



Internet Engineering Task Force (IETF)                       P. Kaneriya
Request for Comments: 9885                                         T. Li
Category: Standards Track                                  A. Przygienda
ISSN: 2070-1721                                                 S. Hegde
                                                        Juniper Networks
                                                             L. Ginsberg
                                                           Cisco Systems
                                                            October 2025


                        Multi-Part TLVs in IS-IS

Abstract

   New technologies are adding new information into IS-IS while
   deployment scales are simultaneously increasing.  This causes the
   contents of many critical TLVs to exceed the currently supported
   limit of 255 octets.  This document codifies the common mechanism of
   extending the TLV content space through multiple TLVs.

Status of This Memo

   This is an Internet Standards Track document.

   This document is a product of the Internet Engineering Task Force
   (IETF).  It represents the consensus of the IETF community.  It has
   received public review and has been approved for publication by the
   Internet Engineering Steering Group (IESG).  Further information on
   Internet Standards is available in Section 2 of RFC 7841.

   Information about the current status of this document, any errata,
   and how to provide feedback on it may be obtained at
   https://www.rfc-editor.org/info/rfc9885.

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
   2.  Requirements Language
   3.  Overview of MP-TLV Applicability to TLVs
     3.1.  TLVs that Advertise a List of Objects
     3.2.  TLVs that Advertise Objects with Identifier(s)
       3.2.1.  Example: Extended IS Reachability
       3.2.2.  Example: Extended IP Reachability
   4.  Multi-Part TLVs
   5.  Procedure for Receiving Multi-Part TLVs
   6.  Specification of Applicability of Multi-Part TLVs
   7.  MP-TLV Capability Advertisement
   8.  Deployment Considerations
     8.1.  Controls and Alarms
     8.2.  Restrictions on Generation of MP-TLVs
   9.  IANA Considerations
     9.1.  MP-TLV Support Sub-TLV
     9.2.  Extension to IS-IS Top-Level TLV Registries
       9.2.1.  MP-TLV for IS-IS Top-Level TLV Codepoints
       9.2.2.  MP-TLV for IS-IS Sub-TLVs for Reverse Metric TLV
       9.2.3.  MP-TLV for IS-IS Sub-TLVs for TLVs Advertising Neighbor
               Information
       9.2.4.  MP-TLV for IS-IS Sub-TLVs for TLVs Advertising Prefix
               Reachability
       9.2.5.  MP-TLV for IS-IS Sub-TLVs for MT-Capability TLV
       9.2.6.  MP-TLV for IS-IS Sub-TLVs for IS-IS Router CAPABILITY
               TLV
       9.2.7.  IS-IS Sub-Sub-TLVs for SRv6 Capabilities Sub-TLV
       9.2.8.  MP-TLV IS-IS Sub-Sub-TLVs for BIER Info Sub-TLV
       9.2.9.  MP-TLV for IS-IS Sub-TLVs for Segment Identifier/Label
               Binding TLVs
       9.2.10. MP-TLV for IS-IS Sub-Sub-TLV Codepoints for
               Application-Specific Link Attributes
       9.2.11. MP-TLV for IS-IS Sub-TLVs for Application-Specific SRLG
               TLV
       9.2.12. MP-TLV for IS-IS Sub-Sub-TLVs for SRv6 SID Sub-TLVs
       9.2.13. MP-TLV for IS-IS Sub-Sub-TLVs for Flexible Algorithm
               Definition Sub-TLV
       9.2.14. MP-TLV for IS-IS Sub-Sub-TLVs for Flood Reflection
               Discovery Sub-TLV
   10. Security Considerations
   11. References
     11.1.  Normative References
     11.2.  Informative References
   Contributors
   Authors' Addresses

1.  Introduction

   The continued growth of the Internet has resulted in a commensurate
   growth in the scale of service provider networks and the amount of
   information carried in IS-IS [ISO10589] Type-Length-Value (TLV)
   tuples.  Simultaneously, new traffic engineering technologies are
   defining new attributes, further adding to the scaling pressures.
   The original TLV definition limits each TLV to a maximum of 255
   octets of payload, which is becoming increasingly problematic.

   Some TLV definitions have addressed this by explicitly stating that a
   TLV may appear multiple times inside of a Link State PDU (LSP).
   However, this has not been done for many currently defined TLVs,
   leaving the situation somewhat ambiguous.

   For example, [RFC5305] defines the Extended IS reachability TLV (22)
   and [RFC5120] defines the MT-ISN TLV (222).  These documents do not
   specify sending multiple TLVs for the same object and no other
   mechanism for expanding the information carrying capacity of the TLV
   has been specified.

   The intent of this document is to clarify and codify the situation by
   explicitly making multiple occurrences of a TLV the standard
   mechanism for scaling TLV contents.  Any future document that
   proposes a different mechanism for scaling TLV contents for a given
   codepoint must explain why multiple occurrences of a TLV is not
   appropriate.

   This document does not alter the encoding of any TLV where multiple
   occurrences of a TLV are already defined.  Some examples of this are:

   *  Router CAPABILITY TLV (Type 242) [RFC7981]

   *  Application-Specific SRLG (Type 238) [RFC9479]

   *  Instance Identifier (Type 7) [RFC8202]

   *  Application-Specific Link Attributes (sub-TLV Type 16) [RFC9479]

   [RFC7356] has defined a 16-bit Length field for TLVs in flooding
   scoped Protocol Data Units (PDUs).  The problem addressed by this
   document would likely not be encountered when 16-bit Length TLVs are
   in use.  However, introduction of these new PDU types is not
   backwards compatible.  Therefore, there is a need to address how to
   expand the information advertised in existing PDUs that use TLVs with
   8-bit length fields.

   The mechanism described in this document has not been documented for
   all TLVs previously.  This document provides the necessary protocol
   definition and discusses potential interoperability issues and
   deployment challenges.

   This document specifies a means for extending TLVs where no extension
   mechanism has been previously explicitly specified.  It also
   specifies this mechanism as the default extension mechanism for
   future TLVs.  The mechanism described in this document is applicable
   to top level TLVs as well as any level of sub-TLVs that may appear
   within a top level TLV.

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.  Overview of MP-TLV Applicability to TLVs

   A TLV is a tuple of (Type, Length, Value) and can be advertised in
   IS-IS packets.  Both Type and Length fields are one octet in size,
   which leads to the limitation that a maximum of 255 octets can be
   sent in a single TLV.  TLVs that have certain general characteristics
   have the potential to require advertisement of more than 255 octets.
   These generic types are described in more detail in the following
   subsections.

3.1.  TLVs that Advertise a List of Objects

   Some TLVs are simply a list of objects of a given type.  For example,
   the BFD-Enabled TLV (Type 148) [RFC6213] contains a list of Multi-
   Topology Identifier (MTID)/ Network Layer Protocol Identifier (NLPID)
   pairs.  If more than 255 octets are required to advertise all of the
   MTID/NLPID pairs, multiple BFD-Enabled TLVs would be required.  The
   relationship between multiple BFD-Enabled TLVs is established using
   the TLV type.

3.2.  TLVs that Advertise Objects with Identifier(s)

   Some TLVs support advertisement of objects of a given type, where
   each object is identified by a unique set of identifiers.  In this
   case, the "key" that uniquely identifies a given object consists of
   the set of identifiers.

