draft-ietf-isis-te-app-17.txt   draft-ietf-isis-te-app-18.txt 
Networking Working Group L. Ginsberg Networking Working Group L. Ginsberg
Internet-Draft P. Psenak Internet-Draft P. Psenak
Intended status: Standards Track Cisco Systems Intended status: Standards Track Cisco Systems
Expires: December 19, 2020 S. Previdi Expires: December 24, 2020 S. Previdi
Huawei Huawei
W. Henderickx W. Henderickx
Nokia Nokia
J. Drake J. Drake
Juniper Networks Juniper Networks
June 17, 2020 June 22, 2020
IS-IS TE Attributes per application IS-IS Application-Specific Link Attributes
draft-ietf-isis-te-app-17 draft-ietf-isis-te-app-18
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, Loop Free Alternate) that also make use of Segment Routing Policy, Loop Free Alternate) that also make use of
the link attribute advertisements have been defined . In cases where the link attribute advertisements have been defined . In cases where
multiple applications wish to make use of these link attributes, the multiple applications wish to make use of these link attributes, the
current advertisements do not support application specific values for current advertisements do not support application-specific values for
a given attribute, nor do they support indication of which a given attribute, nor do they support indication of which
applications are using the advertised value for a given link. This applications are using the advertised value for a given link. This
document introduces new link attribute advertisements that address document introduces new link attribute advertisements that address
both of these shortcomings. both of these shortcomings.
Requirements Language Requirements Language
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
"OPTIONAL" in this document are to be interpreted as described in BCP "OPTIONAL" in this document are to be interpreted as described in BCP
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Internet-Drafts are working documents of the Internet Engineering Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet- working documents as Internet-Drafts. The list of current Internet-
Drafts is at https://datatracker.ietf.org/drafts/current/. Drafts is at https://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress." material or to cite them other than as "work in progress."
This Internet-Draft will expire on December 19, 2020. This Internet-Draft will expire on December 24, 2020.
Copyright Notice Copyright Notice
Copyright (c) 2020 IETF Trust and the persons identified as the Copyright (c) 2020 IETF Trust and the persons identified as the
document authors. All rights reserved. document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents Provisions Relating to IETF Documents
(https://trustee.ietf.org/license-info) in effect on the date of (https://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents publication of this document. Please review these documents
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the Trust Legal Provisions and are provided without warranty as the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License. described in the Simplified BSD License.
Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Requirements Discussion . . . . . . . . . . . . . . . . . . . 4 2. Requirements Discussion . . . . . . . . . . . . . . . . . . . 4
3. Legacy Advertisements . . . . . . . . . . . . . . . . . . . . 5 3. Legacy Advertisements . . . . . . . . . . . . . . . . . . . . 5
3.1. Legacy sub-TLVs . . . . . . . . . . . . . . . . . . . . . 5 3.1. Legacy sub-TLVs . . . . . . . . . . . . . . . . . . . . . 5
3.2. Legacy SRLG Advertisements . . . . . . . . . . . . . . . 6 3.2. Legacy SRLG Advertisements . . . . . . . . . . . . . . . 6
4. Advertising Application Specific Link Attributes . . . . . . 6 4. Advertising Application-Specific Link Attributes . . . . . . 6
4.1. Application Identifier Bit Mask . . . . . . . . . . . . . 6 4.1. Application Identifier Bit Mask . . . . . . . . . . . . . 6
4.2. Application Specific Link Attributes sub-TLV . . . . . . 9 4.2. Application-Specific Link Attributes sub-TLV . . . . . . 9
4.2.1. Special Considerations for Maximum Link Bandwidth . . 10 4.2.1. Special Considerations for Maximum Link Bandwidth . . 10
4.2.2. Special Considerations for Reservable/Unreserved 4.2.2. Special Considerations for Reservable/Unreserved
