rfc9479.original   rfc9479.txt 
Networking Working Group L. Ginsberg Internet Engineering Task Force (IETF) L. Ginsberg
Internet-Draft P. Psenak Request for Comments: 9479 P. Psenak
Obsoletes: 8919 (if approved) Cisco Systems Obsoletes: 8919 Cisco Systems
Intended status: Standards Track S. Previdi Category: Standards Track S. Previdi
Expires: 26 November 2023 Huawei Technologies ISSN: 2070-1721 Huawei Technologies
W. Henderickx W. Henderickx
Nokia Nokia
J. Drake J. Drake
Juniper Networks Juniper Networks
25 May 2023 October 2023
IS-IS Application-Specific Link Attributes IS-IS Application-Specific Link Attributes
draft-ietf-lsr-rfc8919bis-04
Abstract Abstract
Existing traffic-engineering-related link attribute advertisements Existing traffic-engineering-related link attribute advertisements
have been defined and are used in RSVP-TE deployments. Since the have been defined and are used in RSVP-TE deployments. Since the
original RSVP-TE use case was defined, additional applications (e.g., original RSVP-TE use case was defined, additional applications (e.g.,
Segment Routing Policy and Loop-Free Alternates) that also make use Segment Routing Policy and Loop-Free Alternates) that also make use
of the link attribute advertisements have been defined. In cases of the link attribute advertisements have been defined. In cases
where multiple applications wish to make use of these link where multiple applications wish to make use of these link
attributes, the current advertisements do not support application- attributes, the current advertisements do not support application-
specific values for a given attribute, nor do they support indication specific values for a given attribute, nor do they support an
of which applications are using the advertised value for a given indication of which applications are using the advertised value for a
link. This document introduces new link attribute advertisements given link. This document introduces link attribute advertisements
that address both of these shortcomings. that address both of these shortcomings.
This document obsoletes RFC 8919. This document obsoletes RFC 8919.
Status of This Memo Status of This Memo
This Internet-Draft is submitted in full conformance with the This is an Internet Standards Track document.
provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet-
Drafts is at https://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months This document is a product of the Internet Engineering Task Force
and may be updated, replaced, or obsoleted by other documents at any (IETF). It represents the consensus of the IETF community. It has
time. It is inappropriate to use Internet-Drafts as reference received public review and has been approved for publication by the
material or to cite them other than as "work in progress." Internet Engineering Steering Group (IESG). Further information on
Internet Standards is available in Section 2 of RFC 7841.
This Internet-Draft will expire on 26 November 2023. 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/rfc9479.
Copyright Notice Copyright Notice
Copyright (c) 2023 IETF Trust and the persons identified as the Copyright (c) 2023 IETF Trust and the persons identified as the
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Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3 1. Introduction
1.1. Requirements Language . . . . . . . . . . . . . . . . . . 4 1.1. Requirements Language
2. Requirements Discussion . . . . . . . . . . . . . . . . . . . 4 2. Requirements Discussion
3. Legacy Advertisements . . . . . . . . . . . . . . . . . . . . 5 3. Legacy Advertisements
3.1. Legacy Sub-TLVs . . . . . . . . . . . . . . . . . . . . . 5 3.1. Legacy Sub-TLVs
3.2. Legacy SRLG Advertisements . . . . . . . . . . . . . . . 6 3.2. Legacy SRLG Advertisements
4. Advertising Application-Specific Link Attributes . . . . . . 6 4. Advertising Application-Specific Link Attributes
4.1. Application Identifier Bit Mask . . . . . . . . . . . . . 7 4.1. Application Identifier Bit Mask
4.2. Application-Specific Link Attributes Sub-TLV . . . . . . 9 4.2. Application-Specific Link Attributes Sub-TLV
4.2.1. Special Considerations for Maximum Link Bandwidth . . 10 4.2.1. Special Considerations for Maximum Link Bandwidth
4.2.2. Special Considerations for Reservable/Unreserved 4.2.2. Special Considerations for Reservable/Unreserved
Bandwidth . . . . . . . . . . . . . . . . . . . . . . 11 Bandwidth
4.2.3. Considerations for Extended TE Metrics . . . . . . . 11 4.2.3. Considerations for Extended TE Metrics
4.3. Application-Specific SRLG TLV . . . . . . . . . . . . . . 11 4.3. Application-Specific SRLG TLV
5. Attribute Advertisements and Enablement . . . . . . . . . . . 13 5. Attribute Advertisements and Enablement
6. Deployment Considerations . . . . . . . . . . . . . . . . . . 14 6. Deployment Considerations
6.1. Use of Legacy Advertisements . . . . . . . . . . . . . . 14 6.1. Use of Legacy Advertisements
6.2. Use of Zero-Length Application Identifier Bit Masks . . . 15 6.2. Use of Zero-Length Application Identifier Bit Masks
6.3. Interoperability, Backwards Compatibility, and Migration 6.3. Interoperability, Backwards Compatibility, and Migration
Concerns . . . . . . . . . . . . . . . . . . . . . . . . 15 Concerns
6.3.1. Multiple Applications: Common Attributes with 6.3.1. Multiple Applications: Common Attributes with RSVP-TE
RSVP-TE . . . . . . . . . . . . . . . . . . . . . . . 15
6.3.2. Multiple Applications: All Attributes Not Shared with 6.3.2. Multiple Applications: All Attributes Not Shared with
RSVP-TE . . . . . . . . . . . . . . . . . . . . . . . 16 RSVP-TE
6.3.3. Interoperability with Legacy Routers . . . . . . . . 16 6.3.3. Interoperability with Legacy Routers
6.3.4. Use of Application-Specific Advertisements for 6.3.4. Use of Application-Specific Advertisements for RSVP-TE
RSVP-TE . . . . . . . . . . . . . . . . . . . . . . . 17 7. IANA Considerations
7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 17 7.1. Application-Specific Link Attributes Sub-TLV
7.1. Application-Specific Link Attributes Sub-TLV . . . . . . 17 7.2. Application-Specific SRLG TLV
7.2. Application-Specific SRLG TLV . . . . . . . . . . . . . . 18 7.3. IS-IS Sub-Sub-TLV Codepoints for Application-Specific Link
7.3. Sub-sub-TLV Codepoints for Application-Specific Link Attributes Registry
Attributes Registry . . . . . . . . . . . . . . . . . . . 18 7.4. Link Attribute Application Identifiers Registry
7.5. IS-IS Sub-TLVs for Application-Specific SRLG TLV
7.4. Link Attribute Application Identifiers Registry . . . . . 20 8. Security Considerations
7.5. Sub-TLVs for TLV 238 Registry . . . . . . . . . . . . . . 20 9. Changes to RFC 8919
8. Security Considerations . . . . . . . . . . . . . . . . . . . 21 10. References
9. Changes to RFC 8919 . . . . . . . . . . . . . . . . . . . . . 22 10.1. Normative References
10. References . . . . . . . . . . . . . . . . . . . . . . . . . 22 10.2. Informative References
10.1. Normative References . . . . . . . . . . . . . . . . . . 22 Acknowledgements
10.2. Informative References . . . . . . . . . . . . . . . . . 23 Authors' Addresses
Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . . 24
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 24
1. Introduction 1. Introduction
NOTE: This document makes modest editorial changes to the content of
RFC 8919 which it obsoletes. A detailed description of the changes
is provided in Section 9. This note was added for the benefit of
IESG reviewers and SHOULD be removed by the RFC Editor prior to
publication.
Advertisement of link attributes by the Intermediate System to Advertisement of link attributes by the Intermediate System to
Intermediate System (IS-IS) protocol in support of traffic Intermediate System (IS-IS) protocol in support of Traffic
engineering (TE) was introduced by [RFC5305] and extended by Engineering (TE) was introduced by [RFC5305] and extended by
[RFC5307], [RFC6119], [RFC7308], and [RFC8570]. Use of these [RFC5307], [RFC6119], [RFC7308], and [RFC8570]. The use of these
extensions has been associated with deployments supporting Traffic extensions has been associated with deployments supporting TE over
Engineering over Multiprotocol Label Switching (MPLS) in the presence Multiprotocol Label Switching (MPLS) in the presence of the Resource
of the Resource Reservation Protocol (RSVP), more succinctly referred Reservation Protocol (RSVP), more succinctly referred to as RSVP-TE
to as RSVP-TE [RFC3209]. [RFC3209].
