--- 1/draft-ietf-isis-te-app-07.txt 2019-10-17 08:13:06.012253955 -0700 +++ 2/draft-ietf-isis-te-app-08.txt 2019-10-17 08:13:06.048254872 -0700 @@ -1,24 +1,24 @@ Networking Working Group L. Ginsberg Internet-Draft P. Psenak Intended status: Standards Track Cisco Systems -Expires: April 6, 2020 S. Previdi +Expires: April 19, 2020 S. Previdi Huawei W. Henderickx Nokia J. Drake Juniper Networks - October 4, 2019 + October 17, 2019 IS-IS TE Attributes per application - draft-ietf-isis-te-app-07 + draft-ietf-isis-te-app-08 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., SRTE, LFA) 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 specific values for a given attribute nor do @@ -47,21 +47,21 @@ 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 April 6, 2020. + This Internet-Draft will expire on April 19, 2020. Copyright Notice Copyright (c) 2019 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 @@ -78,35 +78,37 @@ 3. Legacy Advertisements . . . . . . . . . . . . . . . . . . . . 4 3.1. Legacy sub-TLVs . . . . . . . . . . . . . . . . . . . . . 4 3.2. Legacy SRLG Advertisements . . . . . . . . . . . . . . . 5 4. Advertising Application Specific Link Attributes . . . . . . 5 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 4.2.2. Special Considerations for Unreserved Bandwidth . . . 9 4.3. Application Specific SRLG TLV . . . . . . . . . . . . . . 9 5. Deployment Considerations . . . . . . . . . . . . . . . . . . 10 - 6. Attribute Advertisements and Enablement . . . . . . . . . . . 11 + 5.1. Use of Legacy Advertisements . . . . . . . . . . . . . . 11 + 5.2. Use of Zero Length Application Identifier Bit Masks . . . 11 + 6. Attribute Advertisements and Enablement . . . . . . . . . . . 12 7. Interoperability, Backwards Compatibility and Migration - Concerns . . . . . . . . . . . . . . . . . . . . . . . . . . 12 - 7.1. RSVP-TE only deployments . . . . . . . . . . . . . . . . 12 - 7.2. Multiple Applications: Common Attributes with RSVP-TE . 12 - 7.3. Multiple Applications: All Attributes Not Shared w RSVP- - TE . . . . . . . . . . . . . . . . . . . . . . . . . . . 12 - 7.4. Use of Application Specific Advertisements for RSVP-TE . 13 - 8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 13 - 9. Security Considerations . . . . . . . . . . . . . . . . . . . 15 - 10. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 15 - 11. References . . . . . . . . . . . . . . . . . . . . . . . . . 15 - 11.1. Normative References . . . . . . . . . . . . . . . . . . 15 - 11.2. Informative References . . . . . . . . . . . . . . . . . 16 - Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 16 + Concerns . . . . . . . . . . . . . . . . . . . . . . . . . . 13 + 7.1. Multiple Applications: Common Attributes with RSVP-TE . 13 + 7.2. Multiple Applications: All Attributes Not Shared w RSVP- + TE . . . . . . . . . . . . . . . . . . . . . . . . . . . 13 + 7.3. Use of Application Specific Advertisements for RSVP-TE . 14 + + 8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 14 + 9. Security Considerations . . . . . . . . . . . . . . . . . . . 16 + 10. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 16 + 11. References . . . . . . . . . . . . . . . . . . . . . . . . . 16 + 11.1. Normative References . . . . . . . . . . . . . . . . . . 16 + 11.2. Informative References . . . . . . . . . . . . . . . . . 17 + Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 17 1. Introduction Advertisement of link attributes by the Intermediate-System-to- Intermediate-System (IS-IS) protocol in support of traffic engineering (TE) was introduced by [RFC5305] and extended by [RFC5307], [RFC6119], and [RFC8570]. Use of these extensions has been associated with deployments supporting Traffic Engineering over Multiprotocol Label Switching (MPLS) in the presence of Resource Reservation Protocol (RSVP) - more succinctly referred to as RSVP-TE. @@ -230,96 +232,96 @@ Identification of the set of applications associated with link attribute advertisements utilizes two bit masks. One bit mask is for standard applications where the definition of each bit is defined in a new IANA controlled registry. A second bit mask is for non- standard User Defined Applications(UDAs). The encoding defined below is used by both the Application Specific Link Attributes sub-TLV and the Application Specific SRLG TLV. 0 1 2 3 4 5 6 7 - +-+-+-+-+-+-+-+-+ - | SABML+F | 1 octet - +-+-+-+-+-+-+-+-+ - | UDABML+F | 1 octet - +-+-+-+-+-+-+-+-+ + +--+--+--+--+--+--+--+--+ + | SABM Length + Flag | 1 octet + +--+--+--+--+--+--+--+--+ + | UDABM Length + Flag | 1 octet + +--+--+--+--+--+--+--+--+ | SABM ... 0 - 127 octets - +-+-+-+-+-+-+-+-+ + +--+--+--+--+--+--+--+--+ | UDABM ... 0 - 127 octets - +-+-+-+-+-+-+-+-+ + +--+--+--+--+--+--+--+--+ - SABML+F (1 octet) + SABM Length + Flag (1 octet) Standard Application Identifier Bit Mask - Length/Flags + Length + Flag 0 1 2 3 4 5 6 7 +-+-+-+-+-+-+-+-+ - |L| SA-Length | + |L| SABM Length | +-+-+-+-+-+-+-+-+ L-flag: When set, applications listed (both Standard and User Defined) 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. - SA-Length: Indicates the length in octets (0-127) of the Bit Mask - for Standard Applications. + SABM Length: Indicates the length in octets (0-127) of the + Bit Mask for Standard Applications. - UDABML+F (1 octet) + UDABM Length + Flag (1 octet) User Defined Application Identifier Bit Mask - Length/Flags + Length + Flag 0 1 2 3 4 5 6 7 +-+-+-+-+-+-+-+-+ - |R| UDA-Length | + |R| UDABM Length| +-+-+-+-+-+-+-+-+ R: Reserved. SHOULD be transmitted as 0 and MUST be ignored on receipt - UDA-Length: Indicates the length in octets (0-127) of the Bit Mask - for User Defined Applications. + UDABM Length: Indicates the length in octets (0-127) of the + Bit Mask for User Defined Applications. SABM (variable length) Standard Application Identifier Bit Mask - (SA-Length * 8) bits + (SABM Length * 8) bits - This is omitted if SA-Length is 0. + This is omitted if SABM Length is 0. 