LSR Working Group T. Saad Internet-Draft V. Beeram Intended status: Standards Track Juniper Networks Expires: March 20, 2022 R. Chen S. Peng ZTE Corporation B. Wen Comcast D. Ceccarelli Ericsson September 16, 2021 IGP Extensions for SR Slice Aggregate SIDs draft-bestbar-lsr-spring-sa-01 Abstract Segment Routing (SR) defines a set of topological "segments" within an IGP topology to enable steering over a specific SR path. These segments are advertised by the link-state routing protocols (IS-IS and OSPF). This document describes extensions to the IS-IS that enable advertising Slice Aggregate SR segments that share the same IGP computed forwarding path but offer a forwarding treatment (e.g. scheduling and drop policy) that is associated with a specific Slice Aggregate. 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 March 20, 2022. Saad, et al. Expires March 20, 2022 [Page 1] Internet-Draft IGP SR Slice Aggregate SIDs September 2021 Copyright Notice Copyright (c) 2021 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. 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. Requirements Language . . . . . . . . . . . . . . . . . . . . 3 3. Slice Aggregate SIDs for SR-MPLS . . . . . . . . . . . . . . 3 3.1. IS-IS Slice Aggregate Prefix-SID Sub-TLV . . . . . . . . 3 3.2. IS-IS Slice Aggregate Adjacency-SID Sub-TLV . . . . . . . 5 3.3. IS-IS Slice Aggregate LAN Adjacency-SIDs . . . . . . . . 6 4. Slice Aggregate SIDs for SRv6 . . . . . . . . . . . . . . . . 7 4.1. SRv6 SID Slice Aggregate Sub-Sub-TLV . . . . . . . . . . 7 5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 8 5.1. SR Slice Aggregate Prefix-SID sub-TLV . . . . . . . . . . 9 5.2. SR Slice Aggregate Adjacency-SID sub-TLV . . . . . . . . 9 5.3. SR Slice Aggregate LAN-Adj-SID sub-TLV . . . . . . . . . 9 5.4. SRv6 SID Slice Aggregate Sub-Sub-TLV . . . . . . . . . . 9 6. Security Considerations . . . . . . . . . . . . . . . . . . . 9 7. Acknowledgement . . . . . . . . . . . . . . . . . . . . . . . 9 8. Contributors . . . . . . . . . . . . . . . . . . . . . . . . 9 9. References . . . . . . . . . . . . . . . . . . . . . . . . . 10 9.1. Normative References . . . . . . . . . . . . . . . . . . 10 9.2. Informative References . . . . . . . . . . . . . . . . . 11 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 12 1. Introduction The Segment Routing (SR) architecture [RFC8402] defines a set of topological "segments" within an IGP topology as means to enable steering over a specific SR end-to-end path. These segments are advertised by the IGP link-state routing protocols (IS-IS and OSPF). The SR control plane can be applied to both IPv6 and MPLS data planes. Saad, et al. Expires March 20, 2022 [Page 2] Internet-Draft IGP SR Slice Aggregate SIDs September 2021 The definition of a network slice for use within the IETF and the characteristics of IETF network slice are specified in [I-D.ietf-teas-ietf-network-slice-definition]. A framework for reusing IETF VPN and traffic-engineering technologies to realize IETF network slices is discussed in [I-D.nsdt-teas-ns-framework]. [I-D.bestbar-teas-ns-packet] introduces the notion of a Slice Aggregate as the construct that comprises of one of more IETF network slice traffic streams. A slice policy can be used to realize a slice aggregate by instantiating specific control and data plane resources on select topological elements in an IP/MPLS network. [I-D.bestbar-spring-scalable-ns] describes an approach to extend SR to advertiser new SID types called Slice Aggregate (SA) SIDs. Such SA SIDs are used on a router to define the forwarding action for a packet (next-hop selection), as well as enforce the specific treatment (scheduling and drop policy) associated with the Slice Aggregate. This document defines the IS-IS and OSPF encodings for the IGP-Prefix Segment, the IGP-Adjacency Segment, the IGP-LAN-Adjacency Segment that are required to support the signaling of SR Slice Aggregate SIDs operating over SR-MPLS and SRv6 dataplanes. When the Slice Aggregate segments have the same topology (and Algorithm for Prefix-SIDs), the SA SIDs share the same forwarding path (IGP next-hop(s)), but are associated with different forwarding treatment (e.g. scheduling and drop policy) that is associated with the specific Slice Aggregate. 