3.2.1.  Example: Extended IS Reachability

   As an example, consider the Extended IS reachability TLV (Type 22)
   [RFC5305].  A neighbor in this TLV is specified by:

   *  7 octets of a system ID and pseudonode number

   *  3 octets of a default metric

   *  Optionally, one or more of the following link identifiers encoded
      as sub-TLVs:

      -  an IPv4 interface address and IPv4 neighbor address as
         specified in [RFC5305]

      -  an IPv6 interface address and IPv6 neighbor address as
         specified in [RFC6119]

      -  Link Local/Remote Identifiers as specified in [RFC5307]

   The key consists of the 7 octets of system ID and pseudonode number
   plus the set of link identifiers that are present.

3.2.2.  Example: Extended IP Reachability

   As another example, consider the Extended IP reachability TLV (Type
   135) [RFC5305].  A prefix in this TLV is specified by:

   *  4 octets of metric information

   *  1 octet of control information that includes 6 bits specifying the
      prefix length

   *  0-4 octets of an IPv4 prefix

   The above are followed by up to 250 octets of sub-TLV information.

   The key consists of the 6 bits of prefix length plus 0-4 octets of an
   IPv4 prefix.

4.  Multi-Part TLVs

   If a router advertises multiple TLV tuples with the same TLV type and
   the same key (when applicable) in an IS-IS Hello (IIH) packet or in
   the set of LSPs for a given level, they are considered a Multi-Part
   TLV (MP-TLV).

   In the absence of MP-TLV support, when a router receives an MP-TLV,
   the receiver chooses which TLV will be processed and which TLV will
   be ignored.  Note that this can occur either legitimately as a
   transient condition when a TLV moves from one LSP to another or as a
   result of a defect in the sending implementation.

   In the presence of MP-TLV support, when a router receives an MP-TLV,
   information from all the TLVs is processed.

   The encoding of TLVs is not altered by the introduction of MP-TLV
   support.  In particular, the "key" that is used to identify the set
   of TLVs that form an MP-TLV is the same key used in the absence of
   MP-TLV support.  Also note the definition of the "key" is part of the
   specification(s) that define(s) the TLV and is therefore outside the
   scope of this document.

   NOTE: This document intentionally does not include a definition of
   the key for each codepoint.  To do so would be redundant and risk
   unintentionally deviating from the definition that already exists in
   the relevant specifications.  Also, the term "key" is a generic term
   that is not used in the relevant specifications.

   Each TLV that is part of an MP-TLV MUST be parsable independent of
   other TLVs in the MP-TLV.  Breaking of a single sub-TLV or other data
   unit across TLVs MUST NOT be done.  Breaking of a data unit across
   TLVs results in an invalid encoding.  Guidelines to receivers for
   handling such a case are specified in [RFC8918].

5.  Procedure for Receiving Multi-Part TLVs

   A router that receives an MP-TLV MUST accept all of the information
   in all of the parts.  The order of arrival and placement of the TLV
   parts in LSP fragments is irrelevant.  Multiple TLV parts MAY occur
   in a single LSP or parts MAY occur in different LSPs.

   The placement of the TLV parts in an IIH is irrelevant.

   When processing MP-TLVs, implementations MUST NOT impose a minimum
   length check.  Although MP-TLVs SHOULD NOT be sent unless the
   capacity of a single TLV (255 octets) is exceeded, receivers MUST NOT
   reject MP-TLVs if senders do not strictly adhere to this constraint.
   For example, if two MP-TLVs are received, each of which has a length
   of 100 bytes, the fact that the total amount of data does not exceed
   255 bytes MUST NOT cause the TLVs to be rejected.  See Section 8.2
   for guidance on sending MP-TLVs.

   The contents of an MP-TLV MUST be processed as if they were
   concatenated.  If the internals of the TLV contain key information,
   then replication of the key information MUST be taken to indicate
   that subsequent data MUST be processed as if the subsequent data were
   concatenated after a single copy of the key information.

   For example, suppose that a router receives an LSP with a Multi-Part
   Extended IS reachability TLV.  The first part contains key
   information K with unique sub-TLVs A, B, and C.  The second part
   contains key information K with unique sub-TLVs D, E, and F.  The
   receiving router must then process this as having key information K
   and unique sub-TLVs A, B, C, D, E, F, or, because ordering is
   irrelevant, unique sub-TLVs D, E, F, A, B, C, or any other
   permutation.

   A TLV may contain information in its fixed part that is not part of
   the key.  For example, the metric in both the Extended IS
   reachability TLV and the Extended IP Reachability TLV does not
   specify which object the TLV refers to, and thus is not part of the
   key.  Having inconsistent information in different parts of an MP-TLV
   is an error.

   It is also possible that information that is not part of the fixed
   part of a TLV can be duplicated, e.g., a sub-TLV that is intended to
   only appear once appears multiple times and has inconsistent values.
   This could occur within the same TLV or in different parts of an MP-
   TLV.  This is also an error.

   The document defining the TLV should specify how to handle such
   cases.  If such a document is not explicit in how to handle such
   cases, the following procedure is defined:

   *  The first occurrence in the lowest numbered LSP is used.
      Subsequent occurrences in the same LSP or higher numbered LSPs are
      ignored.

   *  In the case of IIHs, the first occurrence in the IIH is used.
      Subsequent occurrences in the IIH are ignored.

6.  Specification of Applicability of Multi-Part TLVs

   As mentioned in Section 1, existing specifications for some TLVs have
   explicitly stated that the use of MP-TLV procedures are applicable to
   that codepoint.  However, MP-TLV procedures are potentially
   applicable to any codepoint that allows sub-TLVs to be included as
   part of the information advertised.  MP-TLV procedures may also be
   applicable to codepoints that do not support sub-TLVs, but which
   define an unbounded number of attributes that may be advertised
   within a single codepoint.  An example of the latter is GMPLS-SRLG as
   defined in [RFC5307].

   The lack of explicit indication of applicability of MP-TLV procedures
   for all codepoints to which such procedures could be applied
   contributes to potential interoperability problems if/when there is
   need to advertise more than 255 octets of information for such a
   codepoint.

   This document makes explicit the applicability of MP-TLV procedures
   for all existing codepoints defined for the IS-IS protocol by
   extending existing and relevant IANA protocol registries to include
   an explicit indication of applicability of MP-TLV procedures for each
   codepoint.  See Section 9.  Therefore, any new codepoints defined by
   future protocol extensions will explicitly indicate the applicability
   of MP-TLV procedures to the new codepoints.

7.  MP-TLV Capability Advertisement

   Introduction of the use of MP-TLV for codepoints where the existing
   specifications have not explicitly defined MP-TLV support can be
   extremely disruptive to network operations in cases where not all
   routers in the network support MP-TLV for those codepoints.  Partial
   deployment can easily result in traffic loss and/or other unexpected
   behaviors that may be hard to diagnose.

   For example, if there are multiple TLVs associated with the
   advertisement of a neighbor and an implementation does not process
   all of the link attributes advertised, then constrained path
   calculations based on those attributes are likely to produce
   incorrect or unexpected results.  This could produce forwarding loops
   or dropped traffic.

