LSR Working Group W. Britto Internet-Draft S. Hegde Intended status: Standards Track P. Kaneriya Expires: April 2, 2021 R. Shetty R. Bonica Juniper Networks September 29, 2020 IGP Flexible Algorithms (Flexalgo) In IP Networks draft-bonica-lsr-ip-flexalgo-00 Abstract An IGP Flexible Algorithm computes a constraint-based path and maps that path to an identifier. As currently defined, Flexalgo can only map the paths that it computes to Segment Routing (SR) identifiers. Therefore, Flexalgo cannot be deployed in the absence of SR. This document extends Flexalgo, so that it can map the paths that it computes to IP addresses. This allows Flexalgo to be deployed in any IP network, even in the absence of SR. 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 April 2, 2021. Copyright Notice Copyright (c) 2020 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 Britto, et al. Expires April 2, 2021 [Page 1] Internet-Draft IP Flexalgo September 2020 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. Egress Node Procedures . . . . . . . . . . . . . . . . . . . 3 4. Advertising Flexible Algorithm Definitions (FAD) . . . . . . 3 5. Advertising IP Reachability Using a Flexalgo . . . . . . . . 4 5.1. The ISIS IPv4 Flexalgo Prefix Reachability TLV . . . . . 4 5.2. The ISIS IPv6 Flexalgo Prefix Reachability TLV . . . . . 5 5.3. The ISIS MT IPv4 Flexalgo Prefix Reachability TLV . . . . 5 5.4. The ISIS MT IPv6 Flexalgo Prefix Reachability TLV . . . . 6 5.5. The OSPFv2 Flexalgo IP Prefix Opaque LSA . . . . . . . . 6 6. Advertising IGP Algorithm Support . . . . . . . . . . . . . . 8 6.1. The ISIS IGP Algorithm Sub-TLV . . . . . . . . . . . . . 8 6.2. The OSPFv2 IGP Algorithm TLV . . . . . . . . . . . . . . 9 7. Advertising Link Attributes . . . . . . . . . . . . . . . . . 10 8. Calculating Constraint-Based Paths . . . . . . . . . . . . . 10 9. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 10 10. Security Considerations . . . . . . . . . . . . . . . . . . . 11 11. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 11 12. References . . . . . . . . . . . . . . . . . . . . . . . . . 11 12.1. Normative References . . . . . . . . . . . . . . . . . . 11 12.2. Informative References . . . . . . . . . . . . . . . . . 13 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 13 1. Introduction An IGP Flexible Algorithm (Flexalgo) [I-D.ietf-lsr-flex-algo]: o Computes a constraint-based path to an egress node. o Maps that path to an identifier. As currently defined, Flexalgo can only map the paths that it computes to: o A Segment Routing (SR) [RFC8402] Segment Identifier (SID). o An SRv6 [I-D.ietf-spring-srv6-network-programming] locator. Therefore, Flexalgo cannot be deployed in the absence of SR and SRv6. Britto, et al. Expires April 2, 2021 [Page 2] Internet-Draft IP Flexalgo September 2020 This document extends Flexalgo, allowing it to map the paths that it computes to: o An IPv4 [RFC0791] address. o An IPv6 [RFC8200] address. This allows Flexalgo to be deployed in any IP network, even in the absence of SR and SRv6. 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. Egress Node Procedures Network operators configure multiple loopback interfaces on an egress node. They can associate each loopback interface with: o Zero or more IP addresses. o Zero or one Flexible Algorithms. If an IP address and a Flexible Algorithm are associated with the same interface, they are also associated with one another. An IP address MAY be associated with, at most, one interface. If a packet is sent to a loopback address, and the loopback address is not associated with a Flexible Algorithm, the packet follows the IGP least-cost path to the egress node. If a packet is sent to a loopback address, and the loopback address is associated with a Flexible Algorithm, the packet follows the constraint-base path that the Flexible Algorithm calculated. 