For the purposes of this document, an application is a technology For the purposes of this document, an application is a technology
that makes use of link attribute advertisements, examples of which that makes use of link attribute advertisements, examples of which
are listed in Section 3. are listed in Section 3.
In recent years, new applications that have use cases for many of the In recent years, new applications that have use cases for many of the
link attributes historically used by RSVP-TE have been introduced. link attributes historically used by RSVP-TE have been introduced.
Such applications include Segment Routing (SR) Policy Such applications include Segment Routing (SR) Policy [RFC9256] and
[SEGMENT-ROUTING] and Loop-Free Alternates (LFAs) [RFC5286]. This Loop-Free Alternates (LFAs) [RFC5286]. This has introduced ambiguity
has introduced ambiguity in that if a deployment includes a mix of in that if a deployment includes a mix of RSVP-TE support and SR
RSVP-TE support and SR Policy support, for example, it is not Policy support, for example, it is not possible to unambiguously
possible to unambiguously indicate which advertisements are to be indicate which advertisements are to be used by RSVP-TE and which
used by RSVP-TE and which advertisements are to be used by SR Policy. advertisements are to be used by SR Policy. If the topologies are
If the topologies are fully congruent, this may not be an issue, but fully congruent, this may not be an issue, but any incongruence leads
any incongruence leads to ambiguity. to ambiguity.
An example of where this ambiguity causes a problem is a network An example of where this ambiguity causes a problem is a network
where RSVP-TE is enabled only on a subset of its links. A link where RSVP-TE is enabled only on a subset of its links. A link
attribute is advertised for the purpose of another application (e.g., attribute is advertised for the purpose of another application (e.g.,
SR Policy) for a link that is not enabled for RSVP-TE. As soon as SR Policy) for a link that is not enabled for RSVP-TE. As soon as
the router that is an RSVP-TE head end sees the link attribute being the router that is an RSVP-TE head end sees the link attribute being
advertised for that link, it assumes RSVP-TE is enabled on that link, advertised for that link, it assumes that RSVP-TE is enabled on that
even though it is not. If such an RSVP-TE head-end router tries to link, even though it is not. If such an RSVP-TE head-end router
set up an RSVP-TE path via that link, it will result in a path setup tries to set up an RSVP-TE path via that link, it will result in a
failure. setup failure for the path.
An additional issue arises in cases where both applications are An additional issue arises in cases where both applications are
supported on a link but the link attribute values associated with supported on a link but the link attribute values associated with
each application differ. Current advertisements do not support each application differ. Current advertisements do not support
advertising application-specific values for the same attribute on a advertising application-specific values for the same attribute on a
specific link. specific link.
This document defines extensions that address these issues. Also, as This document defines extensions that address these issues. Also, as
evolution of use cases for link attributes can be expected to evolution of use cases for link attributes can be expected to
continue in the years to come, this document defines a solution that continue in the years to come, this document defines a solution that
skipping to change at page 4, line 35 skipping to change at line 165
BCP 14 [RFC2119] [RFC8174] when, and only when, they appear in all BCP 14 [RFC2119] [RFC8174] when, and only when, they appear in all
capitals, as shown here. capitals, as shown here.
2. Requirements Discussion 2. Requirements Discussion
As stated previously, evolution of use cases for link attributes can As stated previously, evolution of use cases for link attributes can
be expected to continue. Therefore, any discussion of existing use be expected to continue. Therefore, any discussion of existing use
cases is limited to requirements that are known at the time of this cases is limited to requirements that are known at the time of this
writing. However, in order to determine the functionality required writing. However, in order to determine the functionality required
beyond what already exists in IS-IS, it is only necessary to discuss beyond what already exists in IS-IS, it is only necessary to discuss
use cases that justify the key points identified in the introduction, use cases that justify the key points identified in the Introduction,
which are: which are:
1. Support for indicating which applications are using the link 1. Support for indicating which applications are using the link
attribute advertisements on a link attribute advertisements on a link.
2. Support for advertising application-specific values for the same 2. Support for advertising application-specific values for the same
attribute on a link attribute on a link.
[RFC7855] discusses use cases and requirements for Segment Routing [RFC7855] discusses use cases and requirements for SR. Included
(SR). Included among these use cases is SR Policy, which is defined among these use cases is SR Policy, which is defined in [RFC9256].
in [SEGMENT-ROUTING]. If both RSVP-TE and SR Policy are deployed in If both RSVP-TE and SR Policy are deployed in a network, link
a network, link attribute advertisements can be used by one or both attribute advertisements can be used by one or both of these
of these applications. There is no requirement for the link applications. There is no requirement for the link attributes
attributes advertised on a given link used by SR Policy to be advertised on a given link used by SR Policy to be identical to the
identical to the link attributes advertised on that same link used by link attributes advertised on that same link used by RSVP-TE; thus,
RSVP-TE; thus, there is a clear requirement to indicate independently there is a clear requirement to indicate independently which link
which link attribute advertisements are to be used by each attribute advertisements are to be used by each application.
application.
As the number of applications that may wish to utilize link As the number of applications that may wish to utilize link
attributes may grow in the future, an additional requirement is that attributes may grow in the future, an additional requirement is that
the extensions defined allow the association of additional the extensions defined allow the association of additional
applications to link attributes without altering the format of the applications to link attributes without altering the format of the
advertisements or introducing new backwards-compatibility issues. advertisements or introducing backwards-compatibility issues.
Finally, there may still be many cases where a single attribute value Finally, there may still be many cases where a single attribute value
can be shared among multiple applications, so the solution must can be shared among multiple applications, so the solution must
minimize advertising duplicate link/attribute pairs whenever minimize advertising duplicate link/attribute pairs whenever
possible. possible.
3. Legacy Advertisements 3. Legacy Advertisements
Existing advertisements used in support of RSVP-TE include sub-TLVs Existing advertisements used in support of RSVP-TE include sub-TLVs
for TLVs Advertising Neighbor Information and TLVs for Shared Risk for TLVs Advertising Neighbor Information and TLVs for Shared Risk
Link Group (SRLG) advertisement. Link Group (SRLG) advertisements.
Sub-TLV values are defined in the "IS-IS sub-TLVs for TLVs Sub-TLV values are defined in the "IS-IS Sub-TLVs for TLVs
Advertising Neighbor Information" registry. Advertising Neighbor Information" registry.
TLVs are defined in the "TLV Codepoints Registry". TLVs are defined in the "IS-IS TLV Codepoints" registry.
3.1. Legacy Sub-TLVs 3.1. Legacy Sub-TLVs
+======+====================================+ +======+====================================+
| Type | Description | | Type | Description |
+======+====================================+ +======+====================================+
| 3 | Administrative group (color) | | 3 | Administrative group (color) |
+------+------------------------------------+ +------+------------------------------------+
| 9 | Maximum link bandwidth | | 9 | Maximum link bandwidth |
+------+------------------------------------+ +------+------------------------------------+
| 10 | Maximum reservable link bandwidth | | 10 | Maximum reservable link bandwidth |
+------+------------------------------------+ +------+------------------------------------+
| 11 | Unreserved bandwidth | | 11 | Unreserved bandwidth |
+------+------------------------------------+ +------+------------------------------------+
| 14 | Extended Administrative Group | | 14 | Extended Administrative Group |
+------+------------------------------------+ +------+------------------------------------+
| 18 | TE Default Metric | | 18 | TE Default metric |
+------+------------------------------------+ +------+------------------------------------+
| 33 | Unidirectional Link Delay | | 33 | Unidirectional Link Delay |
+------+------------------------------------+ +------+------------------------------------+
| 34 | Min/Max Unidirectional Link Delay | | 34 | Min/Max Unidirectional Link Delay |
+------+------------------------------------+ +------+------------------------------------+
| 35 | Unidirectional Delay Variation | | 35 | Unidirectional Delay Variation |
+------+------------------------------------+ +------+------------------------------------+
| 36 | Unidirectional Link Loss | | 36 | Unidirectional Link Loss |
+------+------------------------------------+ +------+------------------------------------+
| 37 | Unidirectional Residual Bandwidth | | 37 | Unidirectional Residual Bandwidth |
+------+------------------------------------+ +------+------------------------------------+
| 38 | Unidirectional Available Bandwidth | | 38 | Unidirectional Available Bandwidth |
+------+------------------------------------+ +------+------------------------------------+
| 39 | Unidirectional Utilized Bandwidth | | 39 | Unidirectional Utilized Bandwidth |
+------+------------------------------------+ +------+------------------------------------+
Table 1: Sub-TLVs for TLVs Advertising Table 1
Neighbor Information
3.2. Legacy SRLG Advertisements 3.2. Legacy SRLG Advertisements
TLV 138 (GMPLS-SRLG): TLV 138 (GMPLS-SRLG):
Supports links identified by IPv4 addresses and unnumbered links. Supports links identified by IPv4 addresses and unnumbered links.