   As an aid to network operators when diagnosing such situations, a new
   sub-TLV of the IS-IS Router CAPABILITY TLV [RFC7981] is defined:

   MP-TLV Support for TLVs with Implicit Support

   Type:  30 (1 octet)
   Length:  0 (1 octet)

   Routers that support MP-TLV for codepoints for which existing
   specifications do not explicitly define such support, but for which
   MP-TLV is applicable, SHOULD include this sub-TLV in a Router
   CAPABILITY TLV.

   Scope of the associated Router CAPABILITY TLV is per level (S-bit
   clear) [RFC7981].

   This advertisement is for informational purposes only.  IS-IS
   protocol implementations MUST NOT alter what is sent or how what is
   received is processed based on these advertisements.

   The sub-TLV intentionally does not provide a syntax to specify MP-TLV
   support on a per-codepoint basis.  It is presumed that if such
   support is provided that it applies to all relevant codepoints.  It
   is understood that in reality, a given implementation might limit MP-
   TLV support to particular codepoints based on the needs of the
   deployment scenarios in which it is used.  Therefore, diligence is
   still required on the part of the operator to ensure that
   configurations which require the sending of an MP-TLV for a given
   codepoint are not introduced on any router in the network until all
   routers in the network support MP-TLV for the relevant codepoints.

   The Router CAPABILITY TLV is meant to advertise capabilities that are
   of direct use to the IS-IS protocol.  The MP-TLV Support sub-TLV
   advertises management information, which is not of direct use to the
   protocol.  The intent is to provide information that may be of use to
   a network operator.  This exception to the intended use of the Router
   CAPABILITY TLV is introduced to help mitigate the potential
   disruptiveness associated with the introduction of MP-TLV support in
   cases where such support has not been explicitly defined.  This is
   not intended to introduce a generic new use case for the Router
   CAPABILITY TLV.

   NOTE: A more appropriate and robust mechanism to provide detailed
   information on what a given implementation supports is to utilize
   YANG to define Protocol Implementation Conformance Statement (PICS).
   An example of this can be found in [PICS-YANG].

8.  Deployment Considerations

   Sending of MP-TLVs in the presence of routers that do not correctly
   process such advertisements can result in interoperability issues,
   including incorrect forwarding of packets.  This section discusses
   best practices to be used when a deployment requires the use of MP-
   TLVs for codepoints for which existing specifications do not
   explicitly indicate MP-TLV support.

   While it is not in scope for this document to mandate how
   implementations provide the means to prevent (or at least make less
   likely) partial deployment of MP-TLV for a given codepoint, it is
   important to emphasize the need to assist operators in avoiding
   inadvertent problematic deployment scenarios.  Providing appropriate
   controls to enable/disable the sending of MP-TLVs as discussed in
   Section 8.1 is important to avoid interoperability issues.

8.1.  Controls and Alarms

   It is RECOMMENDED that implementations that support the sending of
   MP-TLVs provide configuration controls that enable/disable generation
   of MP-TLVs.  Given that MP-TLV support in a given implementation may
   vary on a per-TLV basis, these controls SHOULD provide support at a
   per-codepoint granularity.  For example, an implementation might
   support MP-TLVs for IS Extended Reachability but not for IP
   Reachability.

   Implementations that support disablement of MP-TLVs MUST log the
   following occurrences:

   *  An MP-TLV is received when use of MP-TLVs is disabled.

   *  Local LSP generation requires the use of MP-TLVs when generation
      of MP-TLVs is disabled.

   Network operators SHOULD NOT enable MP-TLVs until ensuring that all
   implementations that will receive the MP-TLVs are capable of
   interpreting them correctly as described in Section 5.

8.2.  Restrictions on Generation of MP-TLVs

   This section discusses restrictions on sending of MP-TLVs.  When
   applying these restrictions, it is assumed that it has already been
   determined that sending of MP-TLVs is allowed based on the setting of
   the controls discussed in Section 8.1.

   Sending a single TLV with all the information about an object is
   preferable to sending multiple TLVs.  It is simpler and more
   efficient to parse information from a single TLV than to combine the
   information from multiple TLVs.  Implementations SHOULD NOT send
   multiple TLVs unless MP-TLV is applicable to the TLV and the amount
   of information that is required to be sent exceeds the capacity of a
   single TLV.  For example, when additional space is required in an
   existing TLV, as long as there is space in the TLV, information
   SHOULD NOT be split into multiple TLVs.  If there is no space in the
   current LSP to fit the now larger TLV, the TLV SHOULD be moved to a
   new LSP.

9.  IANA Considerations

9.1.  MP-TLV Support Sub-TLV

   IANA has registered the following codepoint from the "IS-IS Sub-TLVs
   for IS-IS Router CAPABILITY TLV" registry (see
   <https://www.iana.org/assignments/isis-tlv-codepoints>):

   Type:  30
   Description:  MP-TLV Support for TLVs with Implicit Support
   MP-TLV Applicability:  N
   Reference:  Section 7 of RFC 9885

9.2.  Extension to IS-IS Top-Level TLV Registries

   IANA has extended a number of registries within the "IS-IS TLV
   Codepoints" registry group to include a column that indicates whether
   the MP-TLV procedures described in this document are applicable to
   that codepoint.  "Y" indicates that MP-TLV is applicable.  "N"
   indicates MP-TLV is not applicable.

   The following subsections provide the initial contents of the new
   column for a number of existing registries.  The initial values for
   MP-TLV applicability defined in the following subsections are based
   on the rule that MP-TLV is applicable to any codepoint that supports
   sub-TLVs, without regard to whether the sub-TLVs that are currently
   defined are sufficient to require MP-TLVs to be sent.

   To access the relevant IANA registry, search for the registry name
   associated with each subsection at <https://www.iana.org/assignments/
   isis-tlv-codepoints>.

9.2.1.  MP-TLV for IS-IS Top-Level TLV Codepoints

   IANA has added the MP column to the "IS-IS Top-Level TLV Codepoints"
   registry and populated it as shown in Table 1.

