--- 1/draft-ietf-isis-te-app-13.txt 2020-06-04 07:13:27.566465306 -0700 +++ 2/draft-ietf-isis-te-app-14.txt 2020-06-04 07:13:27.614466529 -0700 @@ -1,24 +1,24 @@ Networking Working Group L. Ginsberg Internet-Draft P. Psenak Intended status: Standards Track Cisco Systems -Expires: November 19, 2020 S. Previdi +Expires: December 5, 2020 S. Previdi Huawei W. Henderickx Nokia J. Drake Juniper Networks - May 18, 2020 + June 3, 2020 IS-IS TE Attributes per application - draft-ietf-isis-te-app-13 + draft-ietf-isis-te-app-14 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 Traffic Engineering, Loop Free Alternate) have been defined which also make use of the link attribute advertisements. In cases where multiple applications wish to make use of these link attributes the current advertisements do not support application @@ -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 November 19, 2020. + This Internet-Draft will expire on December 5, 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 @@ -70,39 +70,39 @@ Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3 2. Requirements Discussion . . . . . . . . . . . . . . . . . . . 4 3. Legacy Advertisements . . . . . . . . . . . . . . . . . . . . 4 3.1. Legacy sub-TLVs . . . . . . . . . . . . . . . . . . . . . 5 3.2. Legacy SRLG Advertisements . . . . . . . . . . . . . . . 5 4. Advertising Application Specific Link Attributes . . . . . . 6 4.1. Application Identifier Bit Mask . . . . . . . . . . . . . 6 4.2. Application Specific Link Attributes sub-TLV . . . . . . 8 - 4.2.1. Special Considerations for Maximum Link Bandwidth . . 9 + 4.2.1. Special Considerations for Maximum Link Bandwidth . . 10 4.2.2. Special Considerations for Reservable/Unreserved Bandwidth . . . . . . . . . . . . . . . . . . . . . . 10 4.2.3. Considerations for Extended TE Metrics . . . . . . . 10 - 4.3. Application Specific SRLG TLV . . . . . . . . . . . . . . 10 - 5. Attribute Advertisements and Enablement . . . . . . . . . . . 11 - 6. Deployment Considerations . . . . . . . . . . . . . . . . . . 12 - 6.1. Use of Legacy Advertisements . . . . . . . . . . . . . . 12 + 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 . . . 13 6.3. Interoperability, Backwards Compatibility and Migration Concerns . . . . . . . . . . . . . . . . . . . . . . . . 14 6.3.1. Multiple Applications: Common Attributes with RSVP- TE . . . . . . . . . . . . . . . . . . . . . . . . . 14 6.3.2. Multiple Applications: All Attributes Not Shared with RSVP-TE . . . . . . . . . . . . . . . . . . . . . . . 14 - 6.3.3. Interoperability with Legacy Routers . . . . . . . . 14 + 6.3.3. Interoperability with Legacy Routers . . . . . . . . 15 6.3.4. Use of Application Specific Advertisements for RSVP- TE . . . . . . . . . . . . . . . . . . . . . . . . . 15 - 7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 15 + 7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 16 7.1. Application Specific Link Attributes sub-TLV . . . . . . 16 7.2. Application Specific SRLG TLV . . . . . . . . . . . . . . 16 7.3. Application Specific Link Attributes sub-sub-TLV Registry 16 7.4. Link Attribute Application Identifier Registry . . . . . 17 7.5. SRLG sub-TLVs . . . . . . . . . . . . . . . . . . . . . . 18 8. Security Considerations . . . . . . . . . . . . . . . . . . . 18 9. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 19 10. References . . . . . . . . . . . . . . . . . . . . . . . . . 19 10.1. Normative References . . . . . . . . . . . . . . . . . . 19 10.2. Informative References . . . . . . . . . . . . . . . . . 20 @@ -155,22 +155,22 @@ already exists in IS-IS, it is only necessary to discuss use cases which justify the key points identified in the introduction - which are: 1. Support for indicating which applications are using the link attribute advertisements on a link 2. Support for advertising application specific values for the same attribute on a link - [RFC7855] discusses use cases/requirements for SR. Included among - these use cases is SRTE which is defined in + [RFC7855] discusses use cases/requirements for Segment Routing (SR). + Included among these use cases is SRTE which is defined in [I-D.ietf-spring-segment-routing-policy]. If both RSVP-TE and SRTE are deployed in a network, link attribute advertisements can be used by one or both of these applications. As there is no requirement for the link attributes advertised on a given link used by SRTE to be identical to the link attributes advertised on that same link used by RSVP-TE, there is a clear requirement to indicate independently which link attribute advertisements are to be used by each application. As the number of applications which may wish to utilize link attributes may grow in the future, an additional requirement is that @@ -341,27 +341,27 @@ | ... +-+-+-+-+-+-+-+-+... This field is omitted if UDABM Length is 0. NOTE: SABM/UDABM Length is arbitrarily limited to 8 octets in order to insure that sufficient space is left to advertise link attributes without overrunning the maximum length of a sub-TLV. Standard Application Identifier Bits are defined/sent starting with - Bit 0. Undefined bits MUST be transmitted as 0 and MUST be ignored - on receipt. Bits that are NOT transmitted MUST be treated as if they - are set to 0 on receipt. Bits that are not supported by an - implementation MUST be ignored on receipt. + Bit 0. Undefined bits which are transmitted MUST be transmitted as 0 + and MUST be ignored on receipt. Bits that are not transmitted MUST + be treated as if they are set to 0 on receipt. Bits that are not + supported by an implementation MUST be ignored on receipt. 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 are used starting with Bit 0 so as to minimize the number of octets required to advertise all UDAs. 4.2. Application Specific Link Attributes sub-TLV A new sub-TLV for TLVs 22, 23, 25, 141, 222, and 223 is defined which supports specification of the applications and application specific attribute values. @@ -369,42 +369,54 @@ Length: Variable (1 octet) Value: Application Identifier Bit Mask (as defined in Section 4.1) Link Attribute sub-sub-TLVs - format matches the existing formats defined in [RFC5305], [RFC7308], and [RFC8570] + If the SABM or UDABM length in the Application Identifer Bit Mask is + greater than 8, the entire sub-TLV MUST be ignored. + 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 advertisements for the corresponding link found in TLVs 22, 23, 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. + MUST be ignored by the specified application. 