LSR Working Group P. Psenak, Ed. Internet-Draft Cisco Systems, Inc. Intended status: Standards Track A. Lindem Expires: April 20, 2019 L. Ginsberg Cisco Systems W. Henderickx Nokia J. Tantsura Nuage Networks H. Gredler RtBrick Inc. J. Drake Juniper Networks October 17, 2018 OSPF Link Traffic Engineering (TE) Attribute Reuse draft-ietf-ospf-te-link-attr-reuse-05.txt Abstract Various link attributes have been defined in OSPF in the context of the MPLS Traffic Engineering (TE) and GMPLS. Many of these link attributes can be used for applications other than MPLS Traffic Engineering or GMPLS. This document defines how to distribute such attributes in OSPFv2 and OSPFv3 for applications other than MPLS Traffic Engineering or GMPLS. 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 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 20, 2019. Psenak, et al. Expires April 20, 2019 [Page 1] Internet-Draft OSPF Link TE Attributes Reuse October 2018 Copyright Notice Copyright (c) 2018 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 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. This document may contain material from IETF Documents or IETF Contributions published or made publicly available before November 10, 2008. The person(s) controlling the copyright in some of this material may not have granted the IETF Trust the right to allow modifications of such material outside the IETF Standards Process. Without obtaining an adequate license from the person(s) controlling the copyright in such materials, this document may not be modified outside the IETF Standards Process, and derivative works of it may not be created outside the IETF Standards Process, except to format it for publication as an RFC or to translate it into languages other than English. Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3 1.1. Requirements notation . . . . . . . . . . . . . . . . . . 4 2. Link attributes examples . . . . . . . . . . . . . . . . . . 4 3. Advertising Link Attributes . . . . . . . . . . . . . . . . . 4 3.1. OSPFv2 TE Opaque LSA and OSPFv3 Intra-Area-TE-LSA . . . . 4 3.2. OSPFv2 Extended Link Opaque LSA and OSPFv3 E-Router-LSA . 5 3.3. Selected Approach . . . . . . . . . . . . . . . . . . . . 6 4. Reused TE link attributes . . . . . . . . . . . . . . . . . . 6 4.1. Shared Risk Link Group (SRLG) . . . . . . . . . . . . . . 6 4.2. Extended Metrics . . . . . . . . . . . . . . . . . . . . 7 4.3. Traffic Engineering Metric . . . . . . . . . . . . . . . 8 4.4. Administrative Group . . . . . . . . . . . . . . . . . . 8 5. Advertisement of Application Specific Values . . . . . . . . 8 6. Maximum Link Bandwidth . . . . . . . . . . . . . . . . . . . 11 7. Local Interface IPv6 Address Sub-TLV . . . . . . . . . . . . 12 8. Remote Interface IPv6 Address Sub-TLV . . . . . . . . . . . . 12 9. Deployment Considerations . . . . . . . . . . . . . . . . . . 12 10. Attribute Advertisements and Enablement . . . . . . . . . . . 12 11. Backward Compatibility . . . . . . . . . . . . . . . . . . . 13 Psenak, et al. Expires April 20, 2019 [Page 2] Internet-Draft OSPF Link TE Attributes Reuse October 2018 12. Security Considerations . . . . . . . . . . . . . . . . . . . 14 13. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 14 13.1. OSPFv2 . . . . . . . . . . . . . . . . . . . . . . . . . 14 13.2. OSPFv3 . . . . . . . . . . . . . . . . . . . . . . . . . 15 14. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 16 15. References . . . . . . . . . . . . . . . . . . . . . . . . . 16 15.1. Normative References . . . . . . . . . . . . . . . . . . 16 15.2. Informative References . . . . . . . . . . . . . . . . . 