2. 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. 3. Slice Aggregate SIDs for SR-MPLS Segment Routing can be directly instantiated on the MPLS data plane through the use of the Segment Routing header instantiated as a stack of MPLS labels defined in [RFC8402]. 3.1. IS-IS Slice Aggregate Prefix-SID Sub-TLV [RFC8667] defines the IS-IS Prefix Segment Identifier sub-TLV (Prefix-SID sub-TLV) that is applicable to SR-MPLS dataplane. The Prefix-SID sub-TLV carries the Segment Routing IGP-Prefix-SID, and is associated with a prefix advertised by a router. Saad, et al. Expires March 20, 2022 [Page 3] Internet-Draft IGP SR Slice Aggregate SIDs September 2021 A new IS-IS SR Slice Aggregate Prefix-SID (SA Prefix-SID) sub-TLV is defined to allow a router advertising a prefix to associate multiple SA Prefix-SIDs to the same prefix. The SA Prefix-SIDs associated with the same prefix share the same IGP path to the destination prefix within the specific mapped or customized topology/algorithm but offer the specific QoS treatment associated with the specific Slice Aggregate. The Slice Aggregate ID is carried in the SA Prefix-SID sub-TLV to associate it to Prefix-SID with a specific Slice Aggregate. The SA Prefix-SID 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=TBD1 | Length | Flag | Algorithm | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | SA-ID | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | SID/Index/Label(Variable) | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Figure 1: SA Prefix-SID sub-TLV for SR-MPLS. where: Type: TBD1 (Suggested value to be assigned by IANA) Length: Variable. Depending on the size of the SID. The "Flags" and "SID/Index/Label" fields are the same as the Prefix-SID sub-TLV [RFC8667]. Algorithm: 1 octet. Associated algorithm. Algorithm values are defined in the IGP Algorithm Type registry SA-ID: Identifies a specific Slice Aggregate within the IGP domain. This sub-TLV MAY be present in any of the following TLVs: TLV-135 (Extended IPv4 reachability) defined in [RFC5305]. TLV-235 (Multitopology IPv4 Reachability) defined in [RFC5120]. TLV-236 (IPv6 IP Reachability) defined in [RFC5308]. Saad, et al. Expires March 20, 2022 [Page 4] Internet-Draft IGP SR Slice Aggregate SIDs September 2021 TLV-237 (Multitopology IPv6 IP Reachability) defined in [RFC5120]. This sub-TLV MAY appear multiple times in each TLV. 3.2. IS-IS Slice Aggregate Adjacency-SID Sub-TLV [RFC8667] defines the IS-IS Adjacency Segment Identifier sub-TLV (Adj-SID sub-TLV). The Adj-SID sub-TLV is an optional sub-TLV carrying the Segment Routing IGP Adjacency-SID as defined in [RFC8402]. A new SR Slice Aggregate Adjacency-SID (SA Adj-SID) sub-TLV is defined to allow a router to allocate and advertise multiple SA Adj- SIDs towards the same IS-IS neighbor (adjacency). The SA Adj-SIDs allows a router to enforce the specific treatment associated with the Slice Aggregate. The Slice Aggregate ID is carried in the SA Adj-SID sub-TLV to associate it to the specific Slice Aggregate. The SA Adj-SID 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 | Flags | Weight | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | SA-ID | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | SID/Index/Label(Variable) | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Figure 2: SA Adj-SID sub-TLV for SR-MPLS. where: Type: TBD2 (Suggested value to be assigned by IANA) Length: Variable. Depending on the size of the SID. The "Flags" and "SID/Index/Label" fields are the same as the Adj- SID sub-TLV [RFC8667]. SA-ID: Identifies a specific Slice Aggregate within the IGP domain. This sub-TLV MAY be present in any of the following TLVs: TLV-22 (Extended IS reachability) [RFC5305]. Saad, et al. Expires March 20, 2022 [Page 5] Internet-Draft IGP SR Slice Aggregate SIDs September 2021 TLV-222 (Multitopology IS) [RFC5120]. TLV-23 (IS Neighbor Attribute) [RFC5311]. TLV-223 (Multitopology IS Neighbor Attribute) [RFC5311]. TLV-141 (inter-AS reachability information) [RFC5316]. Multiple Adj-SID sub-TLVs MAY be associated with a single IS-IS neighbor. This sub-TLV MAY appear multiple times in each TLV. 3.3. IS-IS Slice Aggregate LAN Adjacency-SIDs In