Bandwidth . . . . . . . . . . . . . . . . . . . . . . 10 Bandwidth . . . . . . . . . . . . . . . . . . . . . . 10
4.2.3. Considerations for Extended TE Metrics . . . . . . . 11 4.2.3. Considerations for Extended TE Metrics . . . . . . . 11
4.3. Application Specific SRLG TLV . . . . . . . . . . . . . . 11 4.3. Application-Specific SRLG TLV . . . . . . . . . . . . . . 11
5. Attribute Advertisements and Enablement . . . . . . . . . . . 12 5. Attribute Advertisements and Enablement . . . . . . . . . . . 12
6. Deployment Considerations . . . . . . . . . . . . . . . . . . 13 6. Deployment Considerations . . . . . . . . . . . . . . . . . . 13
6.1. Use of Legacy Advertisements . . . . . . . . . . . . . . 13 6.1. Use of Legacy Advertisements . . . . . . . . . . . . . . 13
6.2. Use of Zero Length Application Identifier Bit Masks . . . 14 6.2. Use of Zero Length Application Identifier Bit Masks . . . 14
6.3. Interoperability, Backwards Compatibility and Migration 6.3. Interoperability, Backwards Compatibility and Migration
Concerns . . . . . . . . . . . . . . . . . . . . . . . . 14 Concerns . . . . . . . . . . . . . . . . . . . . . . . . 14
6.3.1. Multiple Applications: Common Attributes with RSVP- 6.3.1. Multiple Applications: Common Attributes with RSVP-
TE . . . . . . . . . . . . . . . . . . . . . . . . . 15 TE . . . . . . . . . . . . . . . . . . . . . . . . . 15
6.3.2. Multiple Applications: All Attributes Not Shared with 6.3.2. Multiple Applications: All Attributes Not Shared with
RSVP-TE . . . . . . . . . . . . . . . . . . . . . . . 15 RSVP-TE . . . . . . . . . . . . . . . . . . . . . . . 15
6.3.3. Interoperability with Legacy Routers . . . . . . . . 15 6.3.3. Interoperability with Legacy Routers . . . . . . . . 15
6.3.4. Use of Application Specific Advertisements for RSVP- 6.3.4. Use of Application-Specific Advertisements for RSVP-
TE . . . . . . . . . . . . . . . . . . . . . . . . . 16 TE . . . . . . . . . . . . . . . . . . . . . . . . . 16
7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 16 7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 16
7.1. Application Specific Link Attributes sub-TLV . . . . . . 17 7.1. Application-Specific Link Attributes sub-TLV . . . . . . 17
7.2. Application Specific SRLG TLV . . . . . . . . . . . . . . 17 7.2. Application-Specific SRLG TLV . . . . . . . . . . . . . . 17
7.3. Application Specific Link Attributes sub-sub-TLV Registry 17 7.3. Application-Specific Link Attributes sub-sub-TLV Registry 17
7.4. Link Attribute Application Identifier Registry . . . . . 18 7.4. Link Attribute Application Identifier Registry . . . . . 18
7.5. SRLG sub-TLVs . . . . . . . . . . . . . . . . . . . . . . 19 7.5. SRLG sub-TLVs . . . . . . . . . . . . . . . . . . . . . . 19
8. Security Considerations . . . . . . . . . . . . . . . . . . . 19 8. Security Considerations . . . . . . . . . . . . . . . . . . . 19
9. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 20 9. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 20
10. References . . . . . . . . . . . . . . . . . . . . . . . . . 20 10. References . . . . . . . . . . . . . . . . . . . . . . . . . 20
10.1. Normative References . . . . . . . . . . . . . . . . . . 20 10.1. Normative References . . . . . . . . . . . . . . . . . . 20
10.2. Informative References . . . . . . . . . . . . . . . . . 21 10.2. Informative References . . . . . . . . . . . . . . . . . 21
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 22 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 22
1. Introduction 1. Introduction
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(LFA) [RFC5286]. This has introduced ambiguity in that if a (LFA) [RFC5286]. This has introduced ambiguity in that if a
deployment includes a mix of RSVP-TE support and SR Policy support deployment includes a mix of RSVP-TE support and SR Policy support
(for example) it is not possible to unambiguously indicate which (for example) it is not possible to unambiguously indicate which
advertisements are to be used by RSVP-TE and which advertisements are advertisements are to be used by RSVP-TE and which advertisements are
to be used by SR Policy. If the topologies are fully congruent this to be used by SR Policy. If the topologies are fully congruent this
may not be an issue, but any incongruence leads to ambiguity. may not be an issue, but any incongruence leads to ambiguity.