4. Advertising Flexible Algorithm Definitions (FAD) To guarantee loop free forwarding, all routers that participate in a Flexible Algorithm MUST agree on the Flexible Algorithm Definition (FAD). Selected nodes within the IGP domain MUST advertise FADs as described in Sections 5, 6 and 7 of [I-D.ietf-lsr-flex-algo]. Britto, et al. Expires April 2, 2021 [Page 3] Internet-Draft IP Flexalgo September 2020 5. Advertising IP Reachability Using a Flexalgo ISIS [ISO10589] nodes use the following TLVs to advertise prefix reachability to prefixes that are associated with a Flexible Algorithm. o The IPv4 Flexalgo Prefix Reachability TLV o The IPv6 Flexalgo Prefix Reachability TLV o The MT IPv4 Flexalgo Prefix Reachability TLV o The MT IPv6 Flexalgo Prefix Reachability TLV OSPFv2 [RFC2328] nodes use the OSPFv2 Flexalgo IP Prefix Opaque LSA to advertise prefix reachability to prefixes that are associated with a Flexible Algorithm. 5.1. The ISIS IPv4 Flexalgo Prefix Reachability TLV 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 |U| Reserved |Flex-Algorithm | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Metric | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Prefix Len | Prefix ... +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |Sub-TLV Len(*) | Sub-TLVs(*) ... * - if present Figure 1: The ISIS IPv4 Flexalgo Prefix Reachability TLV Figure 1 represents the ISIS IPv4 Flexalgo Prefix Reachability TLV. It contains the following fields: o Type (8 bits): IPv4 Flexalgo Prefix Reachability TLV. Value TBD by IANA. o Length (8 bits) : TLV length. Measured in bytes. o U (1 bit): Set indicates up. Clear indicates down. o Reserved (7 bits): SHOULD be set to 0 by sender. MUST be ignored by receiver. Britto, et al. Expires April 2, 2021 [Page 4] Internet-Draft IP Flexalgo September 2020 o Flex-Algorithm (8 bits): Flexible Algorithm mapped to a prefix. o Metric (32 bits): As described in [RFC5305]. o Prefix Len (8 bits): Prefix length measured in bits. o Prefix (variable length): Prefix mapped to Flexible Algorithm. o Sub-TLV Len (8 bits): Optional. Sub-TLV length in bytes. o Sub-TLVs (variable length): Optional 5.2. The ISIS IPv6 Flexalgo Prefix Reachability TLV The ISIS IPv6 Flexalgo Prefix Reachability TLV is identical to the ISIS IPv4 Flexalgo Prefix Reachability TLV except that it has a unique type, The type is TBD by IANA. 5.3. The ISIS MT IPv4 Flexalgo Prefix Reachability TLV 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 | MTID | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |Flex-Algorithm |U| Reserved | Metric .. | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | .. Metric | Prefix Len | Prefix ... +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |Sub-TLV Len(*) | Sub-TLVs(*) ... * - if present Figure 2: The ISIS MT IPv4 Flexalgo Prefix Reachability TLV Figure 2 represents the ISIS MT IPv4 Flexalgo Prefix Reachability TLV. It contains the following fields: o Type (8 bits): MT IPv4 Flexalgo Prefix Reachability TLV. Value TBD by IANA. o Length (8 bits) : TLV length. Measured in bytes. o Reserved (8 bits): SHOULD be set to 0 by sender. MUST be ignored by receiver. Britto, et al. Expires April 2, 2021 [Page 5] Internet-Draft IP Flexalgo September 2020 o MTID: Multitopology Identifier as defined in [RFC5120]. Note that the value 0 is legal. o Flex-Algorithm (8 bits): Flexible Algorithm mapped to a prefix. o U (1 bit): Set indicates up. Clear indicates down. o Reserved (7 bits): SHOULD be set to 0 by sender. MUST be ignored by receiver. o Metric (32 bits): As described in [RFC5305]. o Prefix Len (8 bits): Prefix length measured in bits. o Prefix (variable length): Prefix mapped to Flexible Algorithm. o Sub-TLV Len (8 bits): Optional. Sub-TLV length in