Multiprotocol Label Switching F. Ihle Internet-Draft University of Tuebingen Intended status: Standards Track X. Song Expires: 15 December 2025 ZTE Corporation M. Menth University of Tuebingen 13 June 2025 Signaling MNA Capabilities Using IGP draft-ihlesong-mpls-mna-signaling-00 Abstract This document defines capabilities of nodes supporting MPLS Network Actions (MNA) and how to signal them using IS-IS and OSPF. The capabilities include the Readable Label Depth (RLD), supported network action opcodes, and the maximum sizes of differently scoped Network Action Sub-stacks (NAS), called the NAS_MLD. For IS-IS and OSPF signaling, sub-TLV encodings based on existing mechanisms to signal node- and link-specific capabilities are leveraged. About This Document This note is to be removed before publishing as an RFC. The latest revision of this draft can be found at https://uni-tue- kn.github.io/draft-ihle-song-mpls-mna-signaling/draft-ihle-song-mpls- mna-signaling.html. Status information for this document may be found at https://datatracker.ietf.org/doc/draft-ihlesong-mpls-mna- signaling/. Discussion of this document takes place on the Multiprotocol Label Switching Working Group mailing list (mailto:mpls@ietf.org), which is archived at https://mailarchive.ietf.org/arch/browse/mpls/. Subscribe at https://www.ietf.org/mailman/listinfo/mpls/. Source for this draft and an issue tracker can be found at https://github.com/uni-tue-kn/draft-ihlesong-mpls-mna-signaling. Status of This Memo This Internet-Draft is submitted in full conformance with the provisions of BCP 78 and BCP 79. Ihle, et al. Expires 15 December 2025 [Page 1] Internet-Draft SIG June 2025 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 15 December 2025. Copyright Notice Copyright (c) 2025 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 Revised BSD License text as described in Section 4.e of the Trust Legal Provisions and are provided without warranty as described in the Revised BSD License. Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3 1.1. Terminology . . . . . . . . . . . . . . . . . . . . . . . 3 1.1.1. Abbreviations . . . . . . . . . . . . . . . . . . . . 3 2. Definition of MNA Capabilities . . . . . . . . . . . . . . . 3 2.1. The Readable Label Depth (RLD) . . . . . . . . . . . . . 4 2.1.1. Example . . . . . . . . . . . . . . . . . . . . . . . 4 2.2. Maximum NAS Sizes . . . . . . . . . . . . . . . . . . . . 4 2.2.1. Motivation . . . . . . . . . . . . . . . . . . . . . 5 2.2.2. NAS Maximum Label Depth (NAS_MLD) . . . . . . . . . . 5 2.2.3. Example . . . . . . . . . . . . . . . . . . . . . . . 6 2.3. Supported Network Action Opcodes . . . . . . . . . . . . 7 3. Signaling MNA Capabilites . . . . . . . . . . . . . . . . . . 7 3.1. Using IS-IS . . . . . . . . . . . . . . . . . . . . . . . 7 3.1.1. NAS_MLD Advertisement . . . . . . . . . . . . . . . . 7 3.1.2. RLD Advertisment . . . . . . . . . . . . . . . . . . 8 3.1.3. Supported Network Action Opcodes . . . . . . . . . . 8 3.2. Using OSPF . . . . . . . . . . . . . . . . . . . . . . . 8 3.2.1. NAS_MLD Advertisement . . . . . . . . . . . . . . . . 8 3.2.2. RLD Advertisment . . . . . . . . . . . . . . . . . . 9 3.2.3. Supported Network Action Opcodes . . . . . . . . . . 9 Ihle, et al. Expires 15 December 2025 [Page 2] Internet-Draft SIG June 2025 4. Security Considerations . . . . . . . . . . . . . . . . . . . 10 5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 10 6. References . . . . . . . . . . . . . . . . . . . . . . . . . 10 6.1. Normative References . . . . . . . . . . . . . . . . . . 10 6.2. Informative References . . . . . . . . . . . . . . . . . 