draft-ietf-isis-te-app-18.txt   draft-ietf-isis-te-app-19.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 24, 2020 S. Previdi Expires: December 31, 2020 S. Previdi
Huawei Huawei
W. Henderickx W. Henderickx
Nokia Nokia
J. Drake J. Drake
Juniper Networks Juniper Networks
June 22, 2020 June 29, 2020
IS-IS Application-Specific Link Attributes IS-IS Application-Specific Link Attributes
draft-ietf-isis-te-app-18 draft-ietf-isis-te-app-19
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
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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
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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 24, 2020. This Internet-Draft will expire on December 31, 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 . . . . . . 7
4.1. Application Identifier Bit Mask . . . . . . . . . . . . . 6 4.1. Application Identifier Bit Mask . . . . . . . . . . . . . 7
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 . . 11
4.2.2. Special Considerations for Reservable/Unreserved 4.2.2. Special Considerations for Reservable/Unreserved
Bandwidth . . . . . . . . . . . . . . . . . . . . . . 10 Bandwidth . . . . . . . . . . . . . . . . . . . . . . 11
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 . . . . . . . . . . . . . . 12
5. Attribute Advertisements and Enablement . . . . . . . . . . . 12 5. Attribute Advertisements and Enablement . . . . . . . . . . . 13
6. Deployment Considerations . . . . . . . . . . . . . . . . . . 13 6. Deployment Considerations . . . . . . . . . . . . . . . . . . 14
6.1. Use of Legacy Advertisements . . . . . . . . . . . . . . 13 6.1. Use of Legacy Advertisements . . . . . . . . . . . . . . 14
6.2. Use of Zero Length Application Identifier Bit Masks . . . 14 6.2. Use of Zero Length Application Identifier Bit Masks . . . 15
6.3. Interoperability, Backwards Compatibility and Migration 6.3. Interoperability, Backwards Compatibility and Migration
Concerns . . . . . . . . . . . . . . . . . . . . . . . . 14 Concerns . . . . . . . . . . . . . . . . . . . . . . . . 15
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 . . . . . . . . 16
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 . . . . . . . . . . . . . . . . . . . . . 17
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
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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 Policy (SR Policy) Such applications include Segment Routing Policy (SR Policy)
[I-D.ietf-spring-segment-routing-policy] and Loop Free Alternates [I-D.ietf-spring-segment-routing-policy] and Loop Free Alternates
(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 example where this ambiguity causes a problem is a network 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. 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
advertised for that link, it assumes RSVP-TE is enabled on that link,
even though it is not. If such RSVP-TE head-end router tries to
setup an RSVP-TE path via that link, it will result in a path setup
failure.
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
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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 (ASLA) Advertisements:
1) Application-Specific Link Attributes sub-TLV for TLVs 22, 23, 25, 1) ASLA sub-TLV for TLVs 22, 23, 25, 141, 222, and 223 (defined in
141, 222, and 223 (defined in Section 4.2 ). 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
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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 for the same link attribute for
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 all the conflicting values application/attribute/link are advertised the first advertisement
MUST be ignored by the specified application. received in the lowest numbered LSP SHOULD be used and subsequent
advertisements of the same attribute SHOULD 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.
If link attributes are advertised associated with zero length If link attributes are 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, then any Standard Application and/or any user defined applications, then any Standard Application and/or any
User Defined Application is permitted to use that set of link User Defined Application is permitted to use that set of link
attributes so long as there is not another set of attributes attributes so long as there is not another set of attributes
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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 ASLA advertisements can be achieved via the
achieved via the following steps: following steps:
1)Send application-specific advertisements while continuing to 1)Send ASLA advertisements while continuing to advertise using legacy
advertise using legacy (all advertisements are then duplicated). (all advertisements are then duplicated). Receiving routers continue
Receiving routers continue to use legacy advertisements. to use legacy advertisements.
2)Enable the use of the application-specific advertisements on all 2)Enable the use of the ASLA 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
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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 ASLA advertisements with
2)Advertise all legacy link attributes using application-specific L-flag clear and R-bit set. At this point both legacy and
advertisements with L-flag clear and R-bit set. At this point both 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
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