17 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 18 1. Introduction Various link attributes have been defined in OSPFv2 [RFC2328] and OSPFv3 [RFC5340] in the context of the MPLS traffic engineering and GMPLS. All these attributes are distributed by OSPFv2 as sub-TLVs of the Link-TLV advertised in the OSPFv2 TE Opaque LSA [RFC3630]. In OSPFv3, they are distributed as sub-TLVs of the Link-TLV advertised in the OSPFv3 Intra-Area-TE-LSA as defined in [RFC5329]. Many of these link attributes are useful outside of traditional MPLS Traffic Engineering or GMPLS. This brings its own set of problems, in particular how to distribute these link attributes in OSPFv2 and OSPFv3 when MPLS TE and GMPLS are not deployed or are deployed in parallel with other applications that use these link attributes. [RFC7855] discusses use cases/requirements for SR. Included among these use cases is SRTE. 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 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 should minimize advertising duplicate link/attribute when possible. Psenak, et al. Expires April 20, 2019 [Page 3] Internet-Draft OSPF Link TE Attributes Reuse October 2018 1.1. Requirements notation 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 [RFC2119]. 2. Link attributes examples This section lists some of the link attributes originally defined for MPLS Traffic Engineering that can be used for other applications in OSPFv2 and OSPFv3. The list doesn't necessarily contain all the required attributes. 1. Remote Interface IP address [RFC3630] - OSPFv2 currently cannot distinguish between parallel links between two OSPFv2 routers. As a result, the two-way connectivity check performed during SPF may succeed when the two routers disagree on which of the links to use for data traffic. 2. Link Local/Remote Identifiers - [RFC4203] - Used for the two-way connectivity check for parallel unnumbered links. Also used for identifying adjacencies for unnumbered links in Segment Routing traffic engineering. 3. Shared Risk Link Group (SRLG) [RFC4203] - In IPFRR, the SRLG is used to compute diverse backup paths [RFC5714]. 4. Unidirectional Link Delay/Loss Metrics [RFC7471] - Could be used for the shortest path first (SPF) computation using alternate metrics within an OSPF area. 3. Advertising Link Attributes This section outlines possible approaches for advertising link attributes originally defined for MPLS Traffic Engineering or GMPLS when they are used for other applications. 3.1. OSPFv2 TE Opaque LSA and OSPFv3 Intra-Area-TE-LSA One approach for advertising link attributes is to continue to use the OSPFv2 TE Opaque LSA [RFC3630] or the OSPFv3 Intra-Area-TE-LSA [RFC5329]. There are several problems with this approach: 1. Whenever the link is advertised in an OSPFv2 TE Opaque LSA or in an OSPFv3 Intra-Area-TE-LSA, the link becomes a part of the TE topology, which may not match IP routed topology. By making the link part of the TE topology, remote nodes may mistakenly believe Psenak, et al. Expires April 20, 2019 [Page 4] Internet-Draft OSPF Link TE Attributes Reuse October 2018 that the link is available for MPLS TE or GMPLS, when, in fact, MPLS is not enabled on the link. 2. The OSPFv2 TE Opaque LSA and OSPFv3 Intra-Area-TE-LSA advertise link attributes that are not used or required by MPLS TE or GMPLS. There is no mechanism in these TE LSAs to indicate which of the link attributes are passed to the MPLS TE application and which are used by other applications including OSPF itself. 3. Link attributes used for non-TE applications are partitioned across multiple LSAs - the TE Opaque LSA and the Extended Link Opaque LSA in OSPFv2 and the OSPFv3 Intra-Area-TE-LSA and OSPFv3 Extended LSA Router-Link TLV [RFC8362] in OSPFv3. This partitioning will require implementations to lookup multiple LSAs to extract link attributes for a single link, bringing needless complexity to OSPF implementations. The advantage of this approach is that there is no additional standardization requirement to advertise the TE/GMPL attributes for other applications. Additionally, link attributes are only advertised once when both OSPF TE and other applications are deployed on the same link. This is not expected to be a common deployment scenario. 