10 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 12 1. Introduction With the MPLS Network Action (MNA) framework, network actions are encoded in the MPLS stack. Those can be added to the MPLS tack using in-stack data (ISD), or follow after the MPLS stack using post-stack data (PSD). [I-D.ietf-mpls-mna-hdr] defines the encoding of such network actions and their data for ISD in a so-called Network Action Substack (NAS). These network actions are processed by all nodes on a path (hop-by-hop, HBH), by only selected nodes, or on an ingress- to-egress (I2E) basis. LSRs have different capabilites that depend on available hardware resources, e.g., the number of LSEs they can parse. An ingress LER that pushes network actions to an MPLS stack MUST ensure that all nodes on the path can read and support the network actions. For that purpose, the MNA capabilities of an LSR need to be signaled to the ingress LER. This document defines the required parameters of LSRs regarding their MNA capability and proposes a signaling extension using an IGP such as IS-IS and OSPF. 1.1. Terminology 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. 1.1.1. Abbreviations This document makes use of the terms defined in [I-D.ietf-mpls-mna-hdr] and in [I-D.ietf-mpls-mna-fwk]. 2. Definition of MNA Capabilities This section defines the parameters that an LSR uses to signal its MNA capabilities to the ingress LER. Ihle, et al. Expires 15 December 2025 [Page 3] Internet-Draft SIG June 2025 2.1. The Readable Label Depth (RLD) The Readable Label Depth (RLD) is the number of LSEs an LSR can parse without performance impact [I-D.ietf-mpls-mna-fwk]. An LSR is required to search the MPLS stack for NAS that have to be processed by the LSR. To that end, the network actions must be within the RLD of the node. For HBH-scoped network actions, the ingress LER that pushes the network actions MUST ensure that the actions are readable at each LSR on the path, i.e., that it is placed within the RLD of each node. 2.1.1. Example An example for the RLD parameter is given in Figure 1. With an RLD of 5, an LSR is capable of reading labels A, B, C, D, and E but not F. An RLD of 8 is required in this example to read the entire MPLS stack. 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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | MPLS-Label = A | TC |0| TTL | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | MPLS-Label = B | TC |0| TTL | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | MPLS-Label = C | TC |0| TTL | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | MPLS-Label = D | TC |0| TTL | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | MPLS-Label = E | TC |0| TTL | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | MPLS-Label = F | TC |0| TTL | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | MPLS-Label = G | TC |0| TTL | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | MPLS-Label = H | TC |1| TTL | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Figure 1: Example MPLS stack of 8 MPLS LSEs illustrating the concept of RLD. 2.2. Maximum NAS Sizes This section gives a motivation for signaling maximum NAS sizes and then introduces the NAS Maximum Label Depth (NAS_MLD). Ihle, et al. Expires 15 December 2025 [Page 4] Internet-Draft SIG June 2025 2.2.1. Motivation A NAS in the MNA header encoding is at least 2 LSEs and at most 17 LSEs large [I-D.ietf-mpls-mna-hdr]. At an LSR, one or more NAS, e.g., a select-scoped and a hop-by-hop-scoped NAS, are possible. With two maximum-sized NAS, an LSR is required to reserve 34 LSEs in hardware to be able to process network actions. This consumes hardware resources that may be needed to encode other LSEs, e.g., forwarding labels for SR-MPLS paths, or are not available in less capable devices. Many use cases in the MNA framework [I-D.ietf-mpls-mna-usecases] do not require a maximum-sized NAS of 17 LSEs to encode network actions and their ancillary data. Therefore, a NAS can be up to 17 LSEs but nodes can also support smaller maximum NAS. By signaling the maximum supported NAS size to the ingress LER, an LSR receiving packets with a larger NAS than supported is avoided. This way, the allocated resources for NAS can be reduced if smaller maximum NAS are supported. More resources are available for other purposes, and hardware with a low RLD can be made MNA-capable [IhMe25]. 