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
is easily extensible to the introduction of new applications and new is easily extensible to the introduction of new applications and new
use cases. use cases.
2. Requirements Discussion 2. Requirements Discussion
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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/requirements for Segment Routing (SR). [RFC7855] discusses use cases/requirements for Segment Routing (SR).
Included among these use cases is SR Policy which is defined in Included among these use cases is SR Policy which is defined in
[I-D.ietf-spring-segment-routing-policy]. If both RSVP-TE and SR [I-D.ietf-spring-segment-routing-policy]. If both RSVP-TE and SR
Policy are deployed in a network, link attribute advertisements can Policy are deployed in a network, link attribute advertisements can
be used by one or both of these applications. As there is no be used by one or both of these applications. As there is no
requirement for the link attributes advertised on a given link used requirement for the link attributes advertised on a given link used
by SR Policy to be identical to the link attributes advertised on by SR Policy to be identical to the link attributes advertised on
that same link used by RSVP-TE, there is a clear requirement to that same link used by RSVP-TE, there is a clear requirement to
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TLV 138 GMPLS-SRLG TLV 138 GMPLS-SRLG
Supports links identified by IPv4 addresses and Supports links identified by IPv4 addresses and
unnumbered links 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 code points are defined in support of Application Specific Two new code points are defined in support of Application-Specific
Link Attribute Advertisements: Link Attribute Advertisements:
1) Application Specific Link Attributes sub-TLV for TLVs 22, 23, 25, 1) Application-Specific Link Attributes sub-TLV for TLVs 22, 23, 25,
141, 222, and 223 (defined in Section 4.2 ). 141, 222, and 223 (defined in Section 4.2 ).
2)Application Specific Shared Risk Link Group (SRLG) TLV (defined in 2)Application-Specific Shared Risk Link Group (SRLG) TLV (defined in
Section 4.3). Section 4.3).
In support of these new advertisements, an application identifier bit In support of these new advertisements, an application identifier bit
mask is defined that identifies the application(s) associated with a mask is defined that identifies the application(s) associated with a
given advertisement (defined in Section 4.1). given 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. Such applications are not
subject to standardization and are outside the scope of this subject to standardization and are outside the scope of this
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The following sections define the format of these new advertisements. The following sections define the format of these new 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. A second bit mask is for non- a new IANA controlled registry. A second bit mask is for non-
standard User Defined Applications (UDAs). standard User Defined Applications (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
+--+--+--+--+--+--+--+--+ +--+--+--+--+--+--+--+--+
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MUST be ignored on receipt MUST be ignored on receipt
o Bits that are not transmitted MUST be treated as if they are set o Bits that are not transmitted MUST be treated as if they are set
to 0 on receipt. to 0 on receipt.
o Bits that are not supported by an implementation MUST be ignored o 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 22, 23, 25, 141, 222, and 223 is defined that A new sub-TLV for TLVs 22, 23, 25, 141, 222, and 223 is defined that
supports specification of the applications and application specific supports specification of the applications and application-specific
attribute values. attribute values.
Type: 16 (temporarily assigned by IANA) Type: 16 (temporarily assigned by IANA)
Length: Variable (1 octet) Length: Variable (1 octet)
Value: Value:
Application Identifier Bit Mask Application Identifier Bit Mask
(as defined in Section 4.1) (as defined in Section 4.1)
Link Attribute sub-sub-TLVs - format matches the Link Attribute sub-sub-TLVs - format matches the
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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 22, 23, 25, advertisements for the corresponding link found in TLVs 22, 23, 25,
141, 222, and 223 or TLV 138 or TLV 139 as appropriate. Link 141, 222, and 223 or TLV 138 or TLV 139 as appropriate. Link
attribute sub-sub-TLVs for the corresponding link attributes MUST NOT attribute sub-sub-TLVs for the corresponding link attributes MUST NOT
be advertised for the set of applications specified in the Standard/ be advertised for the set of applications specified in the Standard/
User Application Identifier Bit Masks and all such advertisements User Application Identifier Bit Masks and all such advertisements
MUST be ignored on receipt. MUST be ignored on receipt.