3.2. OSPFv2 Extended Link Opaque LSA and OSPFv3 E-Router-LSA An alternative approach for advertising link attributes is to use Extended Link Opaque LSAs as defined in [RFC7684] for OSPFv2 and Extended Router-LSAs [RFC8362] for OSPFv3. These LSAs were defined as a generic containers for distribution of the extended link attributes. There are several advantages in using them: 1. Advertisement of the link attributes does not make the link part of the TE topology. It avoids any conflicts and is fully compatible with the [RFC3630] and [RFC5329]. 2. The OSPFv2 TE Opaque LSA and OSPFv3 Intra-Area-TE-LSA remains truly opaque to OSPFv2 and OSPFv3 as originally defined in [RFC3630] and [RFC5329] respectively. Their contents are not inspected by OSPF, that act as a pure transport. 3. There is clear distinction between link attributes used by TE and link attributes used by other OSPFv2 or OSPFv3 applications. 4. All link attributes that are used by other applications are advertised in a single LSA, the Extended Link Opaque LSA in OSPFv2 or the OSPFv3 E-Router-LSA [RFC8362] in OSPFv3. Psenak, et al. Expires April 20, 2019 [Page 5] Internet-Draft OSPF Link TE Attributes Reuse October 2018 The disadvantage of this approach is that in rare cases, the same link attribute is advertised in both the TE Opaque and Extended Link Attribute LSAs in OSPFv2 or the Intra-Area-TE-LSA and E-Router-LSA in OSPFv3. Additionally, there will be additional standardization effort. However, this could also be viewed as an advantage as the non-TE use cases for the TE link attributes are documented and validated by the LSR working group. 3.3. Selected Approach It is RECOMMENDED to use the Extended Link Opaque LSA [RFC7684] and E-Router-LSA [RFC8362] to advertise any link attributes used for non- TE applications in OSPFv2 or OSPFv3 respectively, including those that have been originally defined for TE applications. It is also RECOMMENDED that TE link attributes used for RSVP-TE/GMPLS continue to use OSPFv2 TE Opaque LSA [RFC3630] and OSPFv3 Intra-Area- TE-LSA [RFC5329]. It is also RECOMMENDED to keep the format of the link attribute TLVs that have been defined for TE applications unchanged even when they are used for non-TE applications. Finally, it is RECOMMENDED to allocate unique code points for these TE link attribute TLVs in the OSPFv2 Extended Link TLV Sub-TLV Registry [RFC7684] and in the OSPFv3 Extended LSA Sub-TLV Registry [RFC8362]. For each reused TLV, the code point will be defined in an IETF document along with the expected use-case(s). 4. Reused TE link attributes This section defines the use case and code points for the OSPFv2 Extended Link TLV Sub-TLV Registry and OSPFv3 Extended LSA Sub-TLV Registry for some of the link attributes that have been originally defined for TE or GMPLS. Remote interface IP address and Link Local/Remote Identifiers have been added as sub-TLVs of OSPFv2 Extended Link TLV by [RFC8379]. Link Local/Remote Identifiers are already included in the OSPFv3 Router-Link TLV [RFC8362]. 