2.2.2. NAS Maximum Label Depth (NAS_MLD) The maximum supported number of LSEs in a NAS that an LSR can process is referred to as NAS Maximum Label Depth (NAS_MLD) in this document. For each scope in MNA, a separate parameter for the NAS_MLD exists, called NAS_MLD_Select, NAS_MLD_HBH, and NAS_MLD_I2E. An LSR SHOULD signal the maximum-supported size of a NAS for each scope, i.e., the parameters NAS_MLD_Select, NAS_MLD_HBH, and NAS_MLD_I2E. Those parameters include the Format A, B, C, and D LSEs from [I-D.ietf-mpls-mna-hdr] in a NAS. Based on the signaled parameters, the ingress LER MUST ensure the following when pushing the MPLS stack and NAS on a packet: * The ingress LER MUST NOT push a select-scoped NAS that is larger than the signaled NAS_MLD_Select value of the node that will process the select-scoped NAS. * The ingress LER MUST NOT push an HBH-scoped NAS that is larger than the minimum of all signaled NAS_MLD_HBH values of all nodes on the path. * The ingress LER MUST NOT push an I2E-scoped NAS that is larger than the signaled NAS_MLD_I2E value of the egress node. Ihle, et al. Expires 15 December 2025 [Page 5] Internet-Draft SIG June 2025 2.2.3. Example Figure 1 illustrates the different NAS_MLD sizes in an MPLS stack that are signaled to the LSR. In this example, a select-scoped NAS has a maximum size of 4 LSEs, a hop-by-hop-scoped NAS of 7 LSEs, and an I2E-scoped NAS of 4 LSEs. +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | MPLS-Label = A | TC |0| TTL | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ──┑ | MNA-Label=bSPL (TBA) | TC |0| TTL | │ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ │ | Opcode | Data |R|SEL|0|U| NASL=2|NAL=0| │ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ NAS_MLD | Opcode | Data |0|U| Data |NAL=1| _Select +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ │ |1| Data |0| Data | │ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ──┚ | MPLS-Label = B | TC |0| TTL | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | MPLS-Label = C | TC |0| TTL | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ──┑ | MNA-Label=bSPL (TBA) | TC |0| TTL | │ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ │ | Opcode | Data |R|HBH|0|U| NASL=5|NAL=0| │ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ │ | Opcode | Data |0|U| Data |NAL=0| │ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ │ | Opcode | Data |0|U| Data |NAL=0| NAS_MLD +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ _HBH | Opcode | Data |0|U| Data |NAL=0| │ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ │ | Opcode | Data |0|U| Data |NAL=1| │ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ │ |1| Data |0| Data | │ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ───┨ | MNA-Label=bSPL (TBA) | TC |0| TTL | │ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ │ | Opcode | Data |R|I2E|0|U| NASL=2|NAL=0| │ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ NAS_MLD | Opcode | Data |0|U| Data |NAL=1| _I2E +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ │ |1| Data |1| Data | │ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ───┚ Figure 2: Example MPLS stack illustrating the different NAS sizes. Ihle, et al. Expires 15 December 2025 [Page 6] Internet-Draft SIG June 2025 2.3. Supported Network Action Opcodes An LSR MUST signal the network action opcodes it supports. If a network action opcode is not signaled, it is assumed that this opcode is not supported by the node. 3. Signaling MNA Capabilites This section defines a method for IGP routers to advertise the maximum supported numbers of LSEs in I2E-scoped NAS, select-scoped NAS, and HBH-scoped NAS, i.e., the per-scope NAS_MLD, the RLD, and supported opcodes. 