Multiple Application Specific Link Attribute sub-TLVs for the same Multiple Application-Specific Link Attribute 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 of the same link attribute for a associated with two different values of the same link attribute for a
given link. In cases where conflicting values for the same given link. In cases where conflicting values for the same
application/attribute/link are advertised all the conflicting values application/attribute/link are advertised all the conflicting values
MUST be ignored by the specified application. MUST be ignored by the specified application.
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
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the link attribute sub-sub-TLV code points. This document defines a the link attribute sub-sub-TLV code points. This document defines a
sub-sub-TLV for each of the existing sub-TLVs listed in Section 3.1 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 matches the except as noted below. The format of the sub-sub-TLVs matches the
format of the corresponding legacy sub-TLV and IANA is requested to format of the corresponding legacy sub-TLV and IANA is requested to
assign the legacy sub-TLV identifier to the corresponding sub-sub- assign 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
link. When advertised using the Application Specific Link Attributes link. When advertised using the Application-Specific Link Attributes
sub-TLV, multiple values for the same link MUST NOT be advertised. sub-TLV, multiple values for the same link MUST NOT be advertised.
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.
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length SABM and UDABM so long as the constraints discussed in length SABM and UDABM so long as the constraints discussed in
Section 4.2 and Section 6.2 are acceptable. Section 4.2 and Section 6.2 are acceptable.
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 (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 RSVP-TE bit
set, the advertisement MUST be ignored. set, 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 either by explicitly specifying the applications in the Application
Identifier Bit Mask or by using a zero length Application Identifier Identifier Bit Mask or by using a zero length Application Identifier
Bit Mask. Bit Mask.
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 new TLV is defined to advertise application-specific SRLGs for a
given link. Although similar in functionality to TLV 138 [RFC5307] given link. Although similar in functionality to TLV 138 [RFC5307]
and TLV 139 [RFC6119], a single TLV provides support for IPv4, IPv6, and TLV 139 [RFC6119], a single TLV provides support for IPv4, IPv6,
and unnumbered identifiers for a link. Unlike TLVs 138/139, it and unnumbered identifiers for a link. Unlike TLVs 138/139, 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 (Temporarily assigned by IANA) Type: 238 (Temporarily assigned by IANA)
Length: Number of octets in the value field (1 octet) Length: Number of octets in the value field (1 octet)
Value: Value:
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the SRLG values advertised in the legacy TLV MUST be used by the set the SRLG values advertised in the legacy TLV MUST be used by the set
of applications specified in the Application Identifier Bit Mask. of applications specified in the Application 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. application-specific link attributes.
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 application-specific
link attributes implies that RSVP is enabled on that link. The link attributes implies that RSVP is enabled on that link. The
absence of RSVP-TE application specific link attributes in absence of RSVP-TE application-specific link attributes in
combination with the absence of legacy advertisements implies that combination with the absence of legacy advertisements implies that
RSVP is not enabled on that link. RSVP is not enabled on that link.
In the case of SR Policy, advertisement of application specific link In the case of SR Policy, advertisement of application-specific link
attributes does not indicate enablement of SR Policy on that link. attributes does not indicate enablement of SR Policy on that link.
The advertisements are only used to support constraints that may be The advertisements are only used to support constraints that may be
applied when specifying an explicit path. SR Policy is implicitly applied when specifying an explicit path. SR Policy is implicitly
enabled on all links that are part of the Segment Routing enabled enabled on all links that are part of the Segment Routing enabled
topology independent of the existence of link attribute topology independent of the existence of link attribute
advertisements. advertisements.
In the case of LFA, advertisement of application specific link In the case of LFA, advertisement of application-specific link
attributes does not indicate enablement of LFA on that link. attributes does not indicate enablement of LFA on that link.
Enablement is controlled by local configuration. Enablement is controlled by local configuration.