4.1. Shared Risk Link Group (SRLG) The SRLG of a link can be used in IPFRR to compute a backup path that does not share any SRLG group with the protected link. To advertise the SRLG of the link in the OSPFv2 Extended Link TLV, the same format for the sub-TLV defined in section 1.3 of [RFC4203] Psenak, et al. Expires April 20, 2019 [Page 6] Internet-Draft OSPF Link TE Attributes Reuse October 2018 is used and TLV type TBD1 is used. Similarly, for OSPFv3 to advertise the SRLG in the OSPFv3 Router-Link TLV, TLV type TBD2 is used. 4.2. Extended Metrics [RFC3630] defines several link bandwidth types. [RFC7471] defines extended link metrics that are based on link bandwidth, delay and loss characteristics. All these can be used to compute best paths within an OSPF area to satisfy requirements for bandwidth, delay (nominal or worst case) or loss. To advertise extended link metrics in the OSPFv2 Extended Link TLV, the same format for the sub-TLVs defined in [RFC7471] is used with the following TLV types: TBD3 - Unidirectional Link Delay TBD4 - Min/Max Unidirectional Link Delay TBD5 - Unidirectional Delay Variation TBD6 - Unidirectional Link Loss TBD7 - Unidirectional Residual Bandwidth TBD8 - Unidirectional Available Bandwidth TBD9 - Unidirectional Utilized Bandwidth To advertise extended link metrics in the OSPFv3 Extended LSA Router- Link TLV, the same format for the sub-TLVs defined in [RFC7471] is used with the following TLV types: TBD10 - Unidirectional Link Delay TBD11 - Min/Max Unidirectional Link Delay TBD12 - Unidirectional Delay Variation TBD13 - Unidirectional Link Loss TBD14 - Unidirectional Residual Bandwidth TBD15 - Unidirectional Available Bandwidth TBD16 - Unidirectional Utilized Bandwidth Psenak, et al. Expires April 20, 2019 [Page 7] Internet-Draft OSPF Link TE Attributes Reuse October 2018 4.3. Traffic Engineering Metric [RFC3630] defines Traffic Engineering Metric. To advertise the Traffic Engineering Metric in the OSPFv2 Extended Link TLV, the same format for the sub-TLV defined in section 2.5.5 of [RFC3630] is used and TLV type TBD27 is used. Similarly, for OSPFv3 to advertise the Traffic Engineering Metric in the OSPFv3 Router-Link TLV, TLV type TBD28 is used. 4.4. Administrative Group [RFC3630] and [RFC7308] define the Administrative Group and Extended Administrative Group sub-TLVs respectively. One use case where advertisement of the Extended Administrative Group(s) for a link is required is described in [I-D.ietf-lsr-flex-algo]. To advertise the Administrative Group and Extended Administrative Group in the OSPFv2 Extended Link TLV, the same format for the sub- TLVs defined in [RFC3630] and [RFC7308] is used with the following TLV types: TBD17 - Administrative Group TBD18 - Extended Administrative Group To advertise Administrative Group and Extended Administrative Group in the OSPFv3 Router-Link TLV, the same format for the sub-TLVs defined in [RFC3630] and [RFC7308] is used with the following TLV types: TBD19 - Administrative Group TBD20 - Extended Administrative Group 5. Advertisement of Application Specific Values Multiple applications can utilize link attributes that are advertised by OSPF. Some examples of applications using the link attributes are Segment Routing Traffic Engineering and LFA [RFC5286]. In some cases the link attribute MAY have different values for different applications. An example could be SRLG [Section 4.1], where values used by LFA could be different then the values used by Segment Routing Traffic Engineering. Psenak, et al. Expires April 20, 2019 [Page 8] Internet-Draft OSPF Link TE Attributes Reuse October 2018 To allow advertisement of the application specific values of the link attribute, a new Application Specific Link Attributes (ASLA) sub-TLV is defined. The ASLA sub-TLV is a sub-TLV of the OSPFv2 Extended Link TLV [RFC7471] and OSPFv3 Router-Link TLV [RFC8362]. The ASLA sub-TLV is an optional sub-TLV and can appear multiple times in the OSPFv2 Extended Link TLV and OSPFv3 Router-Link TLV. It has the following format: 0 1 2 3 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Type | Length | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | SABML | UDABML | Reserved | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Standard Application Bit-Mask | +- -+ | ... | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | User Defined Application Bit-Mask | +- -+ | ... | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Link Attribute sub-sub-TLVs | +- -+ | ... | where: Type: TBD21 (OSPFv2), TBD22 (OSPFv3) Length: variable SABML: Standard Application Bit-Mask Length. If the Standard Application Bit-Mask is not present, the Standard Application Bit- Mask Length MUST be set to 0. UDABML: User Defined Application Bit-Mask Length. If the User Defined Application Bit-Mask is not present, the User Defined Application Bit-Mask Length MUST be set to 0. Standard Application Bit-Mask: Optional set of bits, where each bit represents a single standard application. Bits are defined in [I-D.ietf-isis-te-app], which also request a new IANA "Link Attribute Applications" registry under "Interior Gateway Protocol (IGP) Parameters" for them. The bits are repeated here for informational purpose: Psenak, et al. Expires April 20, 2019 [Page 9] Internet-Draft OSPF Link TE Attributes Reuse October 2018 Bit-0: RSVP Traffic Engineering Bit-1: Segment Routing Traffic Engineering Bit-2: Loop Free Alternate (LFA). Includes all LFA types Bit-3: Flexible Algorithm User Defined Application Bit-Mask: Optional set of bits, where each bit represents a single user defined application. Standard Application Bits are defined/sent starting with Bit 0. Additional bit definitions that are 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. User Defined Application bits have no relationship to Standard Application 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 of them. Undefined bits in both Bit-Masks 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. If the link attribute advertisement is limited to be used by a specific set of applications, corresponding Bit-Masks MUST be present and application specific bit(s) MUST be set for all applications that use the link attributes advertised in the ASLA sub-TLV. Application Bit-Masks apply to all link attributes that support application specific values and are advertised in the ASLA sub-TLV. The advantage of not making the Application Bit-Masks part of the attribute advertisement itself is that we can keep the format of the link attributes that have been defined previously and reuse the same format when advertising them in the ASLA sub-TLV. When neither the Standard Application Bits nor the User Defined Application bits are set (i.e., both SABML and UDABML are 0) in the ASLA sub-TLV, then the link attributes included in it MUST be considered as being applicable to all applications. If, however, another advertisement of the same link attribute includes any Application Bit-Mask in the ASLA sub-TLV, applications that are listed in the Application Bit-Masks of such ASLA sub-TLV SHOULD use the attribute advertisement which has the application specific bit set in the Application Bit-Masks. Psenak, et al. Expires April 20, 2019 [Page 10] Internet-Draft OSPF Link TE Attributes Reuse October 2018 If the same application is listed in the Application Bit-Masks of more then one ASLA sub-TLV, the application SHOULD use the first advertisement and ignore any subsequent advertisements of the same attribute. This situation SHOULD be logged as an error. This document defines the initial set of link attributes that MUST use ASLA sub-TLV if advertised in the OSPFv2 Extended Link TLV or in the OSPFv3 Router-Link TLV. If the ASLA sub-TLV includes any link attribute(s) NOT listed below, they MUST be ignored. Documents which define new link attributes MUST state whether the new attributes support application specific values and as such MUST be advertised in an ASLA sub-TLV. The link attributes that MUST be advertised in ASLA sub-TLVs are: - Shared Risk Link Group - Unidirectional Link Delay - Min/Max