LAN subnetworks, [RFC8667] defines the SR-MPLS LAN-Adj-SID sub-TLV for a router to advertise the Adj-SID of each of its neighbors. A new SR Slice Aggregate LAN Adjacency-SID (SA LAN-Adj-SID) sub-TLV is defined to allow a router to allocate and advertise multiple SA LAN-Adj-SIDs towards each of its neighbors on the LAN. The SA LAN- Adj-SIDs allows a router to enforce the specific treatment associated with the specific Slice Aggregate towards a neighbor. The Slice Aggregate ID is carried in the SA LAN-Adj-SID sub-TLV to associate it to the specific Slice Aggregate. The SA LAN-Adj-SID 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=TBD3 | Length | Flags | Weight | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | SA-ID | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Neighbor System-ID (ID length octets) | + +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | SID/Label/Index (variable) | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Figure 3: SA LAN Adj-SID sub-TLV for SR-MPLS. where: Saad, et al. Expires March 20, 2022 [Page 6] Internet-Draft IGP SR Slice Aggregate SIDs September 2021 Type: TBD3 (Suggested value to be assigned by IANA) Length: Variable. Depending on the size of the SID. The "Flags" and "SID/Index/Label" fields are the same as the LAN- Adj-SID sub-TLV [RFC8667]. SA-ID: Identifies a specific Slice Aggregate within the IGP domain. This sub-TLV MAY be present in any of the following TLVs: TLV-22 (Extended IS reachability) [RFC5305]. TLV-222 (Multitopology IS) [RFC5120]. TLV-23 (IS Neighbor Attribute) [RFC5311]. TLV-223 (Multitopology IS Neighbor Attribute) [RFC5311]. Multiple LAN-Adj-SID sub-TLVs MAY be associated with a single IS-IS neighbor. This sub-TLV MAY appear multiple times in each TLV. Editor Note: the OSPF Sub-TLV sections will be populated in further update. 4. Slice Aggregate SIDs for SRv6 Segment Routing can be directly instantiated on the IPv6 data plane through the use of the Segment Routing Header defined in [RFC8754]. SRv6 refers to this SR instantiation on the IPv6 dataplane. The SRv6 Locator TLV was introduced in [I-D.ietf-lsr-isis-srv6-extensions] to advertise SRv6 Locators and End SIDs associated with each locator. 4.1. SRv6 SID Slice Aggregate Sub-Sub-TLV The SRv6 End SID sub-TLV was introduced in [I-D.ietf-lsr-isis-srv6-extensions] to advertise SRv6 Segment Identifiers (SID) with Endpoint behaviors which do not require a particular neighbor. The SRv6 End SID sub-TLV is advertised in the SRv6 Locator TLV, and inherits the topology/algorithm from the parent locator. The SRv6 End SID sub-TLV defined in [I-D.ietf-lsr-isis-srv6-extensions] carries optional sub-sub-TLVs. Saad, et al. Expires March 20, 2022 [Page 7] Internet-Draft IGP SR Slice Aggregate SIDs September 2021 A new SRv6 Slice Aggregate (SA) SID Sub-Sub-TLV is defined to allow a router to assign and advertise an SRv6 End SID that is associated with a specific Slice Aggregate. The SRv6 SID SA Sub-Sub-TLV allows routers to infer and enforce the specific treatment associated with the Slice Aggregate on the selected next-hops along the path to the End SID destination. 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=TBD4 | Length | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | SA-ID | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Figure 4: SRv6 SID SA Sub-Sub-TLV format for SRv6. where: Type: TBD4 Length: 4 octets. SA-ID: Identifies a specific Slice Aggregate within the IGP domain. ISIS SRv6 SID SA Sub-Sub-TLV MUST NOT appear more than once in its parent Sub-TLV. If it appears more than once in its parent Sub- TLV, the parent Sub-TLV MUST be ignored by the receiver. The new SRv6 SID SA Sub-Sub-TLV is an optional Sub-Sub-TLV of: SRv6 End SID Sub-TLV (Section 7.2 of [I-D.ietf-lsr-isis-srv6-extensions]) SRv6 End.X SID Sub-TLV (Section 8.1 of [I-D.ietf-lsr-isis-srv6-extensions]) SRv6 LAN End.X SID Sub-TLV (Section 8.2 of [I-D.ietf-lsr-isis-srv6-extensions]) 5. IANA Considerations This document requests allocation for the following Sub-TLVs. Saad, et al. Expires March 20, 2022 [Page 8] Internet-Draft IGP SR Slice Aggregate SIDs September 2021 5.1. SR Slice Aggregate Prefix-SID sub-TLV This TLV shares sub-TLV space with existing "Sub-TLVs for TLVs 135,235,226 and 237 registry". Type: TBD1 (to be assigned by IANA). 