bytes. o Sub-TLVs (variable length): Optional 5.4. The ISIS MT IPv6 Flexalgo Prefix Reachability TLV The ISIS MT IPv6 Flexalgo Prefix Reachability TLV is identical to the ISIS MT IPv4 Flexalgo Prefix Reachability TLV except that it has a unique type, The type is TBD by IANA. 5.5. The OSPFv2 Flexalgo IP Prefix Opaque LSA The Flexalgo IP Prefix Opaque LSA begins with the standard LSA header (Figure 3). It contains the OSPFv2 Flexalgo IP Prefix TLV (Figure 4). Britto, et al. Expires April 2, 2021 [Page 6] Internet-Draft IP Flexalgo September 2020 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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | LS age | Options | 10 or 11 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | 11 | 0 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Advertising Router | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | LS sequence number | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | LS checksum | length | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | | +- TLVs -+ | ... | Figure 3: Standard LSA Header 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(1) | Length | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Reserved | Prefix Length | MT-ID |Flex-Algorithm | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Metric | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Prefix (variable) | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Sub-TLVs (variable) | +- -+ | ... | Figure 4: OSPFv2 Flexalgo IP Prefix TLV Figure 4 represents the OSPFv2 Flexalgo IP Prefix TLV. It contains the following fields: o Type (8 bits): MT IPv4 Flexalgo Prefix Reachability TLV. Value TBD by IANA. o Length (8 bits) : TLV length. Measured in bytes. o Reserved (8 bits): SHOULD be set to 0 by sender. MUST be ignored by receiver. o Prefix Len (8 bits): Prefix length measured in bits. Britto, et al. Expires April 2, 2021 [Page 7] Internet-Draft IP Flexalgo September 2020 o MTID: Multitopology Identifier as defined in [RFC4915]. Note that the value 0 is legal. o Flex-Algorithm (8 bits): Flexible Algorithm mapped to a prefix. o Metric (32 bits): As described in [RFC3630]. o Prefix (variable length): Prefix mapped to Flexible Algorithm. o Sub-TLVs (variable length): Optional 6. Advertising IGP Algorithm Support A node may use various algorithms when calculating paths. Algorithm values are defined in the IGP Algorithm Type Registry [IANA-ALG]. The following values have been defined: 1. SPF algorithm based on link metric. This is the well-known shortest path algorithm as computed by the IS-IS Decision Process. Consistent with the deployed practice for link-state protocols, algorithm 0 permits any node to overwrite the SPF path with a different path based on local policy. 2. Strict SPF algorithm based on link metric. The algorithm is identical to algorithm 0, but algorithm 1 requires that all nodes along the path will honor the SPF routing decision. Local policy MUST NOT alter the forwarding decision computed by algorithm 1 at the node claiming to support algorithm 1. ISIS and OSPFv2 use an IGP Algorithm TLV or sub-TLV to advertise IGP Algorithms that they support. 6.1. The ISIS IGP Algorithm Sub-TLV The IGP Algorithm Sub-TLV is advertised in the ISIS Router Capability TLV. The Router Capability TLV specifies flags that control its advertisement. The IGP Algorithm MUST be propagated throughout the level and MUST NOT be advertised across level boundaries. Therefore, Router Capability TLV distribution flags are set accordingly, i.e., the S-Flag MUST NOT be set. The IGP Algorithm sub-TLV is optional. It MUST NOT be advertised more than once at a given level. A router receiving multiple IGP Algorithm sub-TLVs from the same originator SHOULD select the first advertisement in the lowest-numbered LSP. Britto, et al. Expires April 2, 2021 [Page 8] Internet-Draft IP Flexalgo September 2020 When the originating router does not advertise the IGP Algorithm sub- TLV, it implies that algorithm 0 is the only algorithm supported by the routers that support the extensions defined in this document. When the originating router does advertise the IGP Algorithm sub-TLV, then algorithm 0 MUST be present while non-zero algorithms MAY be present. 