Interdomain Routing Working Group C. Li Internet-Draft M. Chen Intended status: Standards Track J. Dong Expires: October 6, 2018 Z. Li Huawei Technologies April 4, 2018 SR Policies for Path Segment and Bi-directional Path in BGP-LS draft-li-idr-bgp-ls-sr-policy-path-segment-00 Abstract This document specifies the way of collecting configuration and states of SR policies carrying path ID and bi-directional path information by using BPG-LS. Such information can be used by external conponents for many use cases such as performance measurement, path re-optimization and end-to-end protection. 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]. 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). Note that other groups may also distribute working documents as Internet-Drafts. The list of current Internet- Drafts is at https://datatracker.ietf.org/drafts/current/. 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." This Internet-Draft will expire on October 6, 2018. Copyright Notice Copyright (c) 2018 IETF Trust and the persons identified as the document authors. All rights reserved. Li, et al. Expires October 6, 2018 [Page 1] Internet-Draft Path ID and Bi-directional Path in BGP-LS April 2018 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. 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 . . . . . . . . . . . . . . . . . . . . . . . . 2 2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3 3. Carrying SR Path Sub-TLVs in BGP-LS . . . . . . . . . . . . . 3 3.1. SR Path ID Sub-TLV . . . . . . . . . . . . . . . . . . . 4 3.2. Sub-TLVs for Bi-directional Path . . . . . . . . . . . . 5 3.2.1. SR Bi-directional Path Sub-TLV . . . . . . . . . . . 5 3.2.2. SR Reverse Path Segment List Sub-TLV . . . . . . . . 5 4. Operations . . . . . . . . . . . . . . . . . . . . . . . . . 6 5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 6 6. Security Considerations . . . . . . . . . . . . . . . . . . . 6 7. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 6 8. Normative References . . . . . . . . . . . . . . . . . . . . 6 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 8 1. Introduction Segment routing (SR) [I-D.ietf-spring-segment-routing] is a source routing paradigm that allows the ingress node steers packets into a specific path according to the Segment Routing Policy [I-D.filsfils-spring-segment-routing-policy]. However, the SR Policies defined in [I-D.filsfils-spring-segment-routing-policy] only supports uni- directional SR paths and there is no path ID in a Segment List to identify an SR path. For identifying an SR path and supporting bi- directional path [I-D.cheng-spring-mpls-path-segment], new policies carrying Path ID and bi-directional path information are defined in [I-D.li-idr-sr-policy-path-segment-distribution], as well as the extensions to BGP to distribute new SR policies. The path ID can be a path segment in SR-MPLS [I-D.cheng-spring-mpls-path-segment] , or a path ID in SRv6 [I-D.li-spring-passive-pm-for-srv6-np], or other IDs that can identify a 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 Li, et al. Expires October 6, 2018 [Page 2] Internet-Draft Path ID and Bi-directional Path in BGP-LS April 2018 controller aware of both topology and state information [I-D.ietf-idr-te-lsp-distribution]. To collect the TE Policy information that is locally available in a router, [I-D.ietf-idr-te-lsp-distribution] describes a new mechanism by using BGP-LS update messages. Based on the mechanism defined in [I-D.ietf-idr-te-lsp-distribution], this document describes a mechanism to distribute configuration and states of the new SR policies defined in [I-D.li-idr-sr-policy-path-segment-distribution] to external components using BGP-LS. 2. Terminology This memo makes use of the terms defined in [I-D.ietf-spring-segment-routing] and [I-D.ietf-idr-te-lsp-distribution]. 3. Carrying SR Path Sub-TLVs in BGP-LS A mechanism to collect states of SR Policies via BGP-LS is proposed by [I-D.ietf-idr-te-lsp-distribution]. The characteristics of an SR policy can be described by a TE Policy State TLV, which is carried in the optional non-transitive BGP Attribute "LINK_STATE Attribute" defined in [RFC7752]. The TE Policy State TLV contains several sub- TLVs such as SR TE Policy sub-TLVs. Rather than replicating SR TE Policy sub-TLVs, [I-D.ietf-idr-te-lsp-distribution] reuses the equivalent sub-TLVs as defined in [I-D.ietf-idr-segment-routing-te-policy]. As defined in [I-D.li-idr-sr-policy-path-segment-distribution], the new SR policies for bi-directional path has the following format: Li, et al. Expires October 6, 2018 [Page 3] Internet-Draft Path ID and Bi-directional Path in BGP-LS April 2018 SR Policy SAFI NLRI: Attributes: Tunnel Encaps Attribute (23) Tunnel Type: SR Policy Binding SID Preference Bi-directioanl Path Segment List Weight Path ID Segment Segment ... Reverse Segment List Weight Path ID Segment Segment ... Figure 1. SR policy for Bi-directional path For collecting configuration and states of uni-directional and bi- directional SR policies defined in [I-D.li-idr-sr-policy-path-segment-distribution], new sub-TLVs in SR TE Policy sub-TLVs should be defined. Likewise, rather than replicating SR Policy sub-TLVs, this document can reuse the equivalent sub-TLVs as defined in [I-D.li-idr-sr-policy-path-segment-distribution]. 3.1. SR Path ID Sub-TLV This section defines an SR Path ID sub-TLV to specify an SR path, and it is included in the Segment List sub-TLV as defined in [I-D.ietf-idr-te-lsp-distribution]. An SR Path ID sub-TLV is associated with an SR path specified by a Segment List sub-TLV, and it MUST appear only once within a Segment List sub-TLV. It 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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Type | Length | Flag | PIT | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Path ID (Variable) | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Figure 2. Path ID sub-TLV Li, et al. Expires October 6, 2018 [Page 4] Internet-Draft Path ID and Bi-directional Path in BGP-LS April 2018 All fields, including type and length, are defined in [I-D.li-idr-sr-policy-path-segment-distribution]. 