IDR C. Lin Internet Draft New H3C Technologies Intended status: Standards Track J. Li Expires: March 8, 2025 China Mobile September 8, 2024 BGP SR Policy Extensions for Administrative Flags draft-lin-idr-sr-policy-admin-flags-00 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. Internet-Drafts are working documents of the Internet Engineering Task Force (IETF), its areas, and its working groups. Note that other groups may also distribute working documents as Internet- Drafts. Internet-Drafts are draft documents valid for a maximum of six months and may be updated, replaced, or obsoleted by other documents at any time. It is inappropriate to use Internet-Drafts as reference material or to cite them other than as "work in progress." The list of current Internet-Drafts can be accessed at http://www.ietf.org/ietf/1id-abstracts.txt The list of Internet-Draft Shadow Directories can be accessed at http://www.ietf.org/shadow.html This Internet-Draft will expire on March 8, 2025. Lin, et al. Expires March 3, 2025 [Page 1] Internet-Draft BGP SR Policy Administrative Flags 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 (http://trustee.ietf.org/license-info) in effect on the date of publication of this document. 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 Simplified BSD License text as described in Section 4.e of the Trust Legal Provisions and are provided without warranty as described in the Simplified BSD License. Table of Contents 1. Introduction...................................................3 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........................................6 4. IANA Considerations............................................7 5. References.....................................................7 5.1. Normative References......................................7 5.2. Informative References....................................7 Authors' Addresses................................................8 Lin, et al. Expires March 8, 2025 [Page 2] Internet-Draft BGP SR Policy Administrative Flags September 2024 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, [I-D.ietf-idr-sr- policy-safi] 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 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 CP as "Ignore service routes Prefix SID" can help optimize the segment list. Additionally, Flag control can determine whether the SR Policy is intended as a transit SR Policy. For more details, see section 8.3 of [RFC9256]. 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 [I-D.ietf-idr-sr-policy-safi], the SR policy encoding structure is as follows: Lin, et al. Expires March 8, 2025 [Page 3] Internet-Draft BGP SR Policy Administrative Flags September 2024 SR Policy SAFI NLRI: 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: 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. Lin, et al. Expires March 8, 2025 [Page 4] Internet-Draft BGP SR Policy Administrative Flags September 2024 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: TBD. 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|T| | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 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. - T-Flag: Indicates the CP has been marked as ineligible for use as Transit Policy on the headend when set. Refer to section 8.3 of [RFC9256]. Lin, et al. Expires March 8, 2025 [Page 5] Internet-Draft BGP SR Policy Administrative Flags September 2024 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: TBD. 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| | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Figure 6: Administrative Flags where: - S-Flag: Indicates the CP is in an administrative shut state when set. 3. Security Considerations The security requirements and mechanisms described in [I-D.ietf-idr- sr-policy-safi] also apply to this document. This document does not introduce any new security consideration. Lin, et al. Expires March 8, 2025 [Page 6] Internet-Draft BGP SR Policy Administrative Flags September 2024 4. IANA Considerations This document defines a new Sub-TLV in the registry "SR Policy Segment List AdminState Sub-TLVs" [I-D.ietf-idr-sr-policy-safi]: 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. [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, . [I-D.ietf-idr-sr-policy-safi] 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-sr-policy-safi-06, 30 July 2024, . 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, . Lin, et al. Expires March 8, 2025 [Page 7] Internet-Draft BGP SR Policy Administrative Flags September 2024 Authors' Addresses Changwang Lin New H3C Technologies China Email: linchangwang.04414@h3c.com Jinming Li China Mobile 32 Xuanwumen West Street Beijing Xicheng District, 100053 China Email: lijinming@chinamobile.com Lin, et al. Expires March 8, 2025 [Page 8]