If, in the future, additional standard applications are defined to If, in the future, additional standard applications are defined to
use this mechanism, the specification defining this use MUST define use this mechanism, the specification defining this use MUST define
the relationship between application specific link attribute the relationship between application-specific link attribute
advertisements and enablement for that application. advertisements and enablement for that application.
This document allows the advertisement of application specific link This document allows the advertisement of application-specific link
attributes with no application identifiers i.e., both the Standard attributes with no application identifiers i.e., both the Standard
Application Identifier Bit Mask and the User Defined Application Application Identifier Bit Mask and the User Defined Application
Identifier Bit Mask are not present (See Section 4.1). This supports Identifier Bit Mask are not present (See Section 4.1). This supports
the use of the link attribute by any application. In the presence of the use of the link attribute by any application. In the presence of
an application where the advertisement of link attribute an application where the advertisement of link attribute
advertisements is used to infer the enablement of an application on advertisements is used to infer the enablement of an application on
that link (e.g., RSVP-TE), the absence of the application identifier that link (e.g., RSVP-TE), the absence of the application identifier
leaves ambiguous whether that application is enabled on such a link. leaves ambiguous whether that application is enabled on such a link.
This needs to be considered when making use of the "any application" This needs to be considered when making use of the "any application"
encoding. encoding.
6. Deployment Considerations 6. Deployment Considerations
This section discuss deployment considerations associated with the This section discuss deployment considerations associated with the
use of application specific link attribute advertisements. use of application-specific link attribute 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 14, line 23 skipping to change at page 14, line 23
anywhere in the network anywhere in the network
o The application is SR Policy or LFA, RSVP-TE is deployed in the o The application is SR Policy or LFA, RSVP-TE is deployed in the
network, and both the set of links on which SR Policy and/or LFA network, and both the set of links on which SR Policy and/or LFA
advertisements are required and the attribute values used by SR advertisements are required and the attribute values used by SR
Policy and/or LFA on all such links is fully congruent with the Policy and/or LFA on all such links is fully congruent with the
links and attribute values used by RSVP-TE links and attribute values used by RSVP-TE
Under the conditions defined above, implementations that support the Under the conditions defined above, implementations that support the
extensions defined in this document have the choice of using legacy extensions defined in this document have the choice of using legacy
advertisements or application specific advertisements in support of advertisements or application-specific advertisements in support of
SR Policy and/or LFA. This will require implementations to provide SR Policy and/or LFA. This will require implementations to provide
controls specifying which type of advertisements are to be sent/ controls specifying which type of advertisements are to be sent/
processed on receive for these applications. Further discussion of processed on receive for these applications. Further discussion of
the associated issues can be found in Section 6.3. the associated issues can be found in Section 6.3.
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.
skipping to change at page 15, line 20 skipping to change at page 15, line 20
the use of legacy advertisements by the legacy routers. The the use of legacy advertisements by the legacy routers. The
following sub-sections discuss interoperability and backwards following sub-sections discuss interoperability and backwards
compatibility concerns for a number of deployment scenarios. compatibility concerns for a number of deployment scenarios.
6.3.1. Multiple Applications: Common Attributes with RSVP-TE 6.3.1. Multiple Applications: Common Attributes with RSVP-TE
In cases where multiple applications are utilizing a given link, one In cases where multiple applications are utilizing a given link, one
of the applications is RSVP-TE, and all link attributes for a given of the applications is RSVP-TE, and all link attributes for a given
link are common to the set of applications utilizing that link, link are common to the set of applications utilizing that link,
interoperability is achieved by using legacy advertisements and interoperability is achieved by using legacy advertisements and
sending application specific advertisements with L-flag set and no sending application-specific advertisements with L-flag set and no
link attribute values. This avoids duplication of link attribute link attribute values. This avoids duplication of link attribute
advertisements. advertisements.