Unidirectional Link Delay - Unidirectional Delay Variation - Unidirectional Link Loss - Unidirectional Residual Bandwidth - Unidirectional Available Bandwidth - Unidirectional Utilized Bandwidth - Administrative Group - Extended Administrative Group - Traffic Engineering Metric 6. Maximum Link Bandwidth Maximum link bandwidth is an application independent attribute of the link that is defined in [RFC3630]. Because it is an application independent attribute, it MUST NOT be advertised in ASLA sub-TLV. Instead, it MAY be advertised as a sub-TLV of the Extended Link Opaque LSA Extended Link TLV in OSPFv2 [RFC7684] or sub-TLV of OSPFv3 E-Router-LSA Router-Link TLV in OSPFv3 [RFC8362]. To advertise the Maximum link bandwidth in the OSPFv2 Extended Link TLV, the same format for sub-TLV defined in [RFC3630] is used with TLV type TBD23. Psenak, et al. Expires April 20, 2019 [Page 11] Internet-Draft OSPF Link TE Attributes Reuse October 2018 To advertise the Maximum link bandwidth in the OSPFv3 Router-Link TLV, the same format for sub-TLV defined in [RFC3630] is used with TLV type TBD24. 7. Local Interface IPv6 Address Sub-TLV The Local Interface IPv6 Address Sub-TLV is an application independent attribute of the link that is defined in [RFC5329]. Because it is an application independent attribute, it MUST NOT be advertised in the ASLA sub-TLV. Instead, it MAY be advertised as a sub-TLV of the OSPFv3 E-Router-LSA Router-Link TLV [RFC8362]. To advertise the Local Interface IPv6 Address Sub-TLV in the OSPFv3 Router-Link TLV, the same format for sub-TLV defined in [RFC5329] is used with TLV type TBD25. 8. Remote Interface IPv6 Address Sub-TLV The Remote Interface IPv6 Address Sub-TLV is an application independent attribute of the link that is defined in [RFC5329]. Because it is an application independent attribute, it MUST NOT be advertised in the ASLA sub-TLV. Instead, it MAY be advertised as a sub-TLV of the OSPFv3 E-Router-LSA Router-Link TLV [RFC8362]. To advertise the Remote Interface IPv6 Address Sub-TLV in the OSPFv3 Router-Link TLV, the same format for sub-TLV defined in [RFC5329] is used with TLV type TBD26. 9. Deployment Considerations If link attributes are advertised associated with zero length application 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. 10. Attribute Advertisements and Enablement 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 Psenak, et al. Expires April 20, 2019 [Page 12] Internet-Draft OSPF Link TE Attributes Reuse October 2018 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. 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. Enablement is controlled by local configuration. In the case of Flexible Algorithm, advertisement of application specific link attributes does NOT indicate enablement of Flexible Algorithm on that link. Rather the attributes are used to determine what links are included/excluded in the algorithm specific constrained SPF. This is fully specified in [I-D.ietf-lsr-flex-algo]. 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 Bit Mask and the User Defined Application Bit Mask are not present Section 5. This supports 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. 11. Backward Compatibility Link attributes may be concurrently advertised in both the TE Opaque LSA and the Extended Link Opaque LSA in OSPFv2 and the OSPFv3 Intra- Area-TE-LSA and OSPFv3 Extended LSA Router-Link TLV in OSPFv3. In fact, there is at least one OSPF implementation that utilizes the link attributes advertised in TE Opaque LSAs [RFC3630] for Non-RSVP Psenak, et al. Expires April 20, 2019 [Page 13] Internet-Draft OSPF Link TE Attributes Reuse October 2018 TE applications. For example, this implementation of LFA and remote LFA utilizes links attributes such as Shared Risk Link Groups (SRLG) [RFC4203] and Admin