          +===========+====================================+====+
          | Value     | Name                               | MP |
          +===========+====================================+====+
          | 0         | Reserved                           |    |
          +-----------+------------------------------------+----+
          | 1         | Area Addresses                     | N  |
          +-----------+------------------------------------+----+
          | 2         | IIS Neighbors                      | N  |
          +-----------+------------------------------------+----+
          | 3         | ES Neighbors                       | N  |
          +-----------+------------------------------------+----+
          | 4         | Part. DIS                          | N  |
          +-----------+------------------------------------+----+
          | 5         | Prefix Neighbors                   | N  |
          +-----------+------------------------------------+----+
          | 6         | IIS Neighbors                      | N  |
          +-----------+------------------------------------+----+
          | 7         | Instance Identifier                | Y  |
          +-----------+------------------------------------+----+
          | 8         | Padding                            | N  |
          +-----------+------------------------------------+----+
          | 9         | LSP Entries                        | N  |
          +-----------+------------------------------------+----+
          | 10        | Authentication                     | N  |
          +-----------+------------------------------------+----+
          | 11        | ESN TLV                            | N  |
          +-----------+------------------------------------+----+
          | 12        | Opt. Checksum                      | N  |
          +-----------+------------------------------------+----+
          | 13        | Purge Originator Identification    | N  |
          +-----------+------------------------------------+----+
          | 14        | LSPBufferSize                      | N  |
          +-----------+------------------------------------+----+
          | 15        | Router-Fingerprint                 | N  |
          +-----------+------------------------------------+----+
          | 16        | Reverse Metric                     | N  |
          +-----------+------------------------------------+----+
          | 17        | IS-IS Area Node IDs TLV            | N  |
          +-----------+------------------------------------+----+
          | 18        | IS-IS Flooding Path TLV            | N  |
          +-----------+------------------------------------+----+
          | 19        | IS-IS Flooding Request TLV         | N  |
          +-----------+------------------------------------+----+
          | 20        | Area Proxy                         | Y  |
          +-----------+------------------------------------+----+
          | 21        | Flooding Parameters TLV            | Y  |
          +-----------+------------------------------------+----+
          | 22        | Extended IS reachability           | Y  |
          +-----------+------------------------------------+----+
          | 23        | IS Neighbor Attribute              | Y  |
          +-----------+------------------------------------+----+
          | 24        | IS Alias ID                        | N  |
          +-----------+------------------------------------+----+
          | 25        | L2 Bundle Member Attributes        | Y  |
          +-----------+------------------------------------+----+
          | 26        | Unassigned                         |    |
          +-----------+------------------------------------+----+
          | 27        | SRv6 Locator                       | Y  |
          +-----------+------------------------------------+----+
          | 28-41     | Unassigned                         |    |
          +-----------+------------------------------------+----+
          | 42        | DECnet Phase IV                    | N  |
          +-----------+------------------------------------+----+
          | 43-65     | Unassigned                         |    |
          +-----------+------------------------------------+----+
          | 66        | Lucent Proprietary                 | N  |
          +-----------+------------------------------------+----+
          | 67-125    | Unassigned                         |    |
          +-----------+------------------------------------+----+
          | 126       | IPv4 Algorithm Prefix Reachability | N  |
          +-----------+------------------------------------+----+
          | 127       | IPv6 Algorithm Prefix Reachability | N  |
          +-----------+------------------------------------+----+
          | 128       | IP Int. Reach                      | N  |
          +-----------+------------------------------------+----+
          | 129       | Prot. Supported                    | N  |
          +-----------+------------------------------------+----+
          | 130       | IP Ext. Address                    | N  |
          +-----------+------------------------------------+----+
          | 131       | IDRPI                              | N  |
          +-----------+------------------------------------+----+
          | 132       | IP Intf. Address                   | N  |
          +-----------+------------------------------------+----+
          | 133       | Illegal                            | N  |
          +-----------+------------------------------------+----+
          | 134       | Traffic Engineering router ID      | N  |
          +-----------+------------------------------------+----+
          | 135       | Extended IP reachability           | Y  |
          +-----------+------------------------------------+----+
          | 136       | Unassigned                         |    |
          +-----------+------------------------------------+----+
          | 137       | Dynamic Name                       | N  |
          +-----------+------------------------------------+----+
          | 138       | GMPLS-SRLG                         | Y  |
          +-----------+------------------------------------+----+
          | 139       | IPv6 SRLG                          | N  |
          +-----------+------------------------------------+----+
          | 140       | IPv6 TE Router ID                  | N  |
          +-----------+------------------------------------+----+
          | 141       | inter-AS reachability information  | Y  |
          +-----------+------------------------------------+----+
          | 142       | GADDR-TLV                          | Y  |
          +-----------+------------------------------------+----+
          | 143       | MT-Port-Cap-TLV                    | Y  |
          +-----------+------------------------------------+----+
          | 144       | MT-Capability TLV                  | Y  |
          +-----------+------------------------------------+----+
          | 145       | TRILL Neighbor TLV                 | N  |
          +-----------+------------------------------------+----+
          | 146       | Unassigned                         |    |
          +-----------+------------------------------------+----+
          | 147       | MAC-RI TLV                         | Y  |
          +-----------+------------------------------------+----+
          | 148       | BFD-Enabled TLV                    | Y  |
          +-----------+------------------------------------+----+
          | 149       | Segment Identifier / Label Binding | Y  |
          +-----------+------------------------------------+----+
          | 150       | Multi-Topology Segment Identifier  | Y  |
          |           | / Label Binding                    |    |
          +-----------+------------------------------------+----+
          | 151-160   | Unassigned                         |    |
          +-----------+------------------------------------+----+
          | 161       | Flood Reflection                   | N  |
          +-----------+------------------------------------+----+
          | 162-175   | Unassigned                         |    |
          +-----------+------------------------------------+----+
          | 176       | Nortel Proprietary                 | N  |
          +-----------+------------------------------------+----+
          | 177       | Nortel Proprietary                 | N  |
          +-----------+------------------------------------+----+
          | 178-210   | Unassigned                         |    |
          +-----------+------------------------------------+----+
          | 211       | Restart TLV                        | N  |
          +-----------+------------------------------------+----+
          | 212-221   | Unassigned                         |    |
          +-----------+------------------------------------+----+
          | 222       | MT-ISN                             | Y  |
          +-----------+------------------------------------+----+
          | 223       | MT IS Neighbor Attribute           | Y  |
          +-----------+------------------------------------+----+
          | 224-228   | Unassigned                         |    |
          +-----------+------------------------------------+----+
          | 229       | M-Topologies                       | N  |
          +-----------+------------------------------------+----+
          | 230-231   | Unassigned                         |    |
          +-----------+------------------------------------+----+
          | 232       | IPv6 Intf. Addr.                   | N  |
          +-----------+------------------------------------+----+
          | 233       | IPv6 Global Interface Address TLV  | N  |
          +-----------+------------------------------------+----+
          | 234       | Unassigned                         |    |
          +-----------+------------------------------------+----+
          | 235       | MT IP. Reach                       | Y  |
          +-----------+------------------------------------+----+
          | 236       | IPv6 IP. Reach                     | Y  |
          +-----------+------------------------------------+----+
          | 237       | MT IPv6 IP. Reach                  | Y  |
          +-----------+------------------------------------+----+
          | 238       | Application-Specific SRLG          | Y  |
          +-----------+------------------------------------+----+
          | 239       | Unassigned                         |    |
          +-----------+------------------------------------+----+
          | 240       | P2P 3-Way Adj. State               | N  |
          +-----------+------------------------------------+----+
          | 241       | Unassigned                         |    |
          +-----------+------------------------------------+----+
          | 242       | IS-IS Router CAPABILITY TLV        | Y  |
          +-----------+------------------------------------+----+
          | 243       | Scope Flooding Support             | N  |
          +-----------+------------------------------------+----+
          | 244-250   | Unassigned                         |    |
          +-----------+------------------------------------+----+
          | 251       | Generic Information                | Y  |
          +-----------+------------------------------------+----+
          | 252-65535 | Unassigned                         |    |
          +-----------+------------------------------------+----+

                  Table 1: IS-IS Top-Level TLV Codepoints

9.2.2.  MP-TLV for IS-IS Sub-TLVs for Reverse Metric TLV

   IANA has added the MP column to the "IS-IS Sub-TLVs for Reverse
   Metric TLV" registry and populated it as shown in Table 2.

