Networking Working Group L. Ginsberg Internet-Draft P. Psenak Intended status: Standards Track S. Previdi Expires: December 2, 2017 Cisco Systems W. Henderickx Nokia May 31, 2017 IS-IS TE Attributes per application draft-ginsberg-isis-te-app-01.txt Abstract Existing traffic engineering related link attribute advertisements have been defined and are used in RSVP-TE deployments. 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 they support indication of which applications are using the advertised value for a given link. This draft introduces new link attribute advertisements which address both of these shortcomings. It also discusses backwards compatibility issues and how to minimize duplicate advertisements in the presence of routers which do not support the extensions defined in this document. Requirements Language The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in RFC 2119 [RFC2119]. Status of This Memo This Internet-Draft is submitted in full conformance with the provisions of BCP 78 and BCP 79. 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 http://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." Ginsberg, et al. Expires December 2, 2017 [Page 1] Internet-Draft draft-ginsberg-isis-te-app May 2017 This Internet-Draft will expire on December 2, 2017. Copyright Notice Copyright (c) 2017 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 (http://trustee.ietf.org/license-info) in effect on the date of publication of this document. Please review these documents carefully, as they describe your rights and restrictions with respect to this document. Code Components extracted from this document must include Simplified BSD License text as described in Section 4.e of the Trust Legal Provisions and are provided without warranty as described in the Simplified BSD License. Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 2. Requirements Discussion . . . . . . . . . . . . . . . . . . . 3 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 Bit Mask . . . . . . . . . . . . . . . . . . 6 4.2. Application Specific Link Attributes sub-TLV . . . . . . 7 4.3. Application Specific SRLG TLV . . . . . . . . . . . . . . 8 5. Interoperability, Backwards Compatibility and Migration Concerns . . . . . . . . . . . . . . . . . . . . . . . . . . 9 5.1. RSVP-TE only deployments . . . . . . . . . . . . . . . . 9 5.2. Multiple Applications: Common Attributes with RSVP-TE . 9 5.3. Multiple Applications: All Attributes Not Shared w RSVP- TE . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 5.4. Deprecating legacy advertisements . . . . . . . . . . . . 10 6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 10 7. Security Considerations . . . . . . . . . . . . . . . . . . . 12 8. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 12 9. References . . . . . . . . . . . . . . . . . . . . . . . . . 12 9.1. Normative References . . . . . . . . . . . . . . . . . . 12 9.2. Informative References . . . . . . . . . . . . . . . . . 13 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 13 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 Ginsberg, et al. Expires December 2, 2017 [Page 2] Internet-Draft draft-ginsberg-isis-te-app May 2017 [RFC5307], [RFC6119], and [RFC7810]. 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. Although implementations vary in their exact interpretation, it is fair to say that the presence of any of the link attribute advertisements currently defined (excluding link identifier advertisements) are used by many implementations to imply the use of that link by RSVP-TE. In recent years new applications have been introduced which have use cases for many of the link attributes historically used by RSVP-TE. Such applications include Segment Routing Traffic Engineering (SR-TE) and Loop Free Alternates (LFA). This has introduced ambiguity in that if a deployment includes a mix of RSVP-TE support and SR-TE support (for example) it is not possible to unambiguously indicate which advertisements indicate support for/use by RSVP-TE and which advertisements indicate support for/use by SR-TE. If the topologies are fully congruent this may not be an issue, but any incongruence leads to ambiguity. 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 which 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 which is easily extensible to the introduction of new applications and new use cases. 