5.2. SR Slice Aggregate Adjacency-SID sub-TLV This TLV shares sub-TLV space with existing "Sub-TLVs for TLVs 22, 222, 23, 223 and 141 registry". Type: TBD2 (to be assigned by IANA). 5.3. SR Slice Aggregate LAN-Adj-SID sub-TLV This TLV shares sub-TLV space with existing "Sub-TLVs for TLVs 22, 222, 23, and 223 registry". Type: TBD3 (to be assigned by IANA). 5.4. SRv6 SID Slice Aggregate Sub-Sub-TLV Type: TBD4 (to be assigned by IANA). 6. Security Considerations TBD. 7. Acknowledgement The authors would like to thank Swamy SRK, and Prabhu Raj Villadathu Karunakaran for their review of this document, and for providing valuable feedback on it. 8. Contributors The following individuals contributed to this document: Saad, et al. Expires March 20, 2022 [Page 9] Internet-Draft IGP SR Slice Aggregate SIDs September 2021 Colby Barth Juniper Networks Email: cbarth@juniper.net Srihari R. Sangli Juniper Networks Email: ssangli@juniper.net Chandra Ramachandran Juniper Networks Email: csekar@juniper.net 9. References 9.1. Normative References [I-D.bestbar-spring-scalable-ns] Saad, T., Beeram, V. P., Chen, R., Peng, S., Wen, B., and D. Ceccarelli, "Scalable Network Slicing over SR Networks", draft-bestbar-spring-scalable-ns-02 (work in progress), September 2021. [I-D.bestbar-teas-ns-packet] Saad, T., Beeram, V. P., Wen, B., Ceccarelli, D., Halpern, J., Peng, S., Chen, R., Liu, X., Contreras, L. M., and R. Rokui, "Realizing Network Slices in IP/MPLS Networks", draft-bestbar-teas-ns-packet-03 (work in progress), July 2021. [I-D.ietf-lsr-isis-srv6-extensions] Psenak, P., Filsfils, C., Bashandy, A., Decraene, B., and Z. Hu, "IS-IS Extensions to Support Segment Routing over IPv6 Dataplane", draft-ietf-lsr-isis-srv6-extensions-17 (work in progress), June 2021. [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, DOI 10.17487/RFC2119, March 1997, . [RFC5120] Przygienda, T., Shen, N., and N. Sheth, "M-ISIS: Multi Topology (MT) Routing in Intermediate System to Intermediate Systems (IS-ISs)", RFC 5120, DOI 10.17487/RFC5120, February 2008, . Saad, et al. Expires March 20, 2022 [Page 10] Internet-Draft IGP SR Slice Aggregate SIDs September 2021 [RFC5305] Li, T. and H. Smit, "IS-IS Extensions for Traffic Engineering", RFC 5305, DOI 10.17487/RFC5305, October 2008, . [RFC5308] Hopps, C., "Routing IPv6 with IS-IS", RFC 5308, DOI 10.17487/RFC5308, October 2008, . [RFC5311] McPherson, D., Ed., Ginsberg, L., Previdi, S., and M. Shand, "Simplified Extension of Link State PDU (LSP) Space for IS-IS", RFC 5311, DOI 10.17487/RFC5311, February 2009, . [RFC5316] Chen, M., Zhang, R., and X. Duan, "ISIS Extensions in Support of Inter-Autonomous System (AS) MPLS and GMPLS Traffic Engineering", RFC 5316, DOI 10.17487/RFC5316, December 2008, . [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, 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, . [RFC8667] Previdi, S., Ed., Ginsberg, L., Ed., Filsfils, C., Bashandy, A., Gredler, H., and B. Decraene, "IS-IS Extensions for Segment Routing", RFC 8667, DOI 10.17487/RFC8667, December 2019, . [RFC8754] Filsfils, C., Ed., Dukes, D., Ed., Previdi, S., Leddy, J., Matsushima, S., and D. Voyer, "IPv6 Segment Routing Header (SRH)", RFC 8754, DOI 10.17487/RFC8754, March 2020, . 9.2. Informative References [I-D.ietf-teas-ietf-network-slice-definition] Rokui, R., Homma, S., Makhijani, K., Contreras, L. M., and J. Tantsura, "Definition of IETF Network Slices", draft- ietf-teas-ietf-network-slice-definition-01 (work in progress), February 2021. Saad, et al. Expires March 20, 2022 [Page 11] Internet-Draft IGP SR Slice Aggregate SIDs September 2021 [I-D.nsdt-teas-ns-framework] Gray, E. and J. Drake, "Framework for IETF Network Slices", draft-nsdt-teas-ns-framework-05 (work in progress), February 2021. Authors' Addresses Tarek Saad Juniper Networks Email: tsaad@juniper.net Vishnu Pavan Beeram Juniper Networks Email: vbeeram@juniper.net Ran Chen ZTE Corporation Email: chen.ran@zte.com.cn Shaofu Peng ZTE Corporation Email: peng.shaofu@zte.com.cn Bin Wen Comcast Email: Bin_Wen@cable.comcast.com Daniele Ceccarelli Ericsson Email: daniele.ceccarelli@ericsson.com Saad, et al. Expires March 20, 2022 [Page 12]