               +========+============================+====+
               | Value  | Name                       | MP |
               +========+============================+====+
               | 0      | Reserved                   |    |
               +--------+----------------------------+----+
               | 1-17   | Unassigned                 |    |
               +--------+----------------------------+----+
               | 18     | Traffic Engineering Metric | N  |
               +--------+----------------------------+----+
               | 19-255 | Unassigned                 |    |
               +--------+----------------------------+----+

                   Table 2: IS-IS Sub-TLVs for Reverse
                                Metric TLV

9.2.3.  MP-TLV for IS-IS Sub-TLVs for TLVs Advertising Neighbor
        Information

   IANA has added the MP column to the "IS-IS Sub-TLVs for TLVs
   Advertising Neighbor Information" registry and populated it as shown
   in Table 3.

   +=========+===================================================+====+
   | Value   | Name                                              | MP |
   +=========+===================================================+====+
   | 0-2     | Unassigned                                        |    |
   +---------+---------------------------------------------------+----+
   | 3       | Administrative group (color)                      | N  |
   +---------+---------------------------------------------------+----+
   | 4       | Link Local/Remote Identifiers                     | N  |
   +---------+---------------------------------------------------+----+
   | 5       | Unassigned                                        |    |
   +---------+---------------------------------------------------+----+
   | 6       | IPv4 interface address                            | N  |
   +---------+---------------------------------------------------+----+
   | 7       | Unassigned                                        |    |
   +---------+---------------------------------------------------+----+
   | 8       | IPv4 neighbor address                             | N  |
   +---------+---------------------------------------------------+----+
   | 9       | Maximum link bandwidth                            | N  |
   +---------+---------------------------------------------------+----+
   | 10      | Maximum reservable link bandwidth                 | N  |
   +---------+---------------------------------------------------+----+
   | 11      | Unreserved bandwidth                              | N  |
   +---------+---------------------------------------------------+----+
   | 12      | IPv6 Interface Address                            | N  |
   +---------+---------------------------------------------------+----+
   | 13      | IPv6 Neighbor Address                             | N  |
   +---------+---------------------------------------------------+----+
   | 14      | Extended Administrative Group                     | N  |
   +---------+---------------------------------------------------+----+
   | 15      | Link MSD                                          | Y  |
   +---------+---------------------------------------------------+----+
   | 16      | Application-Specific Link Attributes              | Y  |
   +---------+---------------------------------------------------+----+
   | 17      | Generic Metric                                    | N  |
   +---------+---------------------------------------------------+----+
   | 18      | TE Default metric                                 | N  |
   +---------+---------------------------------------------------+----+
   | 19      | Link-attributes                                   | N  |
   +---------+---------------------------------------------------+----+
   | 20      | Link Protection Type                              | N  |
   +---------+---------------------------------------------------+----+
   | 21      | Interface Switching Capability Descriptor         | Y  |
   +---------+---------------------------------------------------+----+
   | 22      | Bandwidth Constraints                             | N  |
   +---------+---------------------------------------------------+----+
   | 23      | Unconstrained TE LSP Count (sub-)TLV              | N  |
   +---------+---------------------------------------------------+----+
   | 24      | Remote AS Number                                  | N  |
   +---------+---------------------------------------------------+----+
   | 25      | IPv4 Remote ASBR Identifier                       | N  |
   +---------+---------------------------------------------------+----+
   | 26      | IPv6 Remote ASBR Identifier                       | N  |
   +---------+---------------------------------------------------+----+
   | 27      | Interface Adjustment Capability Descriptor (IACD) | Y  |
   +---------+---------------------------------------------------+----+
   | 28      | MTU                                               | N  |
   +---------+---------------------------------------------------+----+
   | 29      | SPB-Metric                                        | N  |
   +---------+---------------------------------------------------+----+
   | 30      | SPB-A-OALG                                        | Y  |
   +---------+---------------------------------------------------+----+
   | 31      | Adjacency Segment Identifier                      | N  |
   +---------+---------------------------------------------------+----+
   | 32      | LAN Adjacency Segment Identifier                  | N  |
   +---------+---------------------------------------------------+----+
   | 33      | Unidirectional Link Delay                         | N  |
   +---------+---------------------------------------------------+----+
   | 34      | Min/Max Unidirectional Link Delay                 | N  |
   +---------+---------------------------------------------------+----+
   | 35      | Unidirectional Delay Variation                    | N  |
   +---------+---------------------------------------------------+----+
   | 36      | Unidirectional Link Loss                          | N  |
   +---------+---------------------------------------------------+----+
   | 37      | Unidirectional Residual Bandwidth                 | N  |
   +---------+---------------------------------------------------+----+
   | 38      | Unidirectional Available Bandwidth                | N  |
   +---------+---------------------------------------------------+----+
   | 39      | Unidirectional Utilized Bandwidth                 | N  |
   +---------+---------------------------------------------------+----+
   | 40      | RTM Capability                                    | N  |
   +---------+---------------------------------------------------+----+
   | 41      | L2 Bundle Member Adj-SID                          | Y  |
   +---------+---------------------------------------------------+----+
   | 42      | L2 Bundle Member LAN Adj-SID                      | Y  |
   +---------+---------------------------------------------------+----+
   | 43      | SRv6 End.X SID                                    | Y  |
   +---------+---------------------------------------------------+----+
   | 44      | SRv6 LAN End.X SID                                | Y  |
   +---------+---------------------------------------------------+----+
   | 45      | IPv6 Local ASBR Identifier                        | N  |
   +---------+---------------------------------------------------+----+
   | 46-160  | Unassigned                                        |    |
   +---------+---------------------------------------------------+----+
   | 161     | Flood Reflector Adjacency                         | N  |
   +---------+---------------------------------------------------+----+
   | 162-249 | Unassigned                                        |    |
   +---------+---------------------------------------------------+----+
   | 250-254 | Reserved for Cisco-specific extensions            |    |
   +---------+---------------------------------------------------+----+
   | 255     | Reserved for future expansion                     |    |
   +---------+---------------------------------------------------+----+

    Table 3: IS-IS Sub-TLVs for TLVs Advertising Neighbor Information

9.2.4.  MP-TLV for IS-IS Sub-TLVs for TLVs Advertising Prefix
        Reachability

   IANA has added the MP column to the "IS-IS Sub-TLVs for TLVs
   Advertising Prefix Reachability" registry and populated it as shown
   in Table 4.