TLV 139 (IPv6 SRLG): TLV 139 (IPv6 SRLG):
Supports links identified by IPv6 addresses. Supports links identified by IPv6 addresses.
Note that [RFC6119] prohibits the use of TLV 139 when it is possible Note that [RFC6119] prohibits the use of TLV 139 when it is possible
to use TLV 138. to use TLV 138.
4. Advertising Application-Specific Link Attributes 4. Advertising Application-Specific Link Attributes
Two new codepoints are defined to support Application-Specific Link Two codepoints are defined to support Application-Specific Link
Attribute (ASLA) advertisements: Attribute (ASLA) advertisements:
1) Application-Specific Link Attributes sub-TLV for TLVs Advertising 1. Application-Specific Link Attributes sub-TLV for TLVs Advertising
Neighbor Information (defined in Section 4.2). Neighbor Information (defined in Section 4.2).
2) Application-Specific Shared Risk Link Group (SRLG) TLV (defined 2. Application-Specific SRLG TLV (defined in Section 4.3).
in Section 4.3).
To support these new advertisements, an application identifier bit To support these advertisements, an application identifier bit mask
mask is defined to identify the application(s) associated with a is defined to identify the application(s) associated with a given
given advertisement (defined in Section 4.1). advertisement (defined in Section 4.1).
In addition to supporting the advertisement of link attributes used In addition to supporting the advertisement of link attributes used
by standardized applications, link attributes can also be advertised by standardized applications, link attributes can also be advertised
for use by user-defined applications. Such applications are not for use by User-Defined Applications (UDAs). Such applications are
subject to standardization and are outside the scope of this not subject to standardization and are outside the scope of this
document. document.
The following sections define the format of these new advertisements. The following sections define the format of these advertisements.
4.1. Application Identifier Bit Mask 4.1. Application Identifier Bit Mask
Identification of the set of applications associated with link Identification of the set of applications associated with link
attribute advertisements utilizes two bit masks. One bit mask is for attribute advertisements utilizes two bit masks. One bit mask is for
standard applications where the definition of each bit is defined in standard applications where the definition of each bit is defined in
a new IANA-controlled registry (see Section 7.4). A second bit mask an IANA-controlled registry (see Section 7.4). A second bit mask is
is for non-standard user-defined applications (UDAs). for non-standard UDAs.
The encoding defined below is used by both the Application-Specific The encoding defined below is used by both the Application-Specific
Link Attributes sub-TLV and the Application-Specific SRLG TLV. Link Attributes sub-TLV and the Application-Specific SRLG TLV.
0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7
+--+--+--+--+--+--+--+--+ +--+--+--+--+--+--+--+--+
| SABM Length + Flag | 1 octet | SABM Length + Flag | 1 octet
+--+--+--+--+--+--+--+--+ +--+--+--+--+--+--+--+--+
| UDABM Length + Flag | 1 octet | UDABM Length + Flag | 1 octet
+--+--+--+--+--+--+--+--+ +--+--+--+--+--+--+--+--+
| SABM ... 0 - 8 octets | SABM ... 0-8 octets
+--+--+--+--+--+--+--+--+ +--+--+--+--+--+--+--+--+
| UDABM ... 0 - 8 octets | UDABM ... 0-8 octets
+--+--+--+--+--+--+--+--+ +--+--+--+--+--+--+--+--+
SABM Length + Flag (1 octet): Standard Application Identifier Bit SABM Length + Flag (1 octet):
Mask Length + Flag Standard Application Identifier Bit Mask Length + Flag
0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7
+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+
|L| SABM Length | |L| SABM Length |
+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+
L-flag: Legacy Flag. See Section 4.2 for a description of how L-flag:
this flag is used. Legacy Flag. See Section 4.2 for a description of how this
flag is used.
SABM Length: Indicates the length in octets (0-8) of the Standard SABM Length:
This field indicates the length in octets (0-8) of the Standard
Application Identifier Bit Mask. The length SHOULD be the Application Identifier Bit Mask. The length SHOULD be the
minimum required to send all bits that are set. minimum required to send all bits that are set.
UDABM Length + Flag (1 octet): User-Defined Application Identifier UDABM Length + Flag (1 octet):
Bit Mask Length + Flag User-Defined Application Identifier Bit Mask Length + Flag
0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7
+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+
|R| UDABM Length| |R| UDABM Length|
+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+
R: Reserved. SHOULD be transmitted as 0 and MUST be ignored on R:
Reserved. SHOULD be transmitted as 0 and MUST be ignored on
receipt. receipt.
UDABM Length: Indicates the length in octets (0-8) of the User- UDABM Length:
Defined Application Identifier Bit Mask. The length SHOULD be Indicates the length in octets (0-8) of the User-Defined
the minimum required to send all bits that are set. Application Identifier Bit Mask. The length SHOULD be the
minimum required to send all bits that are set.
SABM (variable length): Standard Application Identifier Bit Mask SABM (variable length):
Standard Application Identifier Bit Mask
(SABM Length * 8) bits (SABM Length * 8) bits
This field is omitted if SABM Length is 0. This field is omitted if SABM Length is 0.
0 1 2 3 4 5 6 7 ... 0 1 2 3 4 5 6 7 ...
+-+-+-+-+-+-+-+-+... +-+-+-+-+-+-+-+-+...
|R|S|F| ... |R|S|F| ...
+-+-+-+-+-+-+-+-+... +-+-+-+-+-+-+-+-+...
R-bit: Set to specify RSVP-TE. R-bit:
Set to specify RSVP-TE.
S-bit: Set to specify Segment Routing Policy (this is dataplane S-bit:
independent). Set to specify SR Policy (this is data plane independent).
F-bit: Set to specify Loop-Free Alternate (LFA) (includes all LFA F-bit:
types). Set to specify an LFA (includes all LFA types).
UDABM (variable length): User-Defined Application Identifier Bit UDABM (variable length):
Mask User-Defined Application Identifier Bit Mask
(UDABM Length * 8) bits (UDABM Length * 8) bits
0 1 2 3 4 5 6 7 ... 0 1 2 3 4 5 6 7 ...
+-+-+-+-+-+-+-+-+... +-+-+-+-+-+-+-+-+...
| ... | ...
+-+-+-+-+-+-+-+-+... +-+-+-+-+-+-+-+-+...
This field is omitted if UDABM Length is 0. This field is omitted if UDABM Length is 0.
skipping to change at page 9, line 14 skipping to change at line 375
Standard Application Identifier Bits are defined and sent starting Standard Application Identifier Bits are defined and sent starting
with bit 0. with bit 0.
User-Defined Application Identifier Bits have no relationship to User-Defined Application Identifier Bits have no relationship to
Standard Application Identifier Bits and are not managed by IANA or Standard Application Identifier Bits and are not managed by IANA or
any other standards body. It is recommended that bits be used any other standards body. It is recommended that bits be used
starting with bit 0 so as to minimize the number of octets required starting with bit 0 so as to minimize the number of octets required
to advertise all UDAs. to advertise all UDAs.