2. Requirements Discussion As stated previously, evolution of use cases for link attributes can be expected to continue - so any discussion of existing use cases is limited to requirements which are known at the time of this writing. However, in order to determine the functionality required beyond what 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 Ginsberg, et al. Expires December 2, 2017 [Page 3] Internet-Draft draft-ginsberg-isis-te-app May 2017 [RFC7855] discusses use cases/requirements for SR. Included among these use cases is SR-TE. If both RSVP-TE and SR-TE are deployed in a network, links can be used by one or both of these applications. As there is no requirement for the topology supported for SR-TE to be congruent to the topology supported for RSVP-TE, there is a clear requirement to indicate independently which applications are associated with a given link. If both RSVP-TE and SR-TE are enabled on a given link, it is also possible that an attribute value such as Maximum Bandwidth to be utilized by SR-TE may be different than/disjoint from the Maximum Bandwidth to be utilized by RSVP-TE. This leads to the requirement that the solution support the advertisement of unique values for a given link/attribute/application. As the number of applications which may wish to utilize link attributes may grow in the future, an additional requirement is that the extensions defined allow the association of additional applications to link attributes without altering the format of the advertisements or introducing new backwards compatibility issues. Finally, there may still be many cases where a single attribute value can be shared among multiple applications, so the solution must minimize advertising duplicate link/attribute pairs whenever possible. 3. Legacy Advertisements There are existing advertisements used in support of RSVP-TE. These advertisements include sub-TLVs for TLVs 22, 23, 141, 222, and 223 and TLVs for SRLG advertisement. 3.1. Legacy sub-TLVs Ginsberg, et al. Expires December 2, 2017 [Page 4] Internet-Draft draft-ginsberg-isis-te-app May 2017 Sub-TLVs for TLVs 22, 23, 141, 222, and 223 Code Point/Attribute Name -------------------------- 3 Administrative group (color) 9 Maximum link bandwidth 10 Maximum reservable link bandwidth 11 Unreserved bandwidth 14 Extended Administrative Group 33 Unidirectional Link Delay 34 Min/Max Unidirectional Link Delay 35 Unidirectional Delay Variation 36 Unidirectional Link Loss 37 Unidirectional Residual Bandwidth 38 Unidirectional Available Bandwidth 39 Unidirectional Utilized Bandwidth 3.2. Legacy SRLG Advertisements TLV 138 GMPLS-SRLG Supports links identified by IPv4 addresses and unnumbered links 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: 1) Application Specific Link Attributes sub-TLV for TLVs 22, 23, 141, 222, and 223 2)Application Specific Shared Risk Link Group (SRLG) TLV In support of these new advertisements, an application bit mask is defined which identifies the application(s) associated with a given advertisement. The following sections define the format of these new advertisements. Ginsberg, et al. Expires December 2, 2017 [Page 5] Internet-Draft draft-ginsberg-isis-te-app May 2017 4.1. Application Bit Mask Identification of the set of applications associated with the link attribute advertisements utilizes a bit mask where the definition of each bit is defined in a new IANA controlled registry. This encoding is used by both the Application Specific Link Attributes sub-TLV and the Application Specific SRLG TLV. Bit Mask Length: Non-zero (1 octet) Application Bit Mask: Size is (Bit Mask Length+7)/8 The following bits are assigned/reserved: 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |L|R|S|F| | UDA Use | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ L-bit: Applications listed MUST use the legacy advertisements for the corresponding link found in TLVs 22, 23, 141, 222, and 223 or TLV 138 or TLV 139 as appropriate. R-bit: RSVP-TE S-bit: Segment Routing Traffic Engineering F-bit: Loop Free Alternate UDA Use: These bits are reserved for User Defined Application (UDA) use. These bits MUST NOT be assigned by IANA for any standards based use. 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 bits 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 receipt. The second octet is reserved for local use by proprietary and/or experimental applications. These bits MUST NOT be assigned by IANA for any standards based use. IANA owns the assignment of bits 0 - 7 and bits 16 and greater. Note that the octet associated with UDA Use need only be transmitted if any of the following conditions is met: Ginsberg, et al. Expires December 2, 2017 [Page 6] Internet-Draft draft-ginsberg-isis-te-app May 2017 o One of the UDA bits is set o Bit 16 or greater is set 4.2. Application Specific Link Attributes sub-TLV A new sub-TLV for TLVs 22, 23, 141, 222, and 223 is defined which supports specification of the applications and application specific attribute