         +========+=========================================+====+
         | Value  | Name                                    | MP |
         +========+=========================================+====+
         | 0      | Unassigned                              |    |
         +--------+-----------------------------------------+----+
         | 1      | 32-bit Administrative Tag Sub-TLV       | Y  |
         +--------+-----------------------------------------+----+
         | 2      | 64-bit Administrative Tag Sub-TLV       | Y  |
         +--------+-----------------------------------------+----+
         | 3      | Prefix Segment Identifier               | N  |
         +--------+-----------------------------------------+----+
         | 4      | Prefix Attribute Flags                  | N  |
         +--------+-----------------------------------------+----+
         | 5      | SRv6 End SID                            | Y  |
         +--------+-----------------------------------------+----+
         | 6      | Flexible Algorithm Prefix Metric (FAPM) | N  |
         +--------+-----------------------------------------+----+
         | 7-10   | Unassigned                              |    |
         +--------+-----------------------------------------+----+
         | 11     | IPv4 Source Router ID                   | N  |
         +--------+-----------------------------------------+----+
         | 12     | IPv6 Source Router ID                   | N  |
         +--------+-----------------------------------------+----+
         | 13-31  | Unassigned                              |    |
         +--------+-----------------------------------------+----+
         | 32     | BIER Info                               | Y  |
         +--------+-----------------------------------------+----+
         | 33-255 | Unassigned                              |    |
         +--------+-----------------------------------------+----+

            Table 4: IS-IS Sub-TLVs for TLVs Advertising Prefix
                                Reachability

9.2.5.  MP-TLV for IS-IS Sub-TLVs for MT-Capability TLV

   IANA has added the MP column to the "IS-IS Sub-TLVs for MT-Capability
   TLV" registry and populated it as shown in Table 5.

              +========+==============================+====+
              | Value  | Name                         | MP |
              +========+==============================+====+
              | 0      | Reserved                     |    |
              +--------+------------------------------+----+
              | 1      | SPB-Inst                     | N  |
              +--------+------------------------------+----+
              | 2      | SPB-I-OALG                   | Y  |
              +--------+------------------------------+----+
              | 3      | SPBM-SI                      | Y  |
              +--------+------------------------------+----+
              | 4      | SPBV-ADDR                    | Y  |
              +--------+------------------------------+----+
              | 5      | Unassigned                   |    |
              +--------+------------------------------+----+
              | 6      | NICKNAME                     | Y  |
              +--------+------------------------------+----+
              | 7      | TREES                        | N  |
              +--------+------------------------------+----+
              | 8      | TREE-RT-IDs                  | Y  |
              +--------+------------------------------+----+
              | 9      | TREE-USE-IDs                 | Y  |
              +--------+------------------------------+----+
              | 10     | INT-VLAN                     | Y  |
              +--------+------------------------------+----+
              | 11-12  | Unassigned                   |    |
              +--------+------------------------------+----+
              | 13     | TRILL-VER                    | N  |
              +--------+------------------------------+----+
              | 14     | VLAN-GROUP                   | Y  |
              +--------+------------------------------+----+
              | 15     | INT-LABEL                    | Y  |
              +--------+------------------------------+----+
              | 16     | RBCHANNELS                   | Y  |
              +--------+------------------------------+----+
              | 17     | AFFINITY                     | Y  |
              +--------+------------------------------+----+
              | 18     | LABEL-GROUP                  | Y  |
              +--------+------------------------------+----+
              | 19-20  | Unassigned                   |    |
              +--------+------------------------------+----+
              | 21     | Topology sub-TLV             | Y  |
              +--------+------------------------------+----+
              | 22     | Hop sub-TLV                  | N  |
              +--------+------------------------------+----+
              | 23     | Bandwidth Constraint sub-TLV | N  |
              +--------+------------------------------+----+
              | 24     | Bandwidth Assignment sub-TLV | N  |
              +--------+------------------------------+----+
              | 25     | Timestamp sub-TLV            | N  |
              +--------+------------------------------+----+
              | 26-254 | Unassigned                   |    |
              +--------+------------------------------+----+
              | 255    | Reserved                     |    |
              +--------+------------------------------+----+

              Table 5: IS-IS Sub-TLVs for MT-Capability TLV

9.2.6.  MP-TLV for IS-IS Sub-TLVs for IS-IS Router CAPABILITY TLV

   IANA has added the MP column to the "IS-IS Sub-TLVs for IS-IS Router
   CAPABILITY TLV" registry and populated it as shown in Table 6.

           +=========+====================================+====+
           | Value   | Name                               | MP |
           +=========+====================================+====+
           | 0       | Reserved                           |    |
           +---------+------------------------------------+----+
           | 1       | TE Node Capability Descriptor      | N  |
           +---------+------------------------------------+----+
           | 2       | Segment Routing Capability         | N  |
           +---------+------------------------------------+----+
           | 3       | TE-MESH-GROUP TLV (IPv4)           | Y  |
           +---------+------------------------------------+----+
           | 4       | TE-MESH-GROUP TLV (IPv6)           | Y  |
           +---------+------------------------------------+----+
           | 5       | PCED sub-TLV                       | N  |
           +---------+------------------------------------+----+
           | 6       | NICKNAME                           | Y  |
           +---------+------------------------------------+----+
           | 7       | TREES                              | N  |
           +---------+------------------------------------+----+
           | 8       | TREE-RT-IDs                        | Y  |
           +---------+------------------------------------+----+
           | 9       | TREE-USE-IDs                       | Y  |
           +---------+------------------------------------+----+
           | 10      | INT-VLAN                           | Y  |
           +---------+------------------------------------+----+
           | 11      | IPv4 TE Router ID                  | N  |
           +---------+------------------------------------+----+
           | 12      | IPv6 TE Router ID                  | N  |
           +---------+------------------------------------+----+
           | 13      | TRILL-VER                          | N  |
           +---------+------------------------------------+----+
           | 14      | VLAN-GROUP                         | Y  |
           +---------+------------------------------------+----+
           | 15      | INT-LABEL                          | Y  |
           +---------+------------------------------------+----+
           | 16      | RBCHANNELS                         | Y  |
           +---------+------------------------------------+----+
           | 17      | AFFINITY                           | Y  |
           +---------+------------------------------------+----+
           | 18      | LABEL-GROUP                        | Y  |
           +---------+------------------------------------+----+
           | 19      | Segment Routing Algorithm          | N  |
           +---------+------------------------------------+----+
           | 20      | S-BFD Discriminators               | N  |
           +---------+------------------------------------+----+
           | 21      | Node-Admin-Tag                     | N  |
           +---------+------------------------------------+----+
           | 22      | Segment Routing Local Block (SRLB) | N  |
           +---------+------------------------------------+----+
           | 23      | Node MSD                           | Y  |
           +---------+------------------------------------+----+
           | 24      | Segment Routing Mapping Server     | N  |
           |         | Preference (SRMS Preference)       |    |
           +---------+------------------------------------+----+
           | 25      | SRv6 Capabilities                  | N  |
           +---------+------------------------------------+----+
           | 26      | Flexible Algorithm Definition      | N  |
           |         | (FAD)                              |    |
           +---------+------------------------------------+----+
           | 27      | IS-IS Area Leader Sub-TLV          | N  |
           +---------+------------------------------------+----+
           | 28      | IS-IS Dynamic Flooding Sub-TLV     | N  |
           +---------+------------------------------------+----+
           | 29      | IP Algorithm Sub-TLV               | N  |
           +---------+------------------------------------+----+
           | 30-160  | Unassigned                         |    |
           +---------+------------------------------------+----+
           | 161     | Flood Reflection Discovery         | Y  |
           +---------+------------------------------------+----+
           | 162-255 | Unassigned                         |    |
           +---------+------------------------------------+----+

                  Table 6: IS-IS Sub-TLVs for IS-IS Router
                               CAPABILITY TLV

9.2.7.  IS-IS Sub-Sub-TLVs for SRv6 Capabilities Sub-TLV

   IANA has added the MP column to the "IS-IS Sub-Sub-TLVs for SRv6
   Capabilities Sub-TLV" registry and populated it as shown in Table 7.