Group [[RFC3630] advertised in TE Opaque LSAs. These applications are described in [RFC5286], [RFC7490], [RFC7916] and [RFC8102]. When an OSPF routing domain includes routers using link attributes from the OSPFv2 TE Opaque LSAs or the OSPFv3 Intra-Area-TE-LSA for Non-RSVP TE applications such as LFA, OSPF routers in that domain SHOULD continue to advertise such OSPFv2 TE Opaque LSAs or the OSPFv3 Intra-Area-TE-LSA. If there are also OSPF routers using the link attributes described herein for any other application, OSPF routers in the routing domain will also need to advertise these attributes in OSPFv2 Extended Link Attributes LSAs or OSPFv3 E-Router-LSA. In such a deployment, the advertised attributes SHOULD be the same and Non- RSVP application access to link attributes is a matter of local policy. 12. Security Considerations Implementations must assure that malformed TLV and Sub-TLV permutations do not result in errors that cause hard OSPF failures. 13. IANA Considerations 13.1. OSPFv2 OSPFv2 Extended Link TLV Sub-TLVs registry [RFC7684] defines sub-TLVs at any level of nesting for OSPFv2 Extended Link TLVs. This specification updates OSPFv2 Extended Link TLV sub-TLVs registry with the following TLV types: TBD21 (10 Recommended) - Application Specific Link Attributes TBD1 (11 Recommended) - Shared Risk Link Group TBD3 (12 Recommended) - Unidirectional Link Delay TBD4 (13 Recommended) - Min/Max Unidirectional Link Delay TBD5 (14 Recommended) - Unidirectional Delay Variation TBD6 (15 Recommended) - Unidirectional Link Loss TBD7 (16 Recommended) - Unidirectional Residual Bandwidth TBD8 (17 Recommended) - Unidirectional Available Bandwidth Psenak, et al. Expires April 20, 2019 [Page 14] Internet-Draft OSPF Link TE Attributes Reuse October 2018 TBD9 (18 Recommended) - Unidirectional Utilized Bandwidth TBD9 (19 Recommended) - Administrative Group TBD17 (20 Recommended) - Extended Administrative Group TBD23 (21 Recommended) - Maximum Link Bandwidth TBD27 (22 Recommended) - Traffic Engineering Metric 13.2. OSPFv3 OSPFv3 Extended LSA Sub-TLV Registry [RFC8362] defines sub-TLVs at any level of nesting for OSPFv3 Extended LSAs. This specification updates OSPFv3 Extended LSA Sub-TLV Registry with the following TLV types: TBD22 (9 Recommended) - Application Specific Link Attributes TBD2 (10 Recommended) - Shared Risk Link Group TBD10 (11 Recommended) - Unidirectional Link Delay TBD11 (12 Recommended) - Min/Max Unidirectional Link Delay TBD12 (13 Recommended) - Unidirectional Delay Variation TBD13 (14 Recommended) - Unidirectional Link Loss TBD14 (15 Recommended) - Unidirectional Residual Bandwidth TBD15 (16 Recommended) - Unidirectional Available Bandwidth TBD16 (17 Recommended) - Unidirectional Utilized Bandwidth TBD19 (18 Recommended) - Administrative Group TBD20 (19 Recommended) - Extended Administrative Group TBD24 (20 Recommended) - Maximum Link Bandwidth TBD25 (21 Recommended) - Local Interface IPv6 Address Sub-TLV TBD26 (22 Recommended) - Local Interface IPv6 Address Sub-TLV TBD28 (23 Recommended) - Traffic Engineering Metric Psenak, et al. Expires April 20, 2019 [Page 15] Internet-Draft OSPF Link TE Attributes Reuse October 2018 14. Acknowledgments Thanks to Chris Bowers for his review and comments. 15. References 15.1. 