For both SABM and UDABM, the following rules apply: For both the SABM and UDABM, the following rules apply:
* Undefined bits that are transmitted MUST be transmitted as 0 and * Undefined bits that are transmitted MUST be transmitted as 0 and
MUST be ignored on receipt. MUST be ignored on receipt.
* Bits that are not transmitted MUST be treated as if they are set * Bits that are not transmitted MUST be treated as if they are set
to 0 on receipt. to 0 on receipt.
* Bits that are not supported by an implementation MUST be ignored * Bits that are not supported by an implementation MUST be ignored
on receipt. on receipt.
4.2. Application-Specific Link Attributes Sub-TLV 4.2. Application-Specific Link Attributes Sub-TLV
A new sub-TLV for TLVs Advertising Neighbor Information is defined A sub-TLV for TLVs Advertising Neighbor Information is defined that
that supports specification of the applications and application- supports specification of the applications and application-specific
specific attribute values. attribute values.
Type: 16 Type:
16
Length: Variable (1 octet) Length:
Variable (1 octet)
Value: Value:
Application Identifier Bit Mask (as defined in Section 4.1) Application Identifier Bit Mask (as defined in Section 4.1)
Link Attribute sub-sub-TLVs -- format matches the existing Link Attribute sub-sub-TLVs -- format matches the existing formats
formats defined in [RFC5305], [RFC7308], and [RFC8570] defined in [RFC5305], [RFC7308], and [RFC8570]
If the SABM or UDABM Length in the Application Identifier Bit Mask is If the SABM Length or UDABM Length in the Application Identifier Bit
greater than 8, the entire sub-TLV MUST be ignored. Mask is greater than 8, the entire sub-TLV MUST be ignored.
When SABM or UDABM Length is non-zero and the L-flag is NOT set, all When the SABM Length or UDABM Length is non-zero and the L-flag is
applications specified in the bit mask MUST use the link attribute NOT set, all applications specified in the bit mask MUST use the link
advertisements in the sub-TLV. attribute advertisements in the sub-TLV.
When the L-flag is set in the Application Identifier Bit Mask, all of When the L-flag is set in the Application Identifier Bit Mask, all of
the applications specified in the bit mask MUST use the legacy the applications specified in the bit mask MUST use the legacy
advertisements for the corresponding link found in TLVs Advertising advertisements for the corresponding link found in TLVs Advertising
Neighbor Information. Link attribute sub-sub-TLVs for the Neighbor Information. Link attribute sub-sub-TLVs for the
corresponding link attributes MUST NOT be advertised for the set of corresponding link attributes MUST NOT be advertised for the set of
applications specified in the Standard or User-Defined Application applications specified in the Standard Application Identifier Bit
Identifier Bit Masks, and all such sub-sub-TLVs MUST be ignored on Mask or the User-Defined Application Identifier Bit Mask, and all
receipt. such sub-sub-TLVs MUST be ignored on receipt.
Multiple Application-Specific Link Attributes sub-TLVs for the same Multiple Application-Specific Link Attributes sub-TLVs for the same
link MAY be advertised. When multiple sub-TLVs for the same link are link MAY be advertised. When multiple sub-TLVs for the same link are
advertised, they SHOULD advertise non-conflicting application/ advertised, they SHOULD advertise non-conflicting application/
attribute pairs. A conflict exists when the same application is attribute pairs. A conflict exists when the same application is
associated with two different values for the same link attribute for associated with two different values for the same link attribute for
a given link. In cases where conflicting values for the same a given link. In cases where conflicting values for the same
application/attribute/link are advertised, the first advertisement application/attribute/link are advertised, the first advertisement
received in the lowest-numbered LSP MUST be used, and subsequent received in the lowest-numbered Link State Protocol Data Unit (LSP)
advertisements of the same attribute MUST be ignored. MUST be used, and subsequent advertisements of the same attribute
MUST be ignored.
For a given application, the setting of the L-flag MUST be the same For a given application, the setting of the L-flag MUST be the same
in all sub-TLVs for a given link. In cases where this constraint is in all sub-TLVs for a given link. In cases where this constraint is
violated, the L-flag MUST be considered set for this application. violated, the L-flag MUST be considered set for this application.
The end result of the set of rules defined above is that for a given The end result of the set of rules defined above is that for a given
application either the attribute values advertised in ASLA sub-sub- application either the attribute values advertised in ASLA sub-sub-
TLVs are used or the attribute values advertised in Legacy sub-TLVs TLVs are used or the attribute values advertised in legacy sub-TLVs
are used, but not both. are used, but not both.
Link attributes MAY be advertised associated with zero-length Link attributes MAY be advertised associated with zero-length
Application Identifier Bit Masks for both standard applications and Application Identifier Bit Masks for both standard applications and
user-defined applications. Such link attribute advertisements MUST UDAs. Such link attribute advertisements MUST be used by standard
be used by standard applications and/or user defined applications applications and/or UDAs when no link attribute advertisements with a
when no link attribute advertisements with a non-zero-length non-zero-length Application Identifier Bit Mask and a matching
Application Identifier Bit Mask and a matching Application Identifier Application Identifier Bit set are present for a given link.
Bit set are present for a given link. Otherwise, such link attribute Otherwise, such link attribute advertisements MUST NOT be used.
advertisements MUST NOT be used.
IANA has created a new registry of sub-sub-TLVs to define the link IANA has created a registry of sub-sub-TLVs to define the link
attribute sub-sub-TLV codepoints (see Section 7.3). This document attribute sub-sub-TLV codepoints (see Section 7.3). This document
defines a sub-sub-TLV for each of the existing sub-TLVs listed in defines a sub-sub-TLV for each of the existing sub-TLVs listed in
Section 3.1, except as noted below. The format of the sub-sub-TLVs Section 3.1, except as noted below. The format of the sub-sub-TLVs
matches the format of the corresponding legacy sub-TLV, and IANA has matches the format of the corresponding legacy sub-TLV, and IANA has
assigned the legacy sub-TLV identifier to the corresponding sub-sub- assigned the legacy sub-TLV identifier to the corresponding sub-sub-
TLV. TLV.
4.2.1. Special Considerations for Maximum Link Bandwidth 4.2.1. Special Considerations for Maximum Link Bandwidth
Maximum link bandwidth is an application-independent attribute of the Maximum link bandwidth is an application-independent attribute of the
skipping to change at page 11, line 11 skipping to change at line 471
This can be accomplished most efficiently by having a single This can be accomplished most efficiently by having a single
advertisement for a given link where the Application Identifier Bit advertisement for a given link where the Application Identifier Bit
Mask identifies all the applications that are making use of the value Mask identifies all the applications that are making use of the value
for that link. for that link.
It is also possible to advertise the same value for a given link It is also possible to advertise the same value for a given link
multiple times with disjoint sets of applications specified in the multiple times with disjoint sets of applications specified in the
Application Identifier Bit Mask. This is less efficient but still Application Identifier Bit Mask. This is less efficient but still
valid. valid.
It is also possible to advertise a single advertisement with zero- It is also possible to advertise a single advertisement with a zero-
length SABM and UDABM so long as the constraints discussed in length SABM and UDABM so long as the constraints discussed in
Sections 4.2 and 6.2 are acceptable. Sections 4.2 and 6.2 are satisfied.
If different values for maximum link bandwidth for a given link are If different values for maximum link bandwidth for a given link are
advertised, all values MUST be ignored. advertised, all values MUST be ignored.