                        +=======+============+====+
                        | Value | Name       | MP |
                        +=======+============+====+
                        | 0     | Reserved   |    |
                        +-------+------------+----+
                        | 1-255 | Unassigned |    |
                        +-------+------------+----+

                          Table 7: IS-IS Sub-Sub-
                               TLVs for SRv6
                            Capabilities Sub-TLV

9.2.8.  MP-TLV IS-IS Sub-Sub-TLVs for BIER Info Sub-TLV

   IANA has added the MP column to the "IS-IS Sub-Sub-TLVs for BIER Info
   Sub-TLV" registry and populated it as shown in Table 8.

                 +=======+=========================+====+
                 | Value | Name                    | MP |
                 +=======+=========================+====+
                 | 0     | Unassigned              |    |
                 +-------+-------------------------+----+
                 | 1     | BIER MPLS Encapsulation | N  |
                 +-------+-------------------------+----+
                 | 2     | BIER PHP Request        | N  |
                 +-------+-------------------------+----+
                 | 3-255 | Unassigned              |    |
                 +-------+-------------------------+----+

                   Table 8: IS-IS Sub-Sub-TLVs for BIER
                               Info Sub-TLV

9.2.9.  MP-TLV for IS-IS Sub-TLVs for Segment Identifier/Label Binding
        TLVs

   IANA has added the MP column to the "IS-IS Sub-TLVs for Segment
   Identifier/Label Binding TLVs" registry and populated it as shown in
   Table 9.

                +=======+===========================+====+
                | Value | Name                      | MP |
                +=======+===========================+====+
                | 0     | Reserved                  |    |
                +-------+---------------------------+----+
                | 1     | SID/Label                 | N  |
                +-------+---------------------------+----+
                | 2     | Unassigned                |    |
                +-------+---------------------------+----+
                | 3     | Prefix Segment Identifier | N  |
                +-------+---------------------------+----+
                | 4-255 | Unassigned                |    |
                +-------+---------------------------+----+

                   Table 9: IS-IS Sub-TLVs for Segment
                      Identifier/Label Binding TLVs

9.2.10.  MP-TLV for IS-IS Sub-Sub-TLV Codepoints for Application-
         Specific Link Attributes

   IANA has added the MP column to the "IS-IS Sub-Sub-TLV Codepoints for
   Application-Specific Link Attributes" registry and populated it as
   shown in Table 10.

           +========+====================================+====+
           | Value  | Name                               | MP |
           +========+====================================+====+
           | 0-2    | Unassigned                         |    |
           +--------+------------------------------------+----+
           | 3      | Administrative group (color)       | N  |
           +--------+------------------------------------+----+
           | 4-8    | Unassigned                         |    |
           +--------+------------------------------------+----+
           | 9      | Maximum link bandwidth             | N  |
           +--------+------------------------------------+----+
           | 10     | Maximum reservable link bandwidth  | N  |
           +--------+------------------------------------+----+
           | 11     | Unreserved bandwidth               | N  |
           +--------+------------------------------------+----+
           | 12-13  | Unassigned                         |    |
           +--------+------------------------------------+----+
           | 14     | Extended Administrative Group      | N  |
           +--------+------------------------------------+----+
           | 15-16  | Unassigned                         |    |
           +--------+------------------------------------+----+
           | 17     | Generic Metric                     | Y  |
           +--------+------------------------------------+----+
           | 18     | TE Default metric                  | N  |
           +--------+------------------------------------+----+
           | 19-32  | Unassigned                         |    |
           +--------+------------------------------------+----+
           | 33     | Unidirectional Link Delay          | N  |
           +--------+------------------------------------+----+
           | 34     | Min/Max Unidirectional Link Delay  | N  |
           +--------+------------------------------------+----+
           | 35     | Unidirectional Delay Variation     | N  |
           +--------+------------------------------------+----+
           | 36     | Unidirectional Link Loss           | N  |
           +--------+------------------------------------+----+
           | 37     | Unidirectional Residual Bandwidth  | N  |
           +--------+------------------------------------+----+
           | 38     | Unidirectional Available Bandwidth | N  |
           +--------+------------------------------------+----+
           | 39     | Unidirectional Utilized Bandwidth  | N  |
           +--------+------------------------------------+----+
           | 40-255 | Unassigned                         |    |
           +--------+------------------------------------+----+

                Table 10: IS-IS Sub-Sub-TLV Codepoints for
                   Application-Specific Link Attributes

9.2.11.  MP-TLV for IS-IS Sub-TLVs for Application-Specific SRLG TLV

   IANA has added the MP column to the "IS-IS Sub-TLVs for Application-
   Specific SRLG TLV" registry and populated it as shown in Table 11.

              +========+===============================+====+
              | Value  | Name                          | MP |
              +========+===============================+====+
              | 0-3    | Unassigned                    |    |
              +--------+-------------------------------+----+
              | 4      | Link Local/Remote Identifiers | N  |
              +--------+-------------------------------+----+
              | 5      | Unassigned                    |    |
              +--------+-------------------------------+----+
              | 6      | IPv4 interface address        | N  |
              +--------+-------------------------------+----+
              | 7      | Unassigned                    |    |
              +--------+-------------------------------+----+
              | 8      | IPv4 neighbor address         | N  |
              +--------+-------------------------------+----+
              | 9-11   | Unassigned                    |    |
              +--------+-------------------------------+----+
              | 12     | IPv6 Interface Address        | N  |
              +--------+-------------------------------+----+
              | 13     | IPv6 Neighbor Address         | N  |
              +--------+-------------------------------+----+
              | 14-255 | Unassigned                    |    |
              +--------+-------------------------------+----+

                 Table 11: IS-IS Sub-TLVs for Application-
                             Specific SRLG TLV

9.2.12.  MP-TLV for IS-IS Sub-Sub-TLVs for SRv6 SID Sub-TLVs

   IANA has added the MP column to the "IS-IS Sub-Sub-TLVs for SRv6 SID
   Sub-TLVs" registry and populated it as shown in Table 12.

                    +=======+====================+====+
                    | Value | Name               | MP |
                    +=======+====================+====+
                    | 0     | Reserved           |    |
                    +-------+--------------------+----+
                    | 1     | SRv6 SID Structure | N  |
                    +-------+--------------------+----+
                    | 2-255 | Unassigned         |    |
                    +-------+--------------------+----+

                        Table 12: IS-IS Sub-Sub-TLVs
                           for SRv6 SID Sub-TLVs

9.2.13.  MP-TLV for IS-IS Sub-Sub-TLVs for Flexible Algorithm Definition
         Sub-TLV

   IANA has added the MP column to the "IS-IS Sub-Sub-TLVs for Flexible
   Algorithm Definition Sub-TLV" registry and populated it as shown in
   Table 13.