3.2. Sub-TLVs for Bi-directional Path In some scenarios like mobile backhaul transport network, there are requirements to support bi-directional path. In SR, a bi-directional path can be represented as a binding of two uni-directional SR paths [I-D.cheng-spring-mpls-path-segment]. [I-D.li-idr-sr-policy-path-segment-distribution] defines new sub-TLVs to describe an SR bi-directional path. An SR policy carrying SR bi- directional path information is expressed in Figure 1. 3.2.1. SR Bi-directional Path Sub-TLV This section defines an SR bi-directional path sub-TLV to specify a bi-directional path, which contains a Segment List sub-TLV [I-D.ietf-idr-segment-routing-te-policy] and an associated Reverse Path Segment List as defined in [I-D.li-idr-sr-policy-path-segment-distribution]. The SR bi- directional path 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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Type | Length | RESERVED | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Sub-TLVs (Variable) | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Figure 3. SR Bi-directional path sub-TLV All fields, including type and length, are defined in [I-D.li-idr-sr-policy-path-segment-distribution]. 3.2.2. SR Reverse Path Segment List Sub-TLV This section defines an SR Reverse Path Segment List sub-TLV to specify an SR reverse path associated with the path specified by the Segment List in the same SR Bi-directional Path Sub-TLV, and it has the following format: Li, et al. Expires October 6, 2018 [Page 5] Internet-Draft Path ID and Bi-directional Path in BGP-LS April 2018 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 | RESERVED | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Sub-TLVs (Variable) | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Figure 4. SR Reverse Path Segment List Sub-TLV All fields, including type and length, are defined in [I-D.li-idr-sr-policy-path-segment-distribution]. 4. Operations No new operation procedures are defined in this document, the operations procedures of [RFC7752] can apply to this document. Typically but not limited to, the uni/bi-directional SR policies carrying path identification information can be distributed by the ingress node. Generally, BGP-LS is used for collecting link states and synchronizing with the external component. The consumer of the uni/ bi-directional SR policies carrying path identification information is not BGP LS process by itself, and it can be any applications such as performance measurement and path re-coputation or re-optimization, etc. The operation of sending information to other precesses is out of scope of this document. 5. IANA Considerations TBA 6. Security Considerations TBA 7. Acknowledgements TBA 8. Normative References [I-D.cheng-spring-mpls-path-segment] Cheng, W., Wang, L., Li, H., Chen, M., Zigler, R., and S. Zhan, "Path Segment in MPLS Based Sement Routing Network", draft-cheng-spring-mpls-path-segment-01 (work in progress), March 2018. Li, et al. Expires October 6, 2018 [Page 6] Internet-Draft Path ID and Bi-directional Path in BGP-LS April 2018 [I-D.filsfils-spring-segment-routing-policy] Filsfils, C., Sivabalan, S., Raza, K., Liste, J., Clad, F., Talaulikar, K., Ali, Z., Hegde, S., daniel.voyer@bell.ca, d., Lin, S., bogdanov@google.com, b., Krol, P., Horneffer, M., Steinberg, D., Decraene, B., Litkowski, S., and P. Mattes, "Segment Routing Policy for Traffic Engineering", draft-filsfils-spring-segment- routing-policy-05 (work in progress), February 2018. [I-D.ietf-idr-segment-routing-te-policy] Previdi, S., Filsfils, C., Jain, D., Mattes, P., Rosen, E., and S. Lin, "Advertising Segment Routing Policies in BGP", draft-ietf-idr-segment-routing-te-policy-02 (work in progress), March 2018. [I-D.ietf-idr-te-lsp-distribution] Previdi, S., Dong, J., Chen, M., Gredler, H., and J. Tantsura, "Distribution of Traffic Engineering (TE) Policies and State using BGP-LS", draft-ietf-idr-te-lsp- distribution-08 (work in progress), December 2017. [I-D.ietf-spring-segment-routing] Filsfils, C., Previdi, S., Ginsberg, L., Decraene, B., Litkowski, S., and R. Shakir, "Segment Routing Architecture", draft-ietf-spring-segment-routing-15 (work in progress), January 2018. [I-D.li-idr-sr-policy-path-segment-distribution] Li, C., Chen, M., Dong, J., and Z. Li, "Segment Routing Policies for Path Segment and Bi-directional Path", draft- li-idr-sr-policy-path-segment-distribution-00 (work in progress), April 2018. [I-D.li-spring-passive-pm-for-srv6-np] Li, C. and M. Chen, "Passive Performance Measurement for SRv6 Network Programming", draft-li-spring-passive-pm-for- srv6-np-00 (work in progress), March 2018. [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, DOI 10.17487/RFC2119, March 1997, . [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, . Li, et al. Expires October 6, 2018 [Page 7] Internet-Draft Path ID and Bi-directional Path in BGP-LS April 2018 Authors' Addresses Cheng Li Huawei Technologies Huawei Campus, No. 156 Beiqing Rd. Beijing 100095 China Email: chengli13@huawei.com Mach(Guoyi) Chen Huawei Technologies Huawei Campus, No. 156 Beiqing Rd. Beijing 100095 China Email: Mach.chen@huawei.com Jie Dong Huawei Technologies Huawei Campus, No. 156 Beiqing Rd. Beijing 100095 China Email: jie.dong@huawei.com Zhenbin Li Huawei Technologies Huawei Campus, No. 156 Beiqing Rd. Beijing 100095 China Email: lizhenbin@huawei.com Li, et al. Expires October 6, 2018 [Page 8]