--- 1/draft-ietf-isis-te-app-18.txt 2020-06-29 08:13:19.993405144 -0700 +++ 2/draft-ietf-isis-te-app-19.txt 2020-06-29 08:13:20.041406367 -0700 @@ -1,24 +1,24 @@ Networking Working Group L. Ginsberg Internet-Draft P. Psenak Intended status: Standards Track Cisco Systems -Expires: December 24, 2020 S. Previdi +Expires: December 31, 2020 S. Previdi Huawei W. Henderickx Nokia J. Drake Juniper Networks - June 22, 2020 + June 29, 2020 IS-IS Application-Specific Link Attributes - draft-ietf-isis-te-app-18 + draft-ietf-isis-te-app-19 Abstract Existing traffic engineering related link attribute advertisements have been defined and are used in RSVP-TE deployments. Since the original RSVP-TE use case was defined, additional applications (e.g., Segment Routing Policy, Loop Free Alternate) that also make use of the link attribute advertisements have been defined . In cases where multiple applications wish to make use of these link attributes, the current advertisements do not support application-specific values for @@ -43,21 +43,21 @@ 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 and may be updated, replaced, or obsoleted by other documents at any time. It is inappropriate to use Internet-Drafts as reference 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 (c) 2020 IETF Trust and the persons identified as the document authors. All rights reserved. This document is subject to BCP 78 and the IETF Trust's Legal Provisions Relating to IETF Documents (https://trustee.ietf.org/license-info) in effect on the date of publication of this document. Please review these documents @@ -67,42 +67,42 @@ the Trust Legal Provisions and are provided without warranty as described in the Simplified BSD License. Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3 2. Requirements Discussion . . . . . . . . . . . . . . . . . . . 4 3. Legacy Advertisements . . . . . . . . . . . . . . . . . . . . 5 3.1. Legacy sub-TLVs . . . . . . . . . . . . . . . . . . . . . 5 3.2. Legacy SRLG Advertisements . . . . . . . . . . . . . . . 6 - 4. Advertising Application-Specific Link Attributes . . . . . . 6 - 4.1. Application Identifier Bit Mask . . . . . . . . . . . . . 6 + 4. Advertising Application-Specific Link Attributes . . . . . . 7 + 4.1. Application Identifier Bit Mask . . . . . . . . . . . . . 7 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 - Bandwidth . . . . . . . . . . . . . . . . . . . . . . 10 + Bandwidth . . . . . . . . . . . . . . . . . . . . . . 11 4.2.3. Considerations for Extended TE Metrics . . . . . . . 11 - 4.3. Application-Specific SRLG TLV . . . . . . . . . . . . . . 11 - 5. Attribute Advertisements and Enablement . . . . . . . . . . . 12 - 6. Deployment Considerations . . . . . . . . . . . . . . . . . . 13 - 6.1. Use of Legacy Advertisements . . . . . . . . . . . . . . 13 - 6.2. Use of Zero Length Application Identifier Bit Masks . . . 14 + 4.3. Application-Specific SRLG TLV . . . . . . . . . . . . . . 12 + 5. Attribute Advertisements and Enablement . . . . . . . . . . . 13 + 6. Deployment Considerations . . . . . . . . . . . . . . . . . . 14 + 6.1. Use of Legacy Advertisements . . . . . . . . . . . . . . 14 + 6.2. Use of Zero Length Application Identifier Bit Masks . . . 15 6.3. Interoperability, Backwards Compatibility and Migration - Concerns . . . . . . . . . . . . . . . . . . . . . . . . 14 + Concerns . . . . . . . . . . . . . . . . . . . . . . . . 15 6.3.1. Multiple Applications: Common Attributes with RSVP- TE . . . . . . . . . . . . . . . . . . . . . . . . . 15 6.3.2. Multiple Applications: All Attributes Not Shared with 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- TE . . . . . . . . . . . . . . . . . . . . . . . . . 16 - 7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 16 + 7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 17 7.1. Application-Specific Link Attributes sub-TLV . . . . . . 17 7.2. Application-Specific SRLG TLV . . . . . . . . . . . . . . 17 7.3. Application-Specific Link Attributes sub-sub-TLV Registry 17 7.4. Link Attribute Application Identifier Registry . . . . . 18 7.5. SRLG sub-TLVs . . . . . . . . . . . . . . . . . . . . . . 19 8. Security Considerations . . . . . . . . . . . . . . . . . . . 19 9. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 20 10. References . . . . . . . . . . . . . . . . . . . . . . . . . 20 10.1. Normative References . . . . . . . . . . . . . . . . . . 20 10.2. Informative References . . . . . . . . . . . . . . . . . 21 @@ -127,20 +127,30 @@ link attributes historically used by RSVP-TE have been introduced. Such applications include Segment Routing Policy (SR Policy) [I-D.ietf-spring-segment-routing-policy] and Loop Free Alternates (LFA) [RFC5286]. This has introduced ambiguity in that if a deployment includes a mix of RSVP-TE support and SR Policy support (for example) it is not possible to unambiguously indicate which 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 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 supported on a link but the link attribute values associated with each application differ. Current advertisements do not support advertising application-specific values for the same attribute on a specific link. This document defines extensions that address these issues. Also, as evolution of use cases for link attributes can be expected to continue in the years to come, this document defines a solution that is easily extensible to the introduction of new applications and new @@ -237,24 +246,24 @@ TLV 139 IPv6 SRLG Supports links identified by IPv6 addresses Note that [RFC6119] prohibits the use of TLV 139 when it is possible to use TLV 138. 