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 + advertised on that same link which is associated with a non-zero + length Application Identifier Bit Mask with a matching Application + Identifier Bit set. + A new registry of sub-sub-TLVs is to be created by IANA which defines 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 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 assign the legacy sub-TLV identifier to the corresponding sub-sub- TLV. 4.2.1. Special Considerations for Maximum Link Bandwidth @@ -505,31 +517,31 @@ Whether the presence of link attribute advertisements for a given application indicates that the application is enabled on that link depends upon the application. Similarly, whether the absence of link attribute advertisements indicates that the application is not enabled depends upon the application. In the case of RSVP-TE, the advertisement of application specific link attributes implies that RSVP is enabled on that link. The absence of RSVP-TE application specific link attributes in 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 SRTE, advertisement of application specific link - attributes does NOT indicate enablement of SRTE. The advertisements - are only used to support constraints which may be applied when - specifying an explicit path. SRTE is implicitly enabled on all links - which are part of the Segment Routing enabled topology independent of - the existence of link attribute advertisements + attributes does not indicate enablement of SRTE on that link. The + advertisements are only used to support constraints which may be + applied when specifying an explicit path. SRTE is implicitly enabled + on all links which are part of the Segment Routing enabled topology + independent of the existence of link attribute advertisements 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. If, in the future, additional standard applications are defined to use this mechanism, the specification defining this use MUST define the relationship between application specific link attribute advertisements and enablement for that application. This document allows the advertisement of application specific link attributes with no application identifiers i.e., both the Standard Application Identifier Bit Mask and the User Defined Application @@ -578,71 +590,67 @@ the associated issues can be found in Section 6.3. New applications which future documents define to make use of the advertisements defined in this document MUST NOT make use of legacy advertisements. This simplifies deployment of new applications by eliminating the need to support multiple ways to advertise attributes for the new applications. 6.2. Use of Zero Length Application Identifier Bit Masks - 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 - advertised on that same link which is associated with a non-zero - length Application Identifier Bit Mask with a matching Application - Identifier Bit set. If support for a new application is introduced - on any node in a network in the presence of such advertisements, - these advertisements are permitted to be used by the new application. - If this is not what is intended, then existing advertisements MUST be - readvertised with an explicit set of applications specified before a - new application is introduced. + Link attribute advertisements associated with zero length Application + Identifier Bit Masks for both standard applications and user defined + applications are usable by any application, subject to the + restrictions specified in Section 4.2. If support for a new + application is introduced on any node in a network in the presence of + such advertisements, these advertisements are permitted to be used by + the new application. If this is not what is intended, then existing + advertisements MUST be readvertised with an explicit set of + applications specified before a new application is introduced. 6.3. Interoperability, Backwards Compatibility and Migration Concerns Existing deployments of RSVP-TE, SRTE, and/or LFA utilize the legacy advertisements listed in Section 3. Routers which do not support the extensions defined in this document will only process legacy advertisements and are likely to infer that RSVP-TE is enabled on the links for which legacy advertisements exist. It is expected that deployments using the legacy advertisements will persist for a significant period of time. Therefore deployments using the - extensions defined in this document must be able to co-exist with use - of the legacy advertisements by routers which do not support the - extensions defined in this document. The following sub-sections - discuss interoperability and backwards compatibility concerns for a - number of deployment scenarios. + extensions defined in this document in the presence of routers which + do not support these extensions need to be able to interoperate with + the use of legacy advertisements by the legacy routers. The + following sub-sections discuss interoperability and backwards + compatibility concerns for a number of deployment scenarios. 6.3.1. Multiple Applications: Common Attributes with RSVP-TE In cases where multiple applications are utilizing a given link, one of the applications is RSVP-TE, and all link attributes for a given link are common to the set of applications utilizing that link, interoperability is achieved by using legacy advertisements and sending application specific advertisements with L-flag set and no link attribute values. This avoids duplication of link attribute advertisements. 6.3.2. Multiple Applications: All Attributes Not Shared with RSVP-TE 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 advertisements as defined in this document. Attributes for applications other than RSVP-TE MUST be advertised using application specific advertisements which have the L-flag clear. In cases where some link attributes are shared with RSVP-TE, this requires duplicate advertisements for those attributes. - The discussion in this section applies to cases where RSVP-TE is NOT + The discussion in this section applies to cases where RSVP-TE is not using any advertised attributes on a link and to cases where RSVP-TE is using some link attribute advertisements on the link but some link attributes cannot be shared with RSVP-TE. 6.3.3. Interoperability with Legacy Routers For the applications defined in this document, routers which 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 which has any of the applications