6.3.2. Multiple Applications: All Attributes Not Shared with RSVP-TE 6.3.2. Multiple Applications: All Attributes Not Shared with RSVP-TE
In cases where one or more applications other than RSVP-TE are In cases where one or more applications other than RSVP-TE are
utilizing a given link and one or more link attribute values are not utilizing a given link and one or more link attribute values are not
shared with RSVP-TE, it is necessary to use application specific shared with RSVP-TE, it is necessary to use application-specific
advertisements as defined in this document. Attributes for advertisements as defined in this document. Attributes for
applications other than RSVP-TE MUST be advertised using application applications other than RSVP-TE MUST be advertised using application-
specific advertisements that have the L-flag clear. In cases where specific advertisements that have the L-flag clear. In cases where
some link attributes are shared with RSVP-TE, this requires duplicate some link attributes are shared with RSVP-TE, this requires duplicate
advertisements for those attributes. advertisements for those attributes.
These guidelines apply to cases where RSVP-TE is not using any These guidelines apply to cases where RSVP-TE is not using any
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 applications defined in this document, routers that do not For the applications defined in this document, routers that do not
support the extensions defined in this document will send and receive support the extensions defined in this document will send and receive
only legacy link attribute advertisements. So long as there is any only legacy link attribute advertisements. So long as there is any
legacy router in the network that has any of the applications legacy router in the network that has any of the applications
enabled, all routers MUST continue to advertise link attributes using enabled, all routers MUST continue to advertise link attributes using
legacy advertisements. In addition, the link attribute values legacy advertisements. In addition, the link attribute values
associated with the set of applications supported by legacy routers associated with the set of applications supported by legacy routers
(RSVP-TE, SR Policy, and/or LFA) are always shared since legacy (RSVP-TE, SR Policy, and/or LFA) are always shared since legacy
routers have no way of advertising or processing application specific routers have no way of advertising or processing application-specific
values. Once all legacy routers have been upgraded, migration from values. Once all legacy routers have been upgraded, migration from
legacy advertisements to application specific advertisements can be legacy advertisements to application-specific advertisements can be
achieved via the following steps: achieved via the following steps:
1)Send application specific advertisements while continuing to 1)Send application-specific advertisements while continuing to
advertise using legacy (all advertisements are then duplicated). advertise using legacy (all advertisements are then duplicated).
Receiving routers continue to use legacy advertisements. Receiving routers continue to use legacy advertisements.
2)Enable the use of the application specific advertisements on all 2)Enable the use of the application-specific advertisements on all
routers 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 support RSVP-TE as one of the The extensions defined in this document support RSVP-TE as one of the
supported applications. This allows that RSVP-TE could eventually supported applications. This allows that RSVP-TE could eventually
utilize the application specific advertisements. This can be done in utilize the application-specific advertisements. This can be done in
the following step-wise manner: the following step-wise 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 application specific 2)Advertise all legacy link attributes using application-specific
advertisements with L-flag clear and R-bit set. At this point both advertisements with L-flag clear and R-bit set. At this point both
legacy 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 code point changes introduced by this This section lists the protocol code point changes introduced by this
document and the related IANA changes required. document and the related IANA changes required.
For new registries defined under IS-IS TLV Codepoints Registry with For new registries defined under IS-IS TLV Codepoints Registry with
registration procedure "Expert Review", guidance for designated registration procedure "Expert Review", guidance for designated
experts can be found in [RFC7370]. experts can be found in [RFC7370].
7.1. Application Specific Link Attributes sub-TLV 7.1. Application-Specific Link Attributes sub-TLV
This document defines a new sub-TLV in the Sub-TLVs for TLVs 22, 23, This document defines a new sub-TLV in the Sub-TLVs for TLVs 22, 23,
25, 141, 222, and 223 registry. See Section 4.2 25, 141, 222, and 223 registry. See Section 4.2
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
7.2. Application Specific SRLG TLV 7.2. Application-Specific SRLG TLV
This document defines one new TLV in the IS-IS TLV Codepoints This document defines one new TLV in the IS-IS TLV Codepoints
Registry. See Section 4.3 Registry. See Section 4.3
Type Description IIH LSP SNP Purge Type Description IIH LSP SNP Purge
---- --------------------- --- --- --- ----- ---- --------------------- --- --- --- -----
238 Application Specific n y n n 238 Application-Specific n y n n
SRLG SRLG
7.3. Application Specific Link Attributes sub-sub-TLV Registry 7.3. Application-Specific Link Attributes sub-sub-TLV Registry
This document requests a new IANA registry under the IS-IS TLV This document requests a new IANA registry under the IS-IS TLV
Codepoints Registry be created to control the assignment of sub-sub- Codepoints Registry be created to control the assignment of sub-sub-
TLV codepoints for the Application Specific Link Attributes sub-TLV TLV codepoints for the Application-Specific Link Attributes sub-TLV
defined in Section 7.1. The suggested name of the new registry is defined in Section 7.1. The suggested name of the new registry is
"sub-sub-TLV code points for application specific link attributes". "sub-sub-TLV code points for application-specific link attributes".