0 1 2 3 4 5 6 7 ... +-+-+-+-+-+-+-+-+... |R|S|F| ... +-+-+-+-+-+-+-+-+... R-bit: Set to specify RSVP-TE S-bit: Set to specify Segment Routing - Traffic Engineering + Traffic Engineering (SRTE) - F-bit: Set to specify Loop Free Alternate + F-bit: Set to specify Loop Free Alternate (LFA) (includes all LFA types) UDABM (variable length) User Defined Application Identifier Bit Mask - (UDA-Length * 8) bits + (UDABM Length * 8) bits 0 1 2 3 4 5 6 7 ... +-+-+-+-+-+-+-+-+... | ... +-+-+-+-+-+-+-+-+... - This is omitted if UDA-Length is 0. + This is omitted if UDABM Length is 0. - NOTE: If both SA-length and UDA-Length are zero, then the + NOTE: If both SABM Length and UDABM Length are zero, then the attributes associated with this Attribute Identifier Bit Mask MAY be used by any Standard Application and any User Defined Application. Standard Application Identifier Bits are defined/sent starting with Bit 0. Additional bit definitions that may be defined in the future SHOULD be assigned in ascending bit order so as to minimize the number of octets that will need to be transmitted. 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 @@ -446,20 +448,59 @@ the corresponding legacy TLV (see Section 3.2) can be identified and the SRLG values advertised in the legacy TLV MUST be used by the set of applications specified in the Application Identifier Bit Mask. 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 violated, the L-flag MUST be considered set for this application. 5. Deployment Considerations + This section discuss deployment considerations associated with the + use of application specific link attribute advertisements. + +5.1. Use of Legacy Advertisements + + Bit Identifers for Standard Applications are defined in Section 4.1. + All of the identifiers defined in this document are associated with + applications which were already deployed in some networks prior to + the writing of this document. Therefore, such applications have been + deployed using the legacy advertisements. The Standard Applications + defined in this document MAY continue to use legacy advertisements + for a given link so long as at least one of the following conditions + is true: + + o The application is RSVP-TE + + o The application is SRTE or LFA and RSVP-TE is not deployed + anywhere in the network + + o The application is SRTE or LFA, RSVP-TE is deployed in the + network, and both the set of links on which SRTE and/or LFA + advertisements are required and the attribute values used by SRTE + and/or LFA on all such links is fully congruent with the links and + attribute values used by RSVP-TE + + Under the conditions defined above, implementations which support the + extensions defined in this document have the choice of using legacy + advertisements or application specific advertisements in support of + SRTE and/or LFA. This will require implementations to provide + controls specifying which type of advertisements are to be sent/ + processed on receive for these applications. Further discussion of + the associated issues can be found in Section 7. + + New applications which future documents define to make use of the + advertisements defined in this document MUST NOT make use of legacy + advertisements. + +5.2. 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 that set of link attributes MAY be used by any application. If support for a new application is introduced on any node in a network in the presence of such advertisements, these advertisements MAY 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. @@ -468,21 +509,24 @@ This document defines extensions to support the advertisement of application specific link attributes. 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. + 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. 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 In the case of LFA, advertisement of application specific link attributes does NOT indicate enablement of LFA on that link. @@ -500,69 +544,63 @@ the use of the link attribute by any application. In the presence of an application where the advertisement of link attribute advertisements is used to infer the enablement of an application on that link (e.g., RSVP-TE), the absence of the application identifier leaves ambiguous whether that application is enabled on such a link. This needs to be considered when making use of the "any application" encoding. 7. Interoperability, Backwards Compatibility and Migration Concerns - Existing deployments of RSVP-TE 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. + 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. Note that in all cases the defined strategy can be employed on a per link basis. -7.1. RSVP-TE only deployments - - In deployments where RSVP-TE is the only application utilizing link - attribute advertisements, use of the the legacy advertisements can - continue without change. - -7.2. Multiple Applications: Common Attributes with RSVP-TE +7.1. 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-bit set and no link attribute values. This avoids duplication of link attribute advertisements. -7.3. Multiple Applications: All Attributes Not Shared w RSVP-TE +7.2. Multiple Applications: All Attributes Not Shared w 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 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-bit 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 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. -7.4. Use of Application Specific Advertisements for RSVP-TE +7.3. 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 extensions in this document 2)Readvertise all legacy link attributes using application specific advertisements with L-bit clear and R-bit set.