4.2.2. Special Considerations for Reservable/Unreserved Bandwidth 4.2.2. Special Considerations for Reservable/Unreserved Bandwidth
Maximum reservable link bandwidth and unreserved bandwidth are Maximum reservable link bandwidth and unreserved bandwidth are
attributes specific to RSVP-TE. When advertised using the attributes specific to RSVP-TE. When advertised using the
Application-Specific Link Attributes sub-TLV, bits other than the Application-Specific Link Attributes sub-TLV, bits other than the
RSVP-TE (R-bit) MUST NOT be set in the Application Identifier Bit RSVP-TE bit (R-bit) MUST NOT be set in the Application Identifier Bit
Mask. If an advertisement of maximum reservable link bandwidth or Mask. If an advertisement of maximum reservable link bandwidth or
unreserved bandwidth is received with bits other than the RSVP-TE bit unreserved bandwidth is received with bits other than the R-bit set,
set, the advertisement MUST be ignored. the advertisement MUST be ignored.
4.2.3. Considerations for Extended TE Metrics 4.2.3. Considerations for Extended TE Metrics
[RFC8570] defines a number of dynamic performance metrics associated [RFC8570] defines a number of dynamic performance metrics associated
with a link. It is conceivable that such metrics could be measured with a link. It is conceivable that such metrics could be measured
specific to traffic associated with a specific application. specific to traffic associated with a specific application.
Therefore, this document includes support for advertising these link Therefore, this document includes support for advertising these link
attributes specific to a given application. However, in practice, it attributes specific to a given application. However, in practice, it
may well be more practical to have these metrics reflect the may well be more practical to have these metrics reflect the
performance of all traffic on the link regardless of application. In performance of all traffic on the link regardless of application. In
such cases, advertisements for these attributes will be associated such cases, advertisements for these attributes will be associated
with all of the applications utilizing that link. This can be done with all of the applications utilizing that link. This can be done
either by explicitly specifying the applications in the Application by either explicitly specifying the applications in the Application
Identifier Bit Mask or by using a zero-length Application Identifier Identifier Bit Mask or using a zero-length Application Identifier Bit
Bit Mask. The use of zero-length Application Identifier Bit Mask is Mask. The use of zero-length Application Identifier Bit Masks is
further discussed in Section 6.2. further discussed in Section 6.2.
4.3. Application-Specific SRLG TLV 4.3. Application-Specific SRLG TLV
A new TLV is defined to advertise application-specific SRLGs for a A TLV is defined to advertise application-specific SRLGs for a given
given link. Although similar in functionality to TLV 138 [RFC5307] link. Although similar in functionality to TLV 138 [RFC5307] and TLV
and TLV 139 [RFC6119], a single TLV provides support for IPv4, IPv6, 139 [RFC6119], this single TLV provides support for IPv4, IPv6, and
and unnumbered identifiers for a link. Unlike TLVs 138 and 139, it unnumbered identifiers for a link. Unlike TLVs 138 and 139, it
utilizes sub-TLVs to encode the link identifiers in order to provide utilizes sub-TLVs to encode the link identifiers in order to provide
the flexible formatting required to support multiple link identifier the flexible formatting required to support multiple link identifier
types. types.
Type: 238 Type:
238
Length: Number of octets in the value field (1 octet) Length:
Number of octets in the value field (1 octet)
Value: Value:
Neighbor System-ID + pseudonode ID (7 octets) Neighbor System-ID + pseudonode ID (7 octets)
Application Identifier Bit Mask (as defined in Section 4.1) Application Identifier Bit Mask (as defined in Section 4.1)
Length of sub-TLVs (1 octet) Length of sub-TLVs (1 octet)
Link Identifier sub-TLVs (variable) Link Identifier sub-TLVs (variable)
0 or more SRLG values (each value is 4 octets) 0 or more SRLG values (each value is 4 octets)
If the SABM or UDABM Length in the Application Identifier Bit Mask is If the SABM Length or UDABM Length in the Application Identifier Bit
greater than 8, the entire sub-TLV MUST be ignored. Mask is greater than 8, the entire sub-TLV MUST be ignored.
When SABM or UDABM Length is non-zero and the L-flag is NOT set, all When the SABM Length or UDABM Length is non-zero and the L-flag is
applications specified in the bit mask MUST use SRLG advertisements NOT set, all applications specified in the bit mask MUST use SRLG
in the Application-Specific SRLG TLV. advertisements in the Application-Specific SRLG TLV.
The following Link Identifier sub-TLVs are defined. The values The following Link Identifier sub-TLVs are defined. The values
chosen intentionally match the equivalent sub-TLVs from [RFC5305], chosen intentionally match the equivalent sub-TLVs from [RFC5305],
[RFC5307], and [RFC6119]. [RFC5307], and [RFC6119].
+======+=========================================+ +======+=========================================+
| Type | Description | | Type | Description |
+======+=========================================+ +======+=========================================+
| 4 | Link Local/Remote Identifiers [RFC5307] | | 4 | Link Local/Remote Identifiers [RFC5307] |
+------+-----------------------------------------+ +------+-----------------------------------------+
skipping to change at page 13, line 22 skipping to change at line 580
used by the set of applications specified in the Application used by the set of applications specified in the Application
Identifier Bit Mask. Identifier Bit Mask.
For a given application, the setting of the L-flag MUST be the same For a given application, the setting of the L-flag MUST be the same
in all TLVs for a given link. In cases where this constraint is in all TLVs for a given link. In cases where this constraint is
violated, the L-flag MUST be considered set for this application. violated, the L-flag MUST be considered set for this application.
5. Attribute Advertisements and Enablement 5. Attribute Advertisements and Enablement
This document defines extensions to support the advertisement of This document defines extensions to support the advertisement of
application-specific link attributes. ASLAs.
Whether the presence of link attribute advertisements for a given Whether the presence of link attribute advertisements for a given
application indicates that the application is enabled on that link application indicates that the application is enabled on that link
depends upon the application. Similarly, whether the absence of link depends upon the application. Similarly, whether the absence of link
attribute advertisements indicates that the application is not attribute advertisements indicates that the application is not
enabled depends upon the application. enabled depends upon the application.
In the case of RSVP-TE, the advertisement of application-specific In the case of RSVP-TE, the advertisement of ASLAs implies that RSVP
link attributes implies that RSVP is enabled on that link. The is enabled on that link. The absence of RSVP-TE ASLAs in combination
absence of RSVP-TE application-specific link attributes in with the absence of legacy advertisements implies that RSVP is not
combination with the absence of legacy advertisements implies that enabled on that link.
RSVP is not enabled on that link.
In the case of SR Policy, the advertisement of application-specific In the case of SR Policy, the advertisement of ASLAs does not
link attributes does not indicate enablement of SR Policy on that indicate enablement of SR Policy on that link. The advertisements
link. The advertisements are only used to support constraints that are only used to support constraints that may be applied when
may be applied when specifying an explicit path. SR Policy is specifying an explicit path. SR Policy is implicitly enabled on all
implicitly enabled on all links that are part of the SR-enabled links that are part of the SR-enabled topology independent of the
topology independent of the existence of link attribute existence of link attribute advertisements.
advertisements.
In the case of LFA, the advertisement of application-specific link In the case of LFA, the advertisement of ASLAs does not indicate
attributes does not indicate enablement of LFA on that link. enablement of LFA on that link. Enablement is controlled by local
Enablement is controlled by local configuration. configuration.
In the future, if additional standard applications are defined to use In the future, if additional standard applications are defined to use
this mechanism, the specification defining this use MUST define the this mechanism, the specification defining this use MUST define the
relationship between application-specific link attribute relationship between ASLA advertisements and enablement for those
advertisements and enablement for that application. applications.
This document allows the advertisement of application-specific link This document allows the advertisement of ASLAs with no application
attributes with no application identifiers, i.e., both the Standard identifiers, i.e., neither the Standard Application Identifier Bit
Application Identifier Bit Mask and the User-Defined Application Mask nor the User-Defined Application Identifier Bit Mask is present
Identifier Bit Mask are not present (see Section 4.1). This supports (see Section 4.1). This supports the use of the link attribute by
the use of the link attribute by any application. In the presence of any application. In the presence of an application where the
an application where the advertisement of link attribute advertisement of link attributes is used to infer the enablement of
advertisements is used to infer the enablement of an application on an application on that link (e.g., RSVP-TE), the absence of the
that link (e.g., RSVP-TE), the absence of the application identifier application identifier leaves ambiguous whether that application is
leaves ambiguous whether that application is enabled on such a link. enabled on such a link. This needs to be considered when making use
This needs to be considered when making use of the "any application" of the "any application" encoding.
encoding.
