Signaling MNA Capabilities Using IGP
draft-ihlesong-mpls-mna-signaling-00

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.

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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

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   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.

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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).

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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.

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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.

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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]

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   *  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:

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   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

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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,
              <https://www.rfc-editor.org/rfc/rfc2119>.

   [RFC8174]  Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
              2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
              May 2017, <https://www.rfc-editor.org/rfc/rfc8174>.

6.2.  Informative References

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   [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, <https://datatracker.ietf.org/doc/html/draft-ietf-
              mpls-mna-fwk-15>.

   [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, <https://datatracker.ietf.org/doc/html/draft-ietf-
              mpls-mna-fwk-15>.

   [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, <https://datatracker.ietf.org/doc/html/
              draft-ietf-mpls-mna-hdr-12>.

   [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,
              <https://datatracker.ietf.org/doc/html/draft-ietf-mpls-
              mna-usecases-15>.

   [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,
              <https://ieeexplore.ieee.org/document/10947349>.

   [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, <https://www.rfc-editor.org/rfc/rfc7684>.

   [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, <https://www.rfc-editor.org/rfc/rfc7684>.

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   [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, <https://www.rfc-editor.org/rfc/rfc7770>.

   [rfc7981]  Ginsberg, L., Previdi, S., and M. Chen, "IS-IS Extensions
              for Advertising Router Information", RFC 7981,
              DOI 10.17487/RFC7981, October 2016,
              <https://www.rfc-editor.org/rfc/rfc7981>.

   [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, <https://www.rfc-editor.org/rfc/rfc8362>.

   [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, <https://www.rfc-editor.org/rfc/rfc8362>.

   [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,
              <https://www.rfc-editor.org/rfc/rfc8476>.

   [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,
              <https://www.rfc-editor.org/rfc/rfc8491>.

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

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   Michael Menth
   University of Tuebingen
   Tuebingen
   Germany
   Email: michael.menth@uni-tuebingen.de

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