       +========+============================================+====+
       | Value  | Name                                       | MP |
       +========+============================================+====+
       | 0      | Reserved                                   |    |
       +--------+--------------------------------------------+----+
       | 1      | Flexible Algorithm Exclude Admin Group     | N  |
       +--------+--------------------------------------------+----+
       | 2      | Flexible Algorithm Include-Any Admin Group | N  |
       +--------+--------------------------------------------+----+
       | 3      | Flexible Algorithm Include-All Admin Group | N  |
       +--------+--------------------------------------------+----+
       | 4      | Flexible Algorithm Definition Flags        | N  |
       +--------+--------------------------------------------+----+
       | 5      | Flexible Algorithm Exclude SRLG            | N  |
       +--------+--------------------------------------------+----+
       | 6      | IS-IS Exclude Minimum Bandwidth            | N  |
       +--------+--------------------------------------------+----+
       | 7      | IS-IS Exclude Maximum Delay                | N  |
       +--------+--------------------------------------------+----+
       | 8      | IS-IS Reference Bandwidth                  | N  |
       +--------+--------------------------------------------+----+
       | 9      | IS-IS Bandwidth Metric                     | N  |
       +--------+--------------------------------------------+----+
       | 10-255 | Unassigned                                 |    |
       +--------+--------------------------------------------+----+

           Table 13: IS-IS Sub-Sub-TLVs for Flexible Algorithm
                            Definition Sub-TLV

9.2.14.  MP-TLV for IS-IS Sub-Sub-TLVs for Flood Reflection Discovery
         Sub-TLV

   IANA has added the MP column to the "IS-IS Sub-Sub-TLVs for Flood
   Reflection Discovery Sub-TLV" registry and populated it as shown in
   Table 14.

             +=========+================================+====+
             | Value   | Name                           | MP |
             +=========+================================+====+
             | 0-160   | Unassigned                     |    |
             +---------+--------------------------------+----+
             | 161     | Flood Reflection Discovery     | N  |
             |         | Tunnel Encapsulation Attribute |    |
             +---------+--------------------------------+----+
             | 162-255 | Unassigned                     |    |
             +---------+--------------------------------+----+

                   Table 14: IS-IS Sub-Sub-TLVs for Flood
                        Reflection Discovery Sub-TLV

10.  Security Considerations

   This document creates no new security issues for IS-IS.  Additional
   instances of existing TLVs expose no new information.

   Note that support for MP-TLV may result in an implementation being
   more robust in handling unexpected occurrences of MP-TLV.

   Security concerns for IS-IS are addressed in [ISO10589], [RFC5304],
   and [RFC5310].

11.  References

11.1.  Normative References

   [ISO10589] ISO/IEC, "Information technology - Telecommunications and
              information exchange between systems - Intermediate System
              to Intermediate System intra-domain routeing information
              exchange protocol for use in conjunction with the protocol
              for providing the connectionless-mode network service (ISO
              8473)", ISO/IEC 10589:2002, November 2002,
              <https://www.iso.org/standard/30932.html>.

   [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/info/rfc2119>.

   [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,
              <https://www.rfc-editor.org/info/rfc5120>.

   [RFC5304]  Li, T. and R. Atkinson, "IS-IS Cryptographic
              Authentication", RFC 5304, DOI 10.17487/RFC5304, October
              2008, <https://www.rfc-editor.org/info/rfc5304>.

   [RFC5305]  Li, T. and H. Smit, "IS-IS Extensions for Traffic
              Engineering", RFC 5305, DOI 10.17487/RFC5305, October
              2008, <https://www.rfc-editor.org/info/rfc5305>.

   [RFC5307]  Kompella, K., Ed. and Y. Rekhter, Ed., "IS-IS Extensions
              in Support of Generalized Multi-Protocol Label Switching
              (GMPLS)", RFC 5307, DOI 10.17487/RFC5307, October 2008,
              <https://www.rfc-editor.org/info/rfc5307>.

   [RFC5310]  Bhatia, M., Manral, V., Li, T., Atkinson, R., White, R.,
              and M. Fanto, "IS-IS Generic Cryptographic
              Authentication", RFC 5310, DOI 10.17487/RFC5310, February
              2009, <https://www.rfc-editor.org/info/rfc5310>.

   [RFC6119]  Harrison, J., Berger, J., and M. Bartlett, "IPv6 Traffic
              Engineering in IS-IS", RFC 6119, DOI 10.17487/RFC6119,
              February 2011, <https://www.rfc-editor.org/info/rfc6119>.

   [RFC6213]  Hopps, C. and L. Ginsberg, "IS-IS BFD-Enabled TLV",
              RFC 6213, DOI 10.17487/RFC6213, April 2011,
              <https://www.rfc-editor.org/info/rfc6213>.

   [RFC7356]  Ginsberg, L., Previdi, S., and Y. Yang, "IS-IS Flooding
              Scope Link State PDUs (LSPs)", RFC 7356,
              DOI 10.17487/RFC7356, September 2014,
              <https://www.rfc-editor.org/info/rfc7356>.

   [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/info/rfc7981>.

   [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/info/rfc8174>.

   [RFC8202]  Ginsberg, L., Previdi, S., and W. Henderickx, "IS-IS
              Multi-Instance", RFC 8202, DOI 10.17487/RFC8202, June
              2017, <https://www.rfc-editor.org/info/rfc8202>.

   [RFC8918]  Ginsberg, L., Wells, P., Li, T., Przygienda, T., and S.
              Hegde, "Invalid TLV Handling in IS-IS", RFC 8918,
              DOI 10.17487/RFC8918, September 2020,
              <https://www.rfc-editor.org/info/rfc8918>.

   [RFC9479]  Ginsberg, L., Psenak, P., Previdi, S., Henderickx, W., and
              J. Drake, "IS-IS Application-Specific Link Attributes",
              RFC 9479, DOI 10.17487/RFC9479, October 2023,
              <https://www.rfc-editor.org/info/rfc9479>.

11.2.  Informative References

   [PICS-YANG]
              Qu, Y., Ginsberg, L., Przygienda, A., Decraene, B., and Y.
              Zhu, "YANG Model for IS-IS Protocol Implementation
              Conformance Statement (PICS)", Work in Progress, Internet-
              Draft, draft-ietf-lsr-isis-pics-yang-02, 20 October 2025,
              <https://datatracker.ietf.org/doc/html/draft-ietf-lsr-
              isis-pics-yang-02>.

Contributors

   The following individual made a substantial contribution to the
   content of this document and should be considered a coauthor:

   Chris Bowers
   Email: cbowers107@gmail.com


Authors' Addresses

   Parag Kaneriya
   Juniper Networks
   Elnath-Exora Business Park Survey
   Bangalore 560103
   Karnataka
   India
   Email: pkaneria@juniper.net


   Tony Li
   Juniper Networks
   1133 Innovation Way
   Sunnyvale, California 94089
   United States of America
   Email: tony.li@tony.li


   Antoni Przygienda
   Juniper Networks
   1133 Innovation Way
   Sunnyvale, California 94089
   United States of America
   Email: prz@juniper.net


   Shraddha Hegde
   Juniper Networks
   Elnath-Exora Business Park Survey
   Bangalore 560103
   Karnataka
   India
   Email: shraddha@juniper.net


   Les Ginsberg
   Cisco Systems
   Email: ginsberg@cisco.com
