OSPFv2 Link Traffic Engineering (TE) Attribute Reuse
The information below is for an old version of the document.
This is an older version of an Internet-Draft that was ultimately published as RFC 8920.
|Authors||Peter Psenak , Acee Lindem , Les Ginsberg , Wim Henderickx , Jeff Tantsura , Hannes Gredler|
|RFC stream||Internet Engineering Task Force (IETF)|
OPSDIR Last Call review (of -12) Not Ready
RTGDIR Last Call review (of -12) Has Nits
GENART Last Call review (of -12) Not Ready
RTGDIR Last Call review (of -07) Has Issues
|Additional resources||Mailing list discussion|
|Stream||WG state||WG Document|
|IESG||IESG state||I-D Exists|
|Send notices to||(None)|
Network Working Group P. Psenak Internet-Draft A. Lindem Intended status: Standards Track L. Ginsberg Expires: February 22, 2018 Cisco Systems W. Henderickx Nokia J. Tantsura Individual H. Gredler RtBrick Inc. August 21, 2017 OSPFv2 Link Traffic Engineering (TE) Attribute Reuse draft-ietf-ospf-te-link-attr-reuse-00.txt Abstract Various link attributes have been defined in OSPFv2 in the context of the MPLS Traffic Engineering (TE) and GMPLS. Many of these link attributes can be used for purposes other than MPLS Traffic Engineering or GMPLS. This documents defines how to distribute such attributes in OSPFv2 for applications other than MPLS Traffic Engineering or GMPLS purposes. 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." This Internet-Draft will expire on February 22, 2018. Copyright Notice Copyright (c) 2017 IETF Trust and the persons identified as the document authors. All rights reserved. Psenak, et al. Expires February 22, 2018 [Page 1] Internet-Draft OSPFv2 Link TE Attributes Reuse August 2017 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. 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 . . . . . . . . . . . . . . . . . . 3 2. Link attributes examples . . . . . . . . . . . . . . . . . . 3 3. Advertising Link Attributes . . . . . . . . . . . . . . . . . 4 3.1. TE Opaque LSA . . . . . . . . . . . . . . . . . . . . . . 4 3.2. Extended Link Opaque LSA . . . . . . . . . . . . . . . . 5 3.3. Selected Approach . . . . . . . . . . . . . . . . . . . . 5 4. Reused TE link attributes . . . . . . . . . . . . . . . . . . 6 4.1. Remote interface IP address . . . . . . . . . . . . . . . 6 4.2. Link Local/Remote Identifiers . . . . . . . . . . . . . . 6 4.3. Shared Risk Link Group (SRLG) . . . . . . . . . . . . . . 7 4.4. Extended Metrics . . . . . . . . . . . . . . . . . . . . 7 5. Advertisement of Application Specific Values . . . . . . . . 7 6. Deployment Considerations . . . . . . . . . . . . . . . . . . 10 7. Attribute Advertisements and Enablement . . . . . . . . . . . 10 8. Backward Compatibility . . . . . . . . . . . . . . . . . . . 11 9. Security