6. Deployment Considerations 6. Deployment Considerations
This section discusses deployment considerations associated with the This section discusses deployment considerations associated with the
use of application-specific link attribute advertisements. use of ASLA advertisements.
6.1. Use of Legacy Advertisements 6.1. Use of Legacy Advertisements
Bit identifiers for standard applications are defined in Section 4.1. Bit identifiers for standard applications are defined in Section 4.1.
All of the identifiers defined in this document are associated with All of the identifiers defined in this document are associated with
applications that were already deployed in some networks prior to the applications that were already deployed in some networks prior to the
writing of this document. Therefore, such applications have been writing of this document. Therefore, such applications have been
deployed using the legacy advertisements. The standard applications deployed using the legacy advertisements. The standard applications
defined in this document may continue to use legacy advertisements defined in this document may continue to use legacy advertisements
for a given link so long as at least one of the following conditions for a given link so long as at least one of the following conditions
skipping to change at page 15, line 14 skipping to change at line 664
New applications that future documents define to make use of the New applications that future documents define to make use of the
advertisements defined in this document MUST NOT make use of legacy advertisements defined in this document MUST NOT make use of legacy
advertisements. This simplifies deployment of new applications by advertisements. This simplifies deployment of new applications by
eliminating the need to support multiple ways to advertise attributes eliminating the need to support multiple ways to advertise attributes
for the new applications. for the new applications.
6.2. Use of Zero-Length Application Identifier Bit Masks 6.2. Use of Zero-Length Application Identifier Bit Masks
Link attribute advertisements associated with zero-length Application Link attribute advertisements associated with zero-length Application
Identifier Bit Masks for both standard applications and user-defined Identifier Bit Masks for both standard applications and UDAs are
applications are usable by any application, subject to the usable by any application, subject to the restrictions specified in
restrictions specified in Section 4.2. If support for a new Section 4.2. If support for a new application is introduced on any
application is introduced on any node in a network in the presence of node in a network in the presence of such advertisements, the new
such advertisements, the new application will use these application will use these advertisements, when the aforementioned
advertisements, when the aforementioned restrictions are met. If restrictions are met. If this is not what is intended, then existing
this is not what is intended, then existing link attribute link attribute advertisements MUST be readvertised with an explicit
advertisements MUST be readvertised with an explicit set of set of applications specified before a new application is introduced.
applications specified before a new application is introduced.
6.3. Interoperability, Backwards Compatibility, and Migration Concerns 6.3. Interoperability, Backwards Compatibility, and Migration Concerns
Existing deployments of RSVP-TE, SR Policy, and/or LFA utilize the Existing deployments of RSVP-TE, SR Policy, and/or LFA utilize the
legacy advertisements listed in Section 3. Routers that do not legacy advertisements listed in Section 3. Routers that do not
support the extensions defined in this document will only process support the extensions defined in this document will only process
legacy advertisements and are likely to infer that RSVP-TE is enabled legacy advertisements and are likely to infer that RSVP-TE is enabled
on the links for which legacy advertisements exist. It is expected on the links for which legacy advertisements exist. It is expected
that deployments using the legacy advertisements will persist for a that deployments using the legacy advertisements will persist for a
significant period of time. Therefore, deployments using the significant period of time. Therefore, deployments using the
skipping to change at page 16, line 27 skipping to change at line 720
advertised attributes on a link and to cases where RSVP-TE is using advertised attributes on a link and to cases where RSVP-TE is using
some link attribute advertisements on the link but some link some link attribute advertisements on the link but some link
attributes cannot be shared with RSVP-TE. attributes cannot be shared with RSVP-TE.
6.3.3. Interoperability with Legacy Routers 6.3.3. Interoperability with Legacy Routers
For the standard applications defined in this document, routers that For the standard applications defined in this document, routers that
do not support the extensions defined in this document will send and do not support the extensions defined in this document will send and
receive only legacy link attribute advertisements. In addition, the receive only legacy link attribute advertisements. In addition, the
link attribute values associated with these applications are always link attribute values associated with these applications are always
shared since legacy routers have no way of advertising or processing shared, since legacy routers have no way of advertising or processing
application-specific values. So long as there is any legacy router application-specific values. So long as there is any legacy router
in the network that has any of the standard applications defined in in the network that has any of the standard applications defined in
this document enabled, all routers MUST continue to advertise link this document enabled, all routers MUST continue to advertise link
attributes for these applications using only legacy advertisements. attributes for these applications using only legacy advertisements.
ASLA advertisements for these applications MUST NOT be sent. Once ASLA advertisements for these applications MUST NOT be sent. Once
all legacy routers have been upgraded, migration from legacy all legacy routers have been upgraded, migration from legacy
advertisements to ASLA advertisements can be achieved via the advertisements to ASLA advertisements can be achieved via the
following steps: following steps:
1) Send ASLA advertisements while continuing to advertise using 1. Send ASLA advertisements while continuing to advertise legacy
legacy (all advertisements are then duplicated). Receiving advertisements (all advertisements are then duplicated).
routers continue to use legacy advertisements. Receiving routers continue to use legacy advertisements.
2) Enable the use of the ASLA advertisements on all routers. 2. Enable the use of the ASLA advertisements on all routers.
3) Remove legacy advertisements. 3. Remove legacy advertisements.
When the migration is complete, it then becomes possible to advertise When the migration is complete, it then becomes possible to advertise
incongruent values per application on a given link. incongruent values per application on a given link.
Note that the use of the L-flag is of no value in the migration. Note that the use of the L-flag is of no value in the migration.
Documents defining new applications that make use of the application- Documents defining new applications that make use of the application-
specific advertisements defined in this document MUST discuss specific advertisements defined in this document MUST discuss
interoperability and backwards-compatibility issues that could occur interoperability and backwards-compatibility issues that could occur
in the presence of routers that do not support the new application. in the presence of routers that do not support the new application.
6.3.4. Use of Application-Specific Advertisements for RSVP-TE 6.3.4. Use of Application-Specific Advertisements for RSVP-TE
The extensions defined in this document include RSVP-TE as one of the The extensions defined in this document include RSVP-TE as one of the
applications. It is therefore possible, in the future, for applications. It is therefore possible, in the future, for
implementations to migrate to the use of application-specific implementations to migrate to the use of application-specific
advertisements in support of RSVP-TE. This could be done in the advertisements in support of RSVP-TE. This could be done in the
following stepwise manner: following stepwise manner:
1) Upgrade all routers to support the extensions in this document. 1. Upgrade all routers to support the extensions in this document.
2) Advertise all legacy link attributes using ASLA advertisements 2. Advertise all legacy link attributes using ASLA advertisements
with the L-flag clear and R-bit set. At this point, both legacy with the L-flag clear and the R-bit set. At this point, both
and application-specific advertisements are being sent. legacy and application-specific advertisements are being sent.
3) Remove legacy advertisements. 3. Remove legacy advertisements.
7. IANA Considerations 7. IANA Considerations
This section lists the protocol codepoint changes introduced by this This section lists the protocol codepoint changes introduced by this
document and the related updates made by IANA. document and the related IANA updates.
For the new registries defined under the "IS-IS TLV Codepoints" For the registries defined under the "IS-IS TLV Codepoints" group of
registry with the "Expert Review" registration procedure (see registries with a registration procedure of "Expert Review" (see
Sections 7.3 and 7.5), guidance for designated experts can be found Sections 7.3 and 7.5), guidance for designated experts can be found
in [RFC7370]. in [RFC7370].
Note that in all cases where the current registry reference is to RFC Note that in all cases where the registry reference was to RFC 8919,
8919 the registry should be updated to this document. the registry has been updated to refer to this document.
7.1. Application-Specific Link Attributes Sub-TLV 7.1. Application-Specific Link Attributes Sub-TLV
IANA has registered the new sub-TLV defined in Section 4.2 in the IANA has registered the sub-TLV defined in Section 4.2 in the "IS-IS
"IS-IS Sub-TLVs for TLVs Advertising Neighbor Information" registry. Sub-TLVs for TLVs Advertising Neighbor Information" registry.