3.1. Using IS-IS This section defines the signaling of the RLD and the NAS_MLD that can be supported for specific NAS using IS-IS node and link advertisement. [rfc7981] defines the IS-IS Router Capability TLV that supports optional sub-TLVs to signal capabilities. Further, [rfc8491] introduces a sub-TLV for node- and link-specific advertisement based on [rfc7981]. They are used to signal MNA capabilities with IS-IS. 3.1.1. NAS_MLD Advertisement To signal the per-scope NAS_MLD, this document introduces new sub- TLVs based on [rfc8491]. The NAS_MLD Sub-TLV is defined node- or link-specific as below: 0 1 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Type | Length | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | NAS_MLD Type | NAS_MLD Value | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ // ................... // +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | NAS_MLD Type | NAS_MLD Value | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Figure 3: NAS_MLD Sub-TLV for IS-IS signaling. * Type: - 15 (link-specifc) [rfc8491] - 23 (node-specific) [rfc8491] Ihle, et al. Expires 15 December 2025 [Page 7] Internet-Draft SIG June 2025 * Length: variable (multiple of 2 octets); represents the total length of the Value field * Value: field consists of one or more pairs of a 1-octet MSD-Type and 1-octet MSD-Value - NAS_MLD-Type: value defined in the "IGP MSD-Types" registry created by the IANA Considerations section of this document (I2E, HBH, or Select). - NAS_MLD-Value: number in the range of 2-17. This sub-TLV is optional. The scope of the advertisement is specific to the deployment. 3.1.2. RLD Advertisment For the RLD advertisement, a sub-TLV based on [rfc8491] is requested in [I-D.draft-ietf-mpls-mna-fwk]. 3.1.3. Supported Network Action Opcodes tbd 3.2. Using OSPF This section defines the signaling of the RLD and the NAS_MLD that can be supported for specific NAS using OSPF node and link advertisement. [rfc7770] defines the OSPF RI Opaque LSA which is used in [rfc8476] to carry the node-specific provisioned SID depth of the router originating the Router Information (RI) LSA in a sub-TLV. Further, [rfc7684] defines link-specific advertisements using the optional sub-TLV of the OSPFv2 Extended Link TLV for OSPFv2, and [rfc8362] defines link-specific advertisements using the optional sub-TLV of the E-Router-LSA TLV. 3.2.1. NAS_MLD Advertisement To signal the per-scope NAS_MLD, this document introduces new sub- TLVs based on [rfc7684], [rfc8476], and [rfc8362]. The NAS_MLD Sub- TLV is defined node- or link-specific as below: Ihle, et al. Expires 15 December 2025 [Page 8] Internet-Draft SIG June 2025 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 | +-------------------------------------------------------------+ | NAS_MLD Type | NAS_MLD Value | +-------------------------------------------------------------+ // ................... // +-------------------------------------------------------------+ | NAS_MLD Type | NAS_MLD Value | +-------------------------------------------------------------+ Figure 4: NAS_MLD Sub-TLV for OSPF signaling. * Type: - 6 (link-specific, OSPFv2 [RFC7684]) - 9 (link-specific, OSPFv3 [RFC8362]) - 12 (node-specific, OSPFv2 and OSPFv3 [rfc8476]) * Length: variable (in octets); represents the total length of the Value field * Value: field consists of one or more pairs of a 2-octet MSD-Type and 2-octet MSD-Value - NAS_MLD-Type: value defined in the "IGP MSD-Types" registry created by the IANA Considerations section of this document (I2E, HBH, or Select). - NAS_MLD-Value: number in the range of 2-17. This sub-TLV is optional. The scope of the advertisement is specific to the deployment. 3.2.2. RLD Advertisment For the RLD advertisement, a sub-TLV is requested in [I-D.draft-ietf-mpls-mna-fwk]. 3.2.3. Supported Network Action Opcodes tbd Ihle, et al. Expires 15 December 2025 [Page 9] Internet-Draft SIG June 2025 4. Security Considerations The security issues discussed in [I-D.ietf-mpls-mna-hdr], [rfc8476], and [rfc8491] apply to this document. 