The registration procedure is "Expert Review" as defined in The registration procedure is "Expert Review" as defined in
[RFC8126]. The following assignments are made by this document: [RFC8126]. The following assignments are made by this document:
Type Description Encoding Type Description Encoding
Reference Reference
--------------------------------------------------------- ---------------------------------------------------------
0-2 Unassigned 0-2 Unassigned
3 Administrative group (color) RFC5305 3 Administrative group (color) RFC5305
4-8 Unassigned 4-8 Unassigned
9 Maximum link bandwidth RFC5305 9 Maximum link bandwidth RFC5305
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39 Unidirectional Utilized Bandwidth RFC8570 39 Unidirectional Utilized Bandwidth RFC8570
40-255 Unassigned 40-255 Unassigned
Note to IANA: For future codepoints, in cases where the document that Note to IANA: For future codepoints, in cases where the document that
defines the encoding is different from the document that assigns the defines the encoding is different from the document that assigns the
codepoint, the encoding reference MUST be to the document that codepoint, the encoding reference MUST be to the document that
defines the encoding. defines the encoding.
Note to designated experts: If a link attribute can be advertised Note to designated experts: If a link attribute can be advertised
both as a sub-TLV of TLVs 22, 23, 25, 141, 222, and 223 and as a sub- both as a sub-TLV of TLVs 22, 23, 25, 141, 222, and 223 and as a sub-
sub-TLV of the Application Specific Link Attributes sub-TLV defined sub-TLV of the Application-Specific Link Attributes sub-TLV defined
in this document, then the same numerical code should be assigned to in this document, then the same numerical code should be assigned to
the link attribute whenever possible. the link attribute whenever possible.
7.4. Link Attribute Application Identifier Registry 7.4. Link Attribute Application Identifier Registry
This document requests a new IANA registry be created, under the This document requests a new IANA registry be created, under the
category of "Interior Gateway Protocol (IGP) Parameters", to control category of "Interior Gateway Protocol (IGP) Parameters", to control
the assignment of Application Identifier Bits. The suggested name of the assignment of Application Identifier Bits. The suggested name of
the new registry is "Link Attribute Applications". The registration the new registry is "Link Attribute Applications". The registration
policy for this registry is "Expert Review" [RFC8126]. Bit policy for this registry is "Expert Review" [RFC8126]. Bit
skipping to change at page 19, line 16 skipping to change at page 19, line 16
--------------------------------------------------------- ---------------------------------------------------------
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
7.5. SRLG sub-TLVs 7.5. SRLG sub-TLVs
This document requests a new IANA registry be created under the IS-IS This document requests a new IANA registry be created under the IS-IS
TLV Codepoints Registry to control the assignment of sub-TLV types TLV Codepoints Registry to control the assignment of sub-TLV types
for the application specific SRLG TLV. The suggested name of the new for the application-specific SRLG TLV. The suggested name of the new
registry is "Sub-TLVs for TLV 238". The registration procedure is registry is "Sub-TLVs for TLV 238". The registration procedure is
"Expert Review" as defined in [RFC8126]. The following assignments "Expert Review" as defined in [RFC8126]. The following assignments
are made by this document: are made by this document:
Value Description Encoding Value Description Encoding
Reference Reference
--------------------------------------------------------- ---------------------------------------------------------
0-3 Unassigned 0-3 Unassigned
4 Link Local/Remote Identifiers [RFC5307] 4 Link Local/Remote Identifiers [RFC5307]
5 Unassigned 5 Unassigned
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