5. References . . . . . . . . . . . . . . . . . . . . . . . . . 3
5.1. Normative References . . . . . . . . . . . . . . . . . . 4
5.2. Informative References . . . . . . . . . . . . . . . . . 4
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 4
1. Introduction
SR Policy architecture details 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. Each CP in turn may have one or
more SID-List of which one or more may be active; when multiple are
active then traffic is load balanced over them.
[I-D.ietf-pce-multipath] proposes extensions to PCEP to specify the
protection relationship among segment lists within the candidate
path. There would be segment lists in the CP acting as backup for
one or more primary segment lists, the backup lists only carry
rerouted traffic after the protected path fails.
[I-D.ietf-idr-bgp-ls-sr-policy] describes a mechanism to collect the
SR policy information that is locally available in a node and
advertise it into BGP Link State (BGP-LS) updates. Various TLVs are
defined to enable the headend to report the state at the SR Policy CP
level. For example, there's a B Flag in the SR Candidate Path State
TLV indicating the CP is in an administrative shut state when set.
Currently, a few segment list-related information is not included in
[I-D.ietf-idr-bgp-ls-sr-policy]. One is the information to indicate
that the segment list is a backup path as described in
[I-D.ietf-pce-multipath]. And the segment list may be shut by the
administrator, this information may also needed and reported via BGP-
LS.
This document supplements some additional information of the segment
list in the BGP-LS advertisement for SR Policy state information .
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1.1. 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 [RFC2119] [RFC8174]
when, and only when, they appear in all capitals, as shown here.
2. BGP-LS Extensions for Distributing Segment List States
SR Segment List TLV is defined in [I-D.ietf-idr-bgp-ls-sr-policy] to
to report the SID-List(s) of a candidate path.As show in
Figure 1,this document introduces two new flags in the flag field of
SR Segment List TLV, where,
0 1
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|D|E|C|V|R|F|A|T|M|S|B| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 1: Flag Field of SR Segment List TLV
* S-Flag: Indicates the segment list is in administrative shut state
when set.
* B-Flag: Indicates the segment list is a backup path described in
[I-D.ietf-pce-multipath] when set, otherwise it is the primary
path.
3. IANA Considerations
This document requests bit 9 and bit 10 in the flag field of "SR
Segment List TLV" [I-D.ietf-idr-bgp-ls-sr-policy] under the "BGP-LS
Node Descriptor, Link Descriptor, Prefix Descriptor, and Attribute
TLVs" registry.
Bit Description Reference
------------------------------------------------------------------
9 Administrative Shut State Flag(S-Flag) This document
10 Backup Path State Flag(B-Flag) This document
4. Security Considerations
Procedures and protocol extensions defined in this document do not
affect the security considerations discussed in
[I-D.ietf-idr-bgp-ls-sr-policy].
5. References
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5.1. Normative References
[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-00, 9 March 2023,
<https://datatracker.ietf.org/doc/html/draft-ietf-idr-bgp-
ls-sr-policy-00>.
[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>.
5.2. Informative References
[I-D.ietf-pce-multipath]
Koldychev, M., Sivabalan, S., Saad, T., Beeram, V. P.,
Bidgoli, H., Yadav, B., Peng, S., and G. S. Mishra, "PCEP
Extensions for Signaling Multipath Information", Work in
Progress, Internet-Draft, draft-ietf-pce-multipath-07, 14
November 2022, <https://datatracker.ietf.org/doc/html/
draft-ietf-pce-multipath-07>.
[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>.
Authors' Addresses
Yao Liu
ZTE
Nanjing
China
Email: liu.yao71@zte.com.cn
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Shaofu Peng
ZTE
Nanjing
China
Email: peng.shaofu@zte.com.cn
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