5. IANA Considerations This document requests the allocation of following codepoints in the "IGP MSD-Types" registry. +=======+================+=======+===============================+ | Value | Name | Data | Reference | | | | Plane | | +=======+================+=======+===============================+ | 3 | Readable Label | MPLS | [I-D.draft-ietf-mpls-mna-fwk] | | | Depth | | | +-------+----------------+-------+-------------------------------+ | 4 | MLD of select- | MPLS | This document | | | scoped NAS | | | +-------+----------------+-------+-------------------------------+ | 5 | MLD of I2E- | MPLS | This document | | | scoped NAS | | | +-------+----------------+-------+-------------------------------+ | 6 | MLD of HBH- | MPLS | This document | | | scoped NAS | | | +-------+----------------+-------+-------------------------------+ Table 1: IGP Signaling Sub-TLV allocation. 6. References 6.1. Normative References [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, DOI 10.17487/RFC2119, March 1997, . [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, May 2017, . 6.2. Informative References Ihle, et al. Expires 15 December 2025 [Page 10] Internet-Draft SIG June 2025 [I-D.draft-ietf-mpls-mna-fwk] Andersson, L., Bryant, S., Bocci, M., and T. Li, "MPLS Network Actions (MNA) Framework", Work in Progress, Internet-Draft, draft-ietf-mpls-mna-fwk-15, 27 December 2024, . [I-D.ietf-mpls-mna-fwk] Andersson, L., Bryant, S., Bocci, M., and T. Li, "MPLS Network Actions (MNA) Framework", Work in Progress, Internet-Draft, draft-ietf-mpls-mna-fwk-15, 27 December 2024, . [I-D.ietf-mpls-mna-hdr] Rajamanickam, J., Gandhi, R., Zigler, R., Song, H., and K. Kompella, "MPLS Network Action (MNA) Sub-Stack Solution", Work in Progress, Internet-Draft, draft-ietf-mpls-mna-hdr- 12, 3 March 2025, . [I-D.ietf-mpls-mna-usecases] Saad, T., Makhijani, K., Song, H., and G. Mirsky, "Use Cases for MPLS Network Action Indicators and MPLS Ancillary Data", Work in Progress, Internet-Draft, draft- ietf-mpls-mna-usecases-15, 23 September 2024, . [IhMe25] Ihle, F. and M. Menth, "MPLS Network Actions; Technological Overview and P4-Based Implementation on a High-Speed Switching ASIC", DOI 10.1109/OJCOMS.2025.3557082, 2 April 2025, . [rfc7684] Psenak, P., Gredler, H., Shakir, R., Henderickx, W., Tantsura, J., and A. Lindem, "OSPFv2 Prefix/Link Attribute Advertisement", RFC 7684, DOI 10.17487/RFC7684, November 2015, . [RFC7684] Psenak, P., Gredler, H., Shakir, R., Henderickx, W., Tantsura, J., and A. Lindem, "OSPFv2 Prefix/Link Attribute Advertisement", RFC 7684, DOI 10.17487/RFC7684, November 2015, . Ihle, et al. Expires 15 December 2025 [Page 11] Internet-Draft SIG June 2025 [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, . [rfc7981] Ginsberg, L., Previdi, S., and M. Chen, "IS-IS Extensions for Advertising Router Information", RFC 7981, DOI 10.17487/RFC7981, October 2016, . [rfc8362] Lindem, A., Roy, A., Goethals, D., Reddy Vallem, V., and F. Baker, "OSPFv3 Link State Advertisement (LSA) Extensibility", RFC 8362, DOI 10.17487/RFC8362, April 2018, . [RFC8362] Lindem, A., Roy, A., Goethals, D., Reddy Vallem, V., and F. Baker, "OSPFv3 Link State Advertisement (LSA) Extensibility", RFC 8362, DOI 10.17487/RFC8362, April 2018, . [rfc8476] Tantsura, J., Chunduri, U., Aldrin, S., and P. Psenak, "Signaling Maximum SID Depth (MSD) Using OSPF", RFC 8476, DOI 10.17487/RFC8476, December 2018, . [rfc8491] Tantsura, J., Chunduri, U., Aldrin, S., and L. Ginsberg, "Signaling Maximum SID Depth (MSD) Using IS-IS", RFC 8491, DOI 10.17487/RFC8491, November 2018, . Authors' Addresses Fabian Ihle University of Tuebingen Tuebingen Germany Email: fabian.ihle@uni-tuebingen.de Xueyan Song ZTE Corporation China Email: song.xueyan2@zte.com.cn Ihle, et al. Expires 15 December 2025 [Page 12] Internet-Draft SIG June 2025 Michael Menth University of Tuebingen Tuebingen Germany Email: michael.menth@uni-tuebingen.de Ihle, et al. Expires 15 December 2025 [Page 13]