4. Advertising Application-Specific Link Attributes 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, - 141, 222, and 223 (defined in Section 4.2 ). + 1) ASLA sub-TLV for TLVs 22, 23, 25, 141, 222, and 223 (defined in + Section 4.2 ). 2)Application-Specific Shared Risk Link Group (SRLG) TLV (defined in Section 4.3). In support of these new advertisements, an application identifier bit mask is defined that identifies the application(s) associated with a given advertisement (defined in Section 4.1). In addition to supporting the advertisement of link attributes used by standardized applications, link attributes can also be advertised @@ -402,24 +410,25 @@ 141, 222, and 223 or TLV 138 or TLV 139 as appropriate. Link attribute sub-sub-TLVs for the corresponding link attributes MUST NOT be advertised for the set of applications specified in the Standard/ User Application Identifier Bit Masks and all such advertisements MUST be ignored on receipt. Multiple Application-Specific Link Attribute sub-TLVs for the same link MAY be advertised. When multiple sub-TLVs for the same link are advertised, they SHOULD advertise non-conflicting application/ attribute pairs. A conflict exists when the same application is - associated with two different values of the same link attribute for a - given link. In cases where conflicting values for the same - application/attribute/link are advertised all the conflicting values - MUST be ignored by the specified application. + associated with two different values for the same link attribute for + a given link. In cases where conflicting values for the same + application/attribute/link are advertised the first advertisement + 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 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. If link attributes are advertised associated with zero length Application Identifier Bit Masks for both standard applications and user defined applications, then any Standard Application and/or any User Defined Application is permitted to use that set of link attributes so long as there is not another set of attributes @@ -676,29 +685,28 @@ For the applications defined in this document, routers that do not support the extensions defined in this document will send and receive only legacy link attribute advertisements. So long as there is any legacy router in the network that has any of the applications enabled, all routers MUST continue to advertise link attributes using legacy advertisements. In addition, the link attribute values associated with the set of applications supported by legacy routers (RSVP-TE, SR Policy, and/or LFA) are always shared since legacy routers have no way of advertising or processing application-specific values. Once all legacy routers have been upgraded, migration from - legacy advertisements to application-specific advertisements can be - achieved via the following steps: + legacy advertisements to ASLA advertisements can be achieved via the + following steps: - 1)Send application-specific advertisements while continuing to - advertise using legacy (all advertisements are then duplicated). - Receiving routers continue to use legacy advertisements. + 1)Send ASLA advertisements while continuing to advertise using legacy + (all advertisements are then duplicated). Receiving routers continue + to use legacy advertisements. - 2)Enable the use of the application-specific advertisements on all - routers + 2)Enable the use of the ASLA advertisements on all routers 3)Remove legacy advertisements When the migration is complete, it then becomes possible to advertise incongruent values per application on a given link. 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- specific advertisements defined in this document MUST discuss @@ -706,24 +714,23 @@ in the presence of routers that do not support the new application. 6.3.4. Use of Application-Specific Advertisements for RSVP-TE The extensions defined in this document support RSVP-TE as one of the supported applications. This allows that RSVP-TE could eventually utilize the application-specific advertisements. This can be done in the following step-wise manner: 1)Upgrade all routers to support the extensions in this document - - 2)Advertise all legacy link attributes using application-specific - advertisements with L-flag clear and R-bit set. At this point both - legacy and application-specific advertisements are being sent. + 2)Advertise all legacy link attributes using ASLA advertisements with + L-flag clear and R-bit set. At this point both legacy and + application-specific advertisements are being sent. 3)Remove legacy advertisements 7. IANA Considerations This section lists the protocol code point changes introduced by this document and the related IANA changes required. For new registries defined under IS-IS TLV Codepoints Registry with registration procedure "Expert Review", guidance for designated