values. Type: 15 (suggested value - to be assigned by IANA) Length: Variable (1 octet) Value: Application Bit Mask (as defined in Section 3.1) Link Attribute sub-sub-TLVs - format matches the existing formats defined in [RFC5305] and [RFC7810] When the L-bit is set in the Application Bit Mask, all of the applications specified in the bit mask MUST use the link attribute sub-TLV advertisements listed in Section 3.1 for the corresponding link. Application specific link attribute sub-sub-TLVs for the corresponding link attributes MUST NOT be advertised for the set of applications specified in the Application Bit Mask and all such advertisements MUST be ignored on receipt. Multiple 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. In cases where there are multiple sub-TLVs for the same link and there is a conflict in the attribute information advertised the behavior of the receiver is undefined. For a given application, the setting of the L-bit MUST be the same in all sub-TLVs for a given link. In cases where this constraint is violated, the L-bit MUST be considered set for this application. A new registry of sub-sub-TLVs is to be created by IANA which defines the link attribute sub-sub-TLV code points. A sub-sub-TLV is defined for each of the existing sub-TLVs listed in Section 3.1. 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 identifer to the corresponding sub-sub-TLV. Ginsberg, et al. Expires December 2, 2017 [Page 7] Internet-Draft draft-ginsberg-isis-te-app May 2017 4.3. Application Specific SRLG TLV A new TLV is defined to advertise application specific SRLGs for a given link. Although similar in functionality to TLV 138 (defined by [RFC5307]) and TLV 139 (defined by [RFC6119], a single TLV provides support for IPv4, IPv6, and unnumbered identifiers for a link. Unlike TLVs 138/139, it utilizes sub-TLVs to encode the link identifiers in order to provide the flexible formatting required to support multiple link identifier types. Type: 238 (Suggested value - to be assigned by IANA) Length: Number of octets in the value field (1 octet) Value: Neighbor System-ID + pseudo-node ID (7 octets) Application Bit Mask (as defined in Section 3.1) Length of sub-TLVs (1 octet) Link Identifier sub-TLVs (variable) 0 or more SRLG Values (Each value is 4 octets) The following Link Identifier sub-TLVs are defined. The type values are suggested and will be assigned by IANA - but as the formats are identical to existing sub-TLVs defined for TLVs 22, 23, 141, 222, and 223 the use of the suggested sub-TLV types is strongly encouraged. Type Description 4 Link Local/Remote Identifiers (see [RFC5307]) 6 IPv4 interface address (see [RFC5305]) 8 IPv4 neighbor address (see [RFC5305]) 12 IPv6 Interface Address (see [RFC6119]) 13 IPv6 Neighbor Address (see [RFC6119]) At least one set of link identifiers (IPv4, IPv6, or unnumbered) MUST be present. TLVs which do not meet this requirement MUST be ignored. Multiple TLVs for the same link MAY be advertised. When the L-bit is set in the Application Bit Mask, SRLG values MUST NOT be included in the TLV. Any SRLG values which are advertised MUST be ignored. Based on the link identifiers advertised 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 Bit Mask. For a given application, the setting of the L-bit MUST be the same in all TLVs for a given link. In cases where this constraint is violated, the L-bit MUST be considered set for this application. Ginsberg, et al. Expires December 2, 2017 [Page 8] Internet-Draft draft-ginsberg-isis-te-app May 2017 5. 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. Note that in all cases the defined strategy can be employed on a per link basis. 5.1. 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. 5.2. 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. 5.3. 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 enabled on a link and to cases where RSVP-TE is enabled on the link but some link attributes cannot be shared with RSVP-TE. Ginsberg, et al. Expires December 2, 2017 [Page 9] Internet-Draft draft-ginsberg-isis-te-app May 2017 5.4. Deprecating legacy advertisements The extensions defined in this document support RSVP-TE as one of the supported applications - so a long term goal for deployments would be to deprecate use of the legacy advertisements in support of RSVP-TE. 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. 