+======+======================+====+====+======+=====+=====+=====+ +======+======================+====+====+======+=====+=====+=====+
| Type | Description | 22 | 23 | 25 | 141 | 222 | 223 | | Type | Description | 22 | 23 | 25 | 141 | 222 | 223 |
+======+======================+====+====+======+=====+=====+=====+ +======+======================+====+====+======+=====+=====+=====+
| 16 | Application-Specific | y | y | y(s) | y | y | y | | 16 | Application-Specific | y | y | y(s) | y | y | y |
| | Link Attributes | | | | | | | | | Link Attributes | | | | | | |
+------+----------------------+----+----+------+-----+-----+-----+ +------+----------------------+----+----+------+-----+-----+-----+
Table 3 Table 3
7.2. Application-Specific SRLG TLV 7.2. Application-Specific SRLG TLV
IANA has registered the new TLV defined in Section 4.3 in the "IS-IS IANA has registered the TLV defined in Section 4.3 in the "IS-IS Top-
Top-Level TLV Codepoints" registry. Level TLV Codepoints" registry.
+=======+===========================+=====+=====+=====+=======+ +=======+===========================+=====+=====+=====+=======+
| Value | Description | IIH | LSP | SNP | Purge | | Value | Description | IIH | LSP | SNP | Purge |
+=======+===========================+=====+=====+=====+=======+ +=======+===========================+=====+=====+=====+=======+
| 238 | Application-Specific SRLG | n | y | n | n | | 238 | Application-Specific SRLG | n | y | n | n |
+-------+---------------------------+-----+-----+-----+-------+ +-------+---------------------------+-----+-----+-----+-------+
Table 4 Table 4
7.3. Sub-sub-TLV Codepoints for Application-Specific Link Attributes 7.3. IS-IS Sub-Sub-TLV Codepoints for Application-Specific Link
Registry Attributes Registry
IANA has created a new registry titled "IS-IS Sub-sub-TLV Codepoints IANA has created a registry titled "IS-IS Sub-Sub-TLV Codepoints for
for Application-Specific Link Attributes" under the "IS-IS TLV Application-Specific Link Attributes" under the "IS-IS TLV
Codepoints" registry to control the assignment of sub-sub-TLV Codepoints" registry to control the assignment of sub-sub-TLV
codepoints for the Application-Specific Link Attributes sub-TLV codepoints for the Application-Specific Link Attributes sub-TLV
defined in Section 7.1. The registration procedure is "Expert defined in Section 7.1. The registration procedure is "Expert
Review" as defined in [RFC8126]. The initial contents of this Review" as defined in [RFC8126]. The initial contents of this
registry are as follows: registry are as follows:
+========+====================================+===========+ +========+====================================+===========+
| Type | Description | Reference | | Type | Description | Reference |
+========+====================================+===========+ +========+====================================+===========+
| 0-2 | Unassigned | | | 0-2 | Unassigned | |
skipping to change at page 19, line 26 skipping to change at line 836
| 10 | Maximum reservable link bandwidth | [RFC5305] | | 10 | Maximum reservable link bandwidth | [RFC5305] |
+--------+------------------------------------+-----------+ +--------+------------------------------------+-----------+
| 11 | Unreserved bandwidth | [RFC5305] | | 11 | Unreserved bandwidth | [RFC5305] |
+--------+------------------------------------+-----------+ +--------+------------------------------------+-----------+
| 12-13 | Unassigned | | | 12-13 | Unassigned | |
+--------+------------------------------------+-----------+ +--------+------------------------------------+-----------+
| 14 | Extended Administrative Group | [RFC7308] | | 14 | Extended Administrative Group | [RFC7308] |
+--------+------------------------------------+-----------+ +--------+------------------------------------+-----------+
| 15-17 | Unassigned | | | 15-17 | Unassigned | |
+--------+------------------------------------+-----------+ +--------+------------------------------------+-----------+
| 18 | TE Default Metric | [RFC5305] | | 18 | TE Default metric | [RFC5305] |
+--------+------------------------------------+-----------+ +--------+------------------------------------+-----------+
| 19-32 | Unassigned | | | 19-32 | Unassigned | |
+--------+------------------------------------+-----------+ +--------+------------------------------------+-----------+
| 33 | Unidirectional Link Delay | [RFC8570] | | 33 | Unidirectional Link Delay | [RFC8570] |
+--------+------------------------------------+-----------+ +--------+------------------------------------+-----------+
| 34 | Min/Max Unidirectional Link Delay | [RFC8570] | | 34 | Min/Max Unidirectional Link Delay | [RFC8570] |
+--------+------------------------------------+-----------+ +--------+------------------------------------+-----------+
| 35 | Unidirectional Delay Variation | [RFC8570] | | 35 | Unidirectional Delay Variation | [RFC8570] |
+--------+------------------------------------+-----------+ +--------+------------------------------------+-----------+
| 36 | Unidirectional Link Loss | [RFC8570] | | 36 | Unidirectional Link Loss | [RFC8570] |
skipping to change at page 20, line 11 skipping to change at line 867
Table 5 Table 5
IANA has also added the following notes to this registry: IANA has also added the following notes to this registry:
Note: For future codepoints, in cases where the document that Note: For future codepoints, in cases where the document that
defines the encoding is different from the document that assigns defines the encoding is different from the document that assigns
the codepoint, the encoding reference MUST be to the document that the codepoint, the encoding reference MUST be to the document that
defines the encoding. defines the encoding.
Note: If a link attribute can be advertised both as a sub-TLV of Note: If a link attribute can be advertised both as a sub-TLV of
TLVs Advertising Neighbor Information and as a sub-sub-TLV of the TLVs advertising neighbor information and as a sub-sub-TLV of the
Application-Specific Link Attributes sub-TLV defined in RFC 8919, Application-Specific Link Attributes sub-TLV defined in RFC 9479,
then the same numerical code should be assigned to the link then the same numerical code should be assigned to the link
attribute whenever possible. attribute whenever possible.