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, . [RFC3630] Katz, D., Kompella, K., and D. Yeung, "Traffic Engineering (TE) Extensions to OSPF Version 2", RFC 3630, DOI 10.17487/RFC3630, September 2003, . [RFC5329] Ishiguro, K., Manral, V., Davey, A., and A. Lindem, Ed., "Traffic Engineering Extensions to OSPF Version 3", RFC 5329, DOI 10.17487/RFC5329, September 2008, . [RFC5340] Coltun, R., Ferguson, D., Moy, J., and A. Lindem, "OSPF for IPv6", RFC 5340, DOI 10.17487/RFC5340, July 2008, . [RFC5714] Shand, M. and S. Bryant, "IP Fast Reroute Framework", RFC 5714, DOI 10.17487/RFC5714, January 2010, . [RFC7308] Osborne, E., "Extended Administrative Groups in MPLS Traffic Engineering (MPLS-TE)", RFC 7308, DOI 10.17487/RFC7308, July 2014, . [RFC7684] Psenak, P., Gredler, H., Shakir, R., Henderickx, W., Tantsura, J., and A. Lindem, "OSPFv2 Prefix/Link Attribute Advertisement", RFC 7684, DOI 10.17487/RFC7684, November 2015, . [RFC8362] Lindem, A., Roy, A., Goethals, D., Reddy Vallem, V., and F. Baker, "OSPFv3 Link State Advertisement (LSA) Extensibility", RFC 8362, DOI 10.17487/RFC8362, April 2018, . Psenak, et al. Expires April 20, 2019 [Page 16] Internet-Draft OSPF Link TE Attributes Reuse October 2018 15.2. Informative References [I-D.ietf-idr-ls-distribution] Gredler, H., Medved, J., Previdi, S., Farrel, A., and S. Ray, "North-Bound Distribution of Link-State and TE Information using BGP", draft-ietf-idr-ls-distribution-13 (work in progress), October 2015. [I-D.ietf-isis-te-app] Ginsberg, L., Psenak, P., Previdi, S., Henderickx, W., and J. Drake, "IS-IS TE Attributes per application", draft- ietf-isis-te-app-05 (work in progress), October 2018. [I-D.ietf-lsr-flex-algo] Psenak, P., Hegde, S., Filsfils, C., Talaulikar, K., and A. Gulko, "IGP Flexible Algorithm", draft-ietf-lsr-flex- algo-00 (work in progress), May 2018. [I-D.ietf-ospf-segment-routing-extensions] Psenak, P., Previdi, S., Filsfils, C., Gredler, H., Shakir, R., Henderickx, W., and J. Tantsura, "OSPF Extensions for Segment Routing", draft-ietf-ospf-segment- routing-extensions-25 (work in progress), April 2018. [RFC2328] Moy, J., "OSPF Version 2", STD 54, RFC 2328, DOI 10.17487/RFC2328, April 1998, . [RFC4203] Kompella, K., Ed. and Y. Rekhter, Ed., "OSPF Extensions in Support of Generalized Multi-Protocol Label Switching (GMPLS)", RFC 4203, DOI 10.17487/RFC4203, October 2005, . [RFC5286] Atlas, A., Ed. and A. Zinin, Ed., "Basic Specification for IP Fast Reroute: Loop-Free Alternates", RFC 5286, DOI 10.17487/RFC5286, September 2008, . [RFC7471] Giacalone, S., Ward, D., Drake, J., Atlas, A., and S. Previdi, "OSPF Traffic Engineering (TE) Metric Extensions", RFC 7471, DOI 10.17487/RFC7471, March 2015, . [RFC7490] Bryant, S., Filsfils, C., Previdi, S., Shand, M., and N. So, "Remote Loop-Free Alternate (LFA) Fast Reroute (FRR)", RFC 7490, DOI 10.17487/RFC7490, April 2015, . Psenak, et al. Expires April 20, 2019 [Page 17] Internet-Draft OSPF Link TE Attributes Reuse October 2018 [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, . [RFC7916] Litkowski, S., Ed., Decraene, B., Filsfils, C., Raza, K., Horneffer, M., and P. Sarkar, "Operational Management of Loop-Free Alternates", RFC 7916, DOI 10.17487/RFC7916, July 2016, . [RFC8102] Sarkar, P., Ed., Hegde, S., Bowers, C., Gredler, H., and S. Litkowski, "Remote-LFA Node Protection and Manageability", RFC 8102, DOI 10.17487/RFC8102, March 2017, . [RFC8379] Hegde, S., Sarkar, P., Gredler, H., Nanduri, M., and L. Jalil, "OSPF Graceful Link Shutdown", RFC 8379, DOI 10.17487/RFC8379, May 2018, . Authors' Addresses Peter Psenak (editor) Cisco Systems, Inc. Eurovea Centre, Central 3 Pribinova Street 10 Bratislava 81109 Slovakia Email: ppsenak@cisco.com Acee Lindem Cisco Systems 301 Midenhall Way Cary, NC 27513 USA Email: acee@cisco.com Psenak, et al. Expires April 20, 2019 [Page 18] Internet-Draft OSPF Link TE Attributes Reuse October 2018 Les Ginsberg Cisco Systems 821 Alder Drive MILPITAS, CA 95035 USA Email: ginsberg@cisco.com Wim Henderickx Nokia Copernicuslaan 50 Antwerp, 2018 94089 Belgium Email: wim.henderickx@nokia.com Jeff Tantsura Nuage Networks US Email: jefftant.ietf@gmail.com Hannes Gredler RtBrick Inc. Email: hannes@rtbrick.com John Drake Juniper Networks Email: jdrake@juniper.net Psenak, et al. 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