LSR Working Group
Internet Engineering Task Force (IETF) P. Kaneriya
Internet-Draft
Request for Comments: 9885 T. Li
Intended status:
Category: Standards Track A. Przygienda
Expires: 25 December 2025
ISSN: 2070-1721 S. Hegde
Juniper Networks
L. Ginsberg
Cisco Systems
23 June
October 2025
Multi-Part TLVs in IS-IS
draft-ietf-lsr-multi-tlv-19
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
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This Internet-Draft will expire on 25 December 2025.
https://www.rfc-editor.org/info/rfc9885.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Requirements Language . . . . . . . . . . . . . . . . . . . . 4
3. Overview of MP-TLV Applicability to TLVs . . . . . . . . . . 4
3.1. TLVs That that Advertise a List of Objects . . . . . . . . . . 4
3.2. TLVs That that Advertise Objects with Identifier(s) . . . . . 5
3.2.1. Example: Extended IS Reachability . . . . . . . . . . 5
3.2.2. Example: Extended IP Reachability . . . . . . . . . . 5
4. Multi-Part TLVs . . . . . . . . . . . . . . . . . . . . . . . 6
5. Procedure for Receiving Multi-Part TLVs . . . . . . . . . . . 6
6. Specification of Applicability of Multi-Part TLV . . . . . . 8 TLVs
7. MP-TLV Capability Advertisement . . . . . . . . . . . . . . . 8
8. Deployment Considerations . . . . . . . . . . . . . . . . . . 10
8.1. Controls and Alarms . . . . . . . . . . . . . . . . . . . 10
8.2. Restrictions on Generation of MP-TLVs . . . . . . . . . . 10
9. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 11
9.1. MP-TLV Support sub-TLV . . . . . . . . . . . . . . . . . 11 Sub-TLV
9.2. Extension to IS-IS Top Level Top-Level TLV Registries . . . . . . . 11
9.2.1. MP-TLV for IS-IS Top-Level TLV Codepoints . . . . . . 11
9.2.2. MP-TLV for IS-IS Sub-TLVs for Reverse Metric TLV . . 15
9.2.3. MP-TLV for IS-IS Sub-TLVs for TLVs Advertising Neighbor
Information . . . . . . . . . . . . . . . . . . . . . 16
9.2.4. MP-TLV for IS-IS Sub-TLVs for TLVs Advertising Prefix
Reachability . . . . . . . . . . . . . . . . . . . . 18
9.2.5. MP-TLV for IS-IS Sub-TLVs for MT-Capability TLV . . . 19
9.2.6. MP-TLV for IS-IS Sub-TLVs for IS-IS Router CAPABILITY
TLV . . . . . . . . . . . . . . . . . . . . . . . . . 21
9.2.7. IS-IS Sub-Sub-TLVs for SRv6 Capabilities Sub-TLV . . 22
9.2.8. MP-TLV IS-IS Sub-Sub-TLVs for BIER Info Sub-TLV . . . 23
9.2.9. MP-TLV for IS-IS Sub-TLVs for Segment Identifier/Label
Binding TLVs . . . . . . . . . . . . . . . . . . . . 23
9.2.10. MP-TLV for IS-IS Sub-Sub-TLV Codepoints for
Application-Specific Link Attributes . . . . . . . . 23
9.2.11. MP-TLV for IS-IS Sub-TLVs for Application-Specific SRLG
TLV . . . . . . . . . . . . . . . . . . . . . . . . . 25
9.2.12. MP-TLV for IS-IS Sub-Sub-TLVs for SRv6 SID Sub-TLVs . . . . . . . . . . . . . . . . . . . . . . 25
9.2.13. MP-TLV for IS-IS Sub-Sub-TLVs for Flexible Algorithm
Definition Sub-TLV . . . . . . . . . . . . . . . . . 26
9.2.14. MP-TLV for IS-IS Sub-Sub-TLVs for Flood Reflection
Discovery Sub-TLV . . . . . . . . . . . . . . . . . . 27
10. Security Considerations . . . . . . . . . . . . . . . . . . . 27
11. Contributors . . . . . . . . . . . . . . . . . . . . . . . . 27
12. References . . . . . . . . . . . . . . . . . . . . . . . . . 27
12.1.
11.1. Normative References . . . . . . . . . . . . . . . . . . 27
12.2.
11.2. Informative References . . . . . . . . . . . . . . . . . 29
Contributors
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 29
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 Intermediate Systems 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), in which case the problem
addressed by this document would not exist. 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 8-bit length TLVs.
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, and defines 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
sub-sections.
subsections.
3.1. TLVs That 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 (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 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
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 (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 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 (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 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] [RFC8918].
5. Procedure for Receiving Multi-Part TLVs
A router that receives a 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 when on sending MP-TLVs.
The contents of a 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 a 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 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.
Specifying
The document defining the TLV should specify how to handle such cases is the responsibility of the
document that defines the TLV.
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 TLV 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
to
for all codepoints to which such procedures could be applied
contributes to potential interoperability problems if/when the there is
need
arises 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 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 mutiple 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
Type: 30 (suggested - to be assigned by IANA) 1 octet
Length (1 octet)
Length: 0 1 octet (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).
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 [I-D.ietf-lsr-isis-pics-yang]. [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 to 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 per-TLV basis, these controls SHOULD provide support per codepoint 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
This document requests Sub-TLV
IANA has registered the following code point from the "IS-IS Sub-
TLVs Sub-TLVs
for IS-IS Router CAPABILITY TLV" registry:
Type: 30 (suggested)
Description: MP-TLV Support for TLVs with implicit support
MP-TLV Applicability: N
Reference: This document Section 7.2 7 of RFC 9885
9.2. Extension to IS-IS Top Level Top-Level TLV Registries
This document requests
IANA to extend has extended a number of registries under the "IS-IS TLV
Codepoints" registries
(https://www.iana.org/assignments/isis-tlv-codepoints/isis-tlv-
codepoints.xhtml) registry group (<https://www.iana.org/assignments/isis-
tlv-codepoints/>) 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 sub-sections 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 sub-sections 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.
9.2.1. MP-TLV for IS-IS Top-Level TLV Codepoints
(https://www.iana.org/assignments/isis-tlv-codepoints/isis-tlv-
codepoints.xhtml#tlv-codepoints)
+===========+========================================+====+
+===========+====================================+====+
| 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 TLV | N |
+-----------+----------------------------------------+----+
+-----------+------------------------------------+----+
| 127 | IPv6 Algorithm Prefix Reachability TLV | 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
(https://www.iana.org/assignments/isis-tlv-codepoints/isis-tlv-
codepoints.xhtml#tlv-16)
+========+============================+====+
| 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
(https://www.iana.org/assignments/isis-tlv-codepoints/isis-tlv-
codepoints.xhtml#isis-tlv-codepoints-advertising-neighbor-
information)
+=========+===================================================+====+
| 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
(https://www.iana.org/assignments/isis-tlv-codepoints/isis-tlv-
codepoints.xhtml#isis-tlv-codepoints-advertising-prefix-reachability)
+========+=========================================+====+
| 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 |
+--------+-----------------------------------------+----+
| 32-255 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
(https://www.iana.org/assignments/isis-tlv-codepoints/isis-tlv-
codepoints.xhtml#tlv-144)
+========+==============================+====+
| 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
(https://www.iana.org/assignments/isis-tlv-codepoints/isis-tlv-
codepoints.xhtml#isis-tlv-codepoints-242)
+=========+====================================+====+
| 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
(https://www.iana.org/assignments/isis-tlv-codepoints/isis-tlv-
codepoints.xhtml#isis-sub-sub-tlv-srv6-capability)
+=======+============+====+
| 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
(https://www.iana.org/assignments/isis-tlv-codepoints/isis-tlv-
codepoints.xhtml#bier-info-sub-tlv)
+=======+=========================+====+
| 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
(https://www.iana.org/assignments/isis-tlv-codepoints/isis-tlv-
codepoints.xhtml#tlv-149-150)
+=======+===========================+====+
| 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
(https://www.iana.org/assignments/isis-tlv-codepoints/isis-tlv-
codepoints.xhtml#application-specific-link-attributes)
+========+====================================+====+
| 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 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
(https://www.iana.org/assignments/isis-tlv-codepoints/isis-tlv-
codepoints.xhtml#tlv-238)
+========+===============================+====+
| 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
(https://www.iana.org/assignments/isis-tlv-codepoints/isis-tlv-
codepoints.xhtml#isis-sub-sub-tlvs-srv6-sid-sub-tlvs)
+=======+====================+====+
| 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
(https://www.iana.org/assignments/isis-tlv-codepoints/isis-tlv-
codepoints.xhtml#isis-sub-sub-tlvs-flexible-algorithm-definition-sub-
tlv)
+========+============================================+====+
| 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 Threshold 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
(https://www.iana.org/assignments/isis-tlv-codepoints/isis-tlv-
codepoints.xhtml#isis-sub-sub-tlvs-flood-reflection-discovery-sub-
tlv)
+=========+================================+====+
| 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. Contributors
The following people gave a substantial contribution to the content
of this document and should be considered coauthors:
Chris Bowers
Email: cbowers107@gmail.com
12. References
12.1.
11.1. Normative References
[ISO10589] ISO, "Intermediate system ISO/IEC, "Information technology - Telecommunications and
information exchange between systems - Intermediate System
to Intermediate system routing System intra-domain routeing information
exchange protocol for use in conjunction with the Protocol protocol
for providing the Connectionless-mode Network
Service connectionless-mode network service (ISO
8473)", ISO/IEC 10589:2002, November 2002, <ISO/IEC 10589:2002>.
<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>.
12.2.
11.2. Informative References
[I-D.ietf-lsr-isis-pics-yang]
[PICS-YANG]
Qu, Y., Ginsberg, L., Przygienda, T., 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-01, 5 May 2025,
<https://datatracker.ietf.org/doc/html/draft-ietf-lsr-
isis-pics-yang-01>.
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