7.4. Link Attribute Application Identifiers Registry 7.4. Link Attribute Application Identifiers Registry
IANA has created a new registry titled "Link Attribute Application IANA has created a registry titled "Link Attribute Application
Identifiers" under the "Interior Gateway Protocol (IGP) Parameters" Identifiers" within the "Interior Gateway Protocol (IGP) Parameters"
registry to control the assignment of Application Identifier Bits. group of registries to control the assignment of Application
The registration policy for this registry is "Expert Review" as Identifier Bits. The registration policy for this registry is
defined in [RFC8126]. Bit definitions SHOULD be assigned such that "Expert Review" as defined in [RFC8126]. Bit definitions SHOULD be
all bits in the lowest available octet are allocated before assigning assigned such that all bits in the lowest available octet are
bits in the next octet. This minimizes the number of octets that allocated before assigning bits in the next octet. This minimizes
will need to be transmitted. The initial contents of this registry the number of octets that will need to be transmitted. The initial
are as follows: contents of this registry are as follows:
+=======+================================+ +======+================================+
| Bit # | Name | | Bit | Name |
+=======+================================+ +======+================================+
| 0 | RSVP-TE (R-bit) | | 0 | RSVP-TE (R-bit) |
+-------+--------------------------------+ +------+--------------------------------+
| 1 | Segment Routing Policy (S-bit) | | 1 | Segment Routing Policy (S-bit) |
+-------+--------------------------------+ +------+--------------------------------+
| 2 | Loop-Free Alternate (F-bit) | | 2 | Loop-Free Alternate (F-bit) |
+-------+--------------------------------+ +------+--------------------------------+
| 3-63 | Unassigned | | 3-63 | Unassigned |
+-------+--------------------------------+ +------+--------------------------------+
Table 6 Table 6
7.5. Sub-TLVs for TLV 238 Registry 7.5. IS-IS Sub-TLVs for Application-Specific SRLG TLV
IANA has created a new registry titled "IS-IS Sub-TLVs for IANA has created a registry titled "IS-IS Sub-TLVs for Application-
Application-Specific SLRG TLV" under the "IS-IS TLV Codepoints" Specific SRLG TLV" under the "IS-IS TLV Codepoints" registry to
registry to control the assignment of sub-TLV types for the control the assignment of sub-TLV types for the Application-Specific
Application-Specific SRLG TLV. The registration procedure is "Expert SRLG TLV (TLV 238). The registration procedure is "Expert Review" as
Review" as defined in [RFC8126]. The initial contents of this defined in [RFC8126]. The initial contents of this registry are as
registry are as follows: follows:
+========+===============================+===========+ +========+===============================+===========+
| Value | Description | Reference | | Value | Description | Reference |
+========+===============================+===========+ +========+===============================+===========+
| 0-3 | Unassigned | | | 0-3 | Unassigned | |
+--------+-------------------------------+-----------+ +--------+-------------------------------+-----------+
| 4 | Link Local/Remote Identifiers | [RFC5307] | | 4 | Link Local/Remote Identifiers | [RFC5307] |
+--------+-------------------------------+-----------+ +--------+-------------------------------+-----------+
| 5 | Unassigned | | | 5 | Unassigned | |
+--------+-------------------------------+-----------+ +--------+-------------------------------+-----------+
skipping to change at page 21, line 47 skipping to change at line 949
8. Security Considerations 8. Security Considerations
Security concerns for IS-IS are addressed in [ISO10589], [RFC5304], Security concerns for IS-IS are addressed in [ISO10589], [RFC5304],
and [RFC5310]. While IS-IS is deployed under a single administrative and [RFC5310]. While IS-IS is deployed under a single administrative
domain, there can be deployments where potential attackers have domain, there can be deployments where potential attackers have
access to one or more networks in the IS-IS routing domain. In these access to one or more networks in the IS-IS routing domain. In these
deployments, the stronger authentication mechanisms defined in the deployments, the stronger authentication mechanisms defined in the
aforementioned documents SHOULD be used. aforementioned documents SHOULD be used.
This document defines a new way to advertise link attributes. This document defines an improved way to advertise link attributes.
Tampering with the information defined in this document may have an Tampering with the information defined in this document may have an
effect on applications using it, including impacting traffic effect on applications using it, including impacting TE as discussed
engineering as discussed in [RFC8570]. As the advertisements defined in [RFC8570]. As the advertisements defined in this document limit
in this document limit the scope to specific applications, the impact the scope to specific applications, the impact of tampering is
of tampering is similarly limited in scope. similarly limited in scope.
9. Changes to RFC 8919 9. Changes to RFC 8919
Discussion within the LSR WG indicated that there was confusion Discussion within the LSR WG indicated that there was confusion
regarding the use of ASLA advertisements that had a zero length SABM/ regarding the use of ASLA advertisements that had a zero-length SABM/
UDABM. The discussion can be seen by searching the LSR WG mailing UDABM. The discussion can be seen by searching the LSR WG mailing
list archives for the thread "Proposed Errata for RFCs 8919/8920" list archives for the thread "Proposed Errata for RFCs 8919/8920"
starting on 15 June 2021. starting on 15 June 2021.
Changes to Sections 4.2, 4.3, and 6.2 have been introduced to clarify Changes to Sections 4.2, 4.3, and 6.2 have been introduced to clarify
normative behavior in the presence of such advertisements. In normative behavior in the presence of such advertisements. In
particular, the text in RFC 8919 used the word "permitted", particular, the text in [RFC8919] used the word "permitted",
suggesting that the use of such advertisements is "optional". Such suggesting that the use of such advertisements is "optional". Such
an interpretation could lead to interoperability issues and is not an interpretation could lead to interoperability issues and is not
what was intended. what was intended.
The replacement text makes explicit the specific conditions when such The replacement text makes explicit the specific conditions when such
advertisements MUST be used and the specific conditions under which advertisements MUST be used and the specific conditions under which
they MUST NOT be used. they MUST NOT be used.
10. References 10. References
10.1. Normative References 10.1. Normative References
[ISO10589] ISO, "Information technology - Telecommunications and [ISO10589] ISO, "Information technology - Telecommunications and
information exchange between systems - Intermediate System information exchange between systems - Intermediate System
to Intermediate System intra-domain routing information to Intermediate System intra-domain routing information
exchange protocol for use in conjunction with the protocol exchange protocol for use in conjunction with the protocol
for providing the connectionless-mode network service (ISO for providing the connectionless-mode network service (ISO
8473)", ISO/IEC 10589:2002, Second Edition, November 2002. 8473)", Second Edition, ISO/IEC 10589:2002, November 2002,
<https://www.iso.org/standard/30932.html>.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997, DOI 10.17487/RFC2119, March 1997,
<https://www.rfc-editor.org/info/rfc2119>. <https://www.rfc-editor.org/info/rfc2119>.
[RFC5304] Li, T. and R. Atkinson, "IS-IS Cryptographic [RFC5304] Li, T. and R. Atkinson, "IS-IS Cryptographic
Authentication", RFC 5304, DOI 10.17487/RFC5304, October Authentication", RFC 5304, DOI 10.17487/RFC5304, October
2008, <https://www.rfc-editor.org/info/rfc5304>. 2008, <https://www.rfc-editor.org/info/rfc5304>.
skipping to change at page 24, line 11 skipping to change at line 1055
IP Fast Reroute: Loop-Free Alternates", RFC 5286, IP Fast Reroute: Loop-Free Alternates", RFC 5286,
DOI 10.17487/RFC5286, September 2008, DOI 10.17487/RFC5286, September 2008,
<https://www.rfc-editor.org/info/rfc5286>. <https://www.rfc-editor.org/info/rfc5286>.
[RFC7855] Previdi, S., Ed., Filsfils, C., Ed., Decraene, B., [RFC7855] Previdi, S., Ed., Filsfils, C., Ed., Decraene, B.,
Litkowski, S., Horneffer, M., and R. Shakir, "Source Litkowski, S., Horneffer, M., and R. Shakir, "Source
Packet Routing in Networking (SPRING) Problem Statement Packet Routing in Networking (SPRING) Problem Statement
and Requirements", RFC 7855, DOI 10.17487/RFC7855, May and Requirements", RFC 7855, DOI 10.17487/RFC7855, May
2016, <https://www.rfc-editor.org/info/rfc7855>. 2016, <https://www.rfc-editor.org/info/rfc7855>.
[SEGMENT-ROUTING] [RFC8919] Ginsberg, L., Psenak, P., Previdi, S., Henderickx, W., and
Filsfils, C., Talaulikar, K., Voyer, D., Bogdanov, A., and J. Drake, "IS-IS Application-Specific Link Attributes",
P. Mattes, "Segment Routing Policy Architecture", RFC 8919, DOI 10.17487/RFC8919, October 2020,
RFC 9256, DOI 10.17487/RFC9256, <https://www.rfc-editor.org/info/rfc8919>.
<https://www.rfc-editor.org/rfc/rfc9256>.
[RFC9256] Filsfils, C., Talaulikar, K., Ed., Voyer, D., Bogdanov,
A., and P. Mattes, "Segment Routing Policy Architecture",
RFC 9256, DOI 10.17487/RFC9256, July 2022,
<https://www.rfc-editor.org/info/rfc9256>.
Acknowledgements Acknowledgements
RFC 8919 included the following acknowledgements: RFC 8919 included the following acknowledgements:
Eric Rosen and Acee Lindem for their careful review and content | Eric Rosen and Acee Lindem for their careful review and content
suggestions. | suggestions.
For the new version, the authors would like to thank Bruno Decraene. For the new version (this document), the authors would like to thank
Bruno Decraene.
Authors' Addresses Authors' Addresses
Les Ginsberg Les Ginsberg
Cisco Systems Cisco Systems
United States of America United States of America
Email: ginsberg@cisco.com Email: ginsberg@cisco.com
Peter Psenak Peter Psenak
Cisco Systems Cisco Systems
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