3)Remove legacy advertisements 6. IANA Considerations This document defines a new sub-TLV for TLVs 22, 23, 141, 222, and 223. Type Description 22 23 141 222 223 ---- --------------------- --- --- --- --- --- 15 Application Specific y y y y y Link Attributes This document defines one new TLV: Type Description IIH SNP LSP Purge ---- --------------------- --- --- --- ----- 238 Application Specific n n y n SRLG This document requests a new IANA registry be created to control the assignment of sub-sub-TLV codepoints for the Application Specific Link Attributes sub-TLV. The suggested name of the new registry is "sub-sub-TLV code points for application link attributes". The registration procedure is "Expert Review" as defined in [RFC5226]. The following assignments are made by this document: Ginsberg, et al. Expires December 2, 2017 [Page 10] Internet-Draft draft-ginsberg-isis-te-app May 2017 Type Description --------------------------------------------------------- 3 Administrative group (color) 9 Maximum link bandwidth 10 Maximum reservable link bandwidth 11 Unreserved bandwidth 14 Extended Administrative Group 33 Unidirectional Link Delay 34 Min/Max Unidirectional Link Delay 35 Unidirectional Delay Variation 36 Unidirectional Link Loss 37 Unidirectional Residual Bandwidth 38 Unidirectional Available Bandwidth 39 Unidirectional Utilized Bandwidth This document requests a new IANA registry be created to control the assignment of application bit identifiers. The suggested name of the new registry is "Link Attribute Applications". The registration procedure is "Expert Review" as defined in [RFC5226]. The following assignments are made by this document: Bit # Name --------------------------------------------------------- 0 Legacy Attributes (L-bit) 1 RSVP-TE (R-bit) 2 Segment Routing Traffic Engineering (S-bit) 3 Loop Free Alternate (F-bit) 4-7 Unassigned 8-15 Reserved for User Defined Application Use This document requests a new IANA registry be created to control the assignment of sub-TLV types for the application specific SRLG TLV. The suggested name of the new registry is "Sub-TLVs for TLV 238". The registration procedure is "Expert Review" as defined in [RFC5226]. The following assignments are made by this document: Value Description --------------------------------------------------------- 4 Link Local/Remote Identifiers (see [RFC5307]) 6 IPv4 interface address (see [RFC5305]) 8 IPv4 neighbor address (see [RFC5305]) 12 IPv6 Interface Address (see [RFC6119]) 13 IPv6 Neighbor Address (see [RFC6119]) Ginsberg, et al. Expires December 2, 2017 [Page 11] Internet-Draft draft-ginsberg-isis-te-app May 2017 7. Security Considerations Security concerns for IS-IS are addressed in [ISO10589, [RFC5304], and [RFC5310]. 8. Acknowledgements The authors would like to thank John Drake and Acee Lindem for their careful review and content suggestions. 9. References 9.1. Normative References [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, DOI 10.17487/RFC2119, March 1997, . [RFC5226] Narten, T. and H. Alvestrand, "Guidelines for Writing an IANA Considerations Section in RFCs", BCP 26, RFC 5226, DOI 10.17487/RFC5226, May 2008, . [RFC5304] Li, T. and R. Atkinson, "IS-IS Cryptographic Authentication", RFC 5304, DOI 10.17487/RFC5304, October 2008, . [RFC5305] Li, T. and H. Smit, "IS-IS Extensions for Traffic Engineering", RFC 5305, DOI 10.17487/RFC5305, October 2008, . [RFC5307] Kompella, K., Ed. and Y. Rekhter, Ed., "IS-IS Extensions in Support of Generalized Multi-Protocol Label Switching (GMPLS)", RFC 5307, DOI 10.17487/RFC5307, October 2008, . [RFC5310] Bhatia, M., Manral, V., Li, T., Atkinson, R., White, R., and M. Fanto, "IS-IS Generic Cryptographic Authentication", RFC 5310, DOI 10.17487/RFC5310, February 2009, . [RFC6119] Harrison, J., Berger, J., and M. Bartlett, "IPv6 Traffic Engineering in IS-IS", RFC 6119, DOI 10.17487/RFC6119, February 2011, . Ginsberg, et al. Expires December 2, 2017 [Page 12] Internet-Draft draft-ginsberg-isis-te-app May 2017 [RFC7810] Previdi, S., Ed., Giacalone, S., Ward, D., Drake, J., and Q. Wu, "IS-IS Traffic Engineering (TE) Metric Extensions", RFC 7810, DOI 10.17487/RFC7810, May 2016, . 9.2. Informative References [RFC7855] Previdi, S., Ed., Filsfils, C., Ed., Decraene, B., Litkowski, S., Horneffer, M., and R. Shakir, "Source Packet Routing in Networking (SPRING) Problem Statement and Requirements", RFC 7855, DOI 10.17487/RFC7855, May 2016, . Authors' Addresses Les Ginsberg Cisco Systems 821 Alder Drive Milpitas, CA 95035 USA Email: ginsberg@cisco.com Peter Psenak Cisco Systems Apollo Business Center Mlynske nivy 43 Bratislava 821 09 Slovakia Email: ppsenak@cisco.com Stefano Previdi Cisco Systems Via Del Serafico 200 Rome 0144 Italy Email: sprevidi@cisco.com Ginsberg, et al. Expires December 2, 2017 [Page 13] Internet-Draft draft-ginsberg-isis-te-app May 2017 Wim Henderickx Nokia Copernicuslaan 50 Antwerp 2018 94089 Belgium Email: wim.henderickx@nokia.com Ginsberg, et al. Expires December 2, 2017 [Page 14]