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 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Algorithm 1 | Algorithm 2 | Algorithm ... | Algorithm n | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Figure 5: ISIS IGP Algorithm Sub-TLV Figure 5 depicts the IGP Algorithm Sub-TLV where: o Type: IGP Algorithm (Value TBD by IANA) o Length: Variable o Algorithm: 1 octet of algorithm. 6.2. The OSPFv2 IGP Algorithm TLV The IGP Algorithm TLV is a top-level TLV of the Router Information Opaque LSA [RFC7770]. The IGP Algorithm TLV is optional. It SHOULD only be advertised once in the Router Information Opaque LSA. If the IGP Algorithm TLV is not advertised by the node, the node is assumed to support algorithm 0 only. When multiple IGP Algorithm TLVs are received from a given router, the receiver MUST use the first occurrence of the TLV in the Router Information Opaque LSA. If the IGP Algorithm TLV appears in multiple Router Information Opaque LSAs that have different flooding scopes, the IGP Algorithm TLV in the Router Information Opaque LSA with the area-scoped flooding scope MUST be used. If the IGP Algorithm TLV appears in multiple Router Information Opaque LSAs that have the same flooding scope, the IGP Algorithm TLV in the Router Information (RI) Opaque LSA with the numerically smallest Instance ID MUST be used and subsequent instances of the IGP Algorithm TLV MUST be ignored. Britto, et al. Expires April 2, 2021 [Page 9] Internet-Draft IP Flexalgo September 2020 The RI LSA can be advertised at any of the defined opaque flooding scopes (link, area, or Autonomous System (AS)). For the purpose of IGP Algorithm TLV advertisement, area-scoped flooding is REQUIRED. 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 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Algorithm 1 | Algorithm... | Algorithm n | | +- -+ | | + + Figure 6: OSPFv2 IGP Algorithm TLV Figure 6 depicts the IGP Algorithm TLV where: o Type: IGP Algorithm (Value TBD by IANA) o Length: Variable o Algorithm: 1 octet of algorithm. 7. Advertising Link Attributes Various link attributes may be used during the Flex-Algorithm path calculation. Section 12 of [I-D.ietf-lsr-flex-algo] describes link advertisement procedures. 8. Calculating Constraint-Based Paths Nodes calculate constraint-based paths as described in Section 12 of [I-D.ietf-lsr-flex-algo]. 9. IANA Considerations This specification updates the OSPF Router Information (RI) TLVs Registry as follows: +-------+---------------+---------------+ | Value | TLV Name | Reference | +-------+---------------+---------------+ | TBD | IGP Algorithm | This Document | +-------+---------------+---------------+ This document also updates the "Sub-TLVs for TLV 242" registry as follows: Britto, et al. Expires April 2, 2021 [Page 10] Internet-Draft IP Flexalgo September 2020 +-------+---------------+---------------+ | Value | TLV Name | Reference | +-------+---------------+---------------+ | TBD | IGP Algorithm | This Document | +-------+---------------+---------------+ This document also updates the "ISIS TLV Codepoints Registry" registry as follows: +-------+------------------------------------------+---------------+ | Value | TLV Name | Reference | +-------+------------------------------------------+---------------+ | TBD | IPv4 Flexalgo Prefix Reachability TLV | This document | | TBD | IPv6 Flexalgo Prefix Reachability TLV | This document | | TBD | MT IPv4 Flexalgo Prefix Reachability TLV | This document | | TBD | MT IPv6 Flexalgo Prefix Reachability TLV | This document | +-------+------------------------------------------+---------------+ This document updates the "Opaque Link-State Advertisements (LSA) Option Types" registry as follows:: +-------+---------------------------------------+---------------+ | Value | TLV Name | Reference | +-------+---------------------------------------+---------------+ | TBD | OSPFvv2 Flexalgo IP Prefix Opaque LSA | This Document | +-------+---------------------------------------+---------------+ 10. Security Considerations TBD 11. Acknowledgements TBD. 12. References 12.1. Normative References [I-D.ietf-lsr-flex-algo] Psenak, P., Hegde, S., Filsfils, C., Talaulikar, K., and A. Gulko, "IGP Flexible Algorithm", draft-ietf-lsr-flex- algo-11 (work in progress), September 2020. Britto, et al. Expires April 2, 2021 [Page 11] Internet-Draft IP Flexalgo September 2020 [ISO10589] IANA, "Intermediate system to Intermediate system routing information exchange protocol for use in conjunction with the Protocol for providing the Connectionless-mode Network Service (ISO 8473)", August 1987, . [RFC0791] Postel, J., "Internet Protocol", STD 5, RFC 791, DOI 10.17487/RFC0791, September 1981, . [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, DOI 10.17487/RFC2119, March 1997, . [RFC2328] Moy, J., "OSPF Version 2", STD 54, RFC 2328, DOI 10.17487/RFC2328, April 1998, . [RFC3630] Katz, D., Kompella, K., and D. Yeung, "Traffic Engineering (TE) Extensions to OSPF Version 2", RFC 3630, DOI 10.17487/RFC3630, September 2003, . [RFC4915] Psenak, P., Mirtorabi, S., Roy, A., Nguyen, L., and P. Pillay-Esnault, "Multi-Topology (MT) Routing in OSPF", RFC 4915, DOI 10.17487/RFC4915, June 2007, . [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, . [RFC5305] Li, T. and H. Smit, "IS-IS Extensions for Traffic Engineering", RFC 5305, DOI 10.17487/RFC5305, October 2008, . [RFC5340] Coltun, R., Ferguson, D., Moy, J., and A. Lindem, "OSPF for IPv6", RFC 5340, DOI 10.17487/RFC5340, July 2008, . [RFC7770] Lindem, A., Ed., Shen, N., Vasseur, JP., Aggarwal, R., and S. Shaffer, "Extensions to OSPF for Advertising Optional Router Capabilities", RFC 7770, DOI 10.17487/RFC7770, February 2016, . Britto, et al. Expires April 2, 2021 [Page 12] Internet-Draft IP Flexalgo September 2020 [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, May 2017, . [RFC8200] Deering, S. and R. Hinden, "Internet Protocol, Version 6 (IPv6) Specification", STD 86, RFC 8200, DOI 10.17487/RFC8200, July 2017, . 12.2. Informative References [I-D.ietf-spring-srv6-network-programming] Filsfils, C., Camarillo, P., Leddy, J., Voyer, D., Matsushima, S., and Z. Li, "SRv6 Network Programming", draft-ietf-spring-srv6-network-programming-20 (work in progress), September 2020. [IANA-ALG] IANA, "Sub-TLVs for TLV 242 (IS-IS Router CAPABILITY TLV)", August 1987, . [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, . Authors' Addresses William Britto Juniper Networks Elnath-Exora Business Park Survey Bangalore, Karnataka 560103 India Email: bwilliam@juniper.net Shraddha Hegde Juniper Networks Elnath-Exora Business Park Survey Bangalore, Karnataka 560103 India Email: shraddha@juniper.net Britto, et al. Expires April 2, 2021 [Page 13] Internet-Draft IP Flexalgo September 2020 Parag Kaneriya Juniper Networks Elnath-Exora Business Park Survey Bangalore, Karnataka 560103 India Email: pkaneria@juniper.net Rejesh Shetty Juniper Networks Elnath-Exora Business Park Survey Bangalore, Karnataka 560103 India Email: mrajesh@juniper.net Ron Bonica Juniper Networks 2251 Corporate Park Drive Herndon, Virginia 20171 USA Email: rbonica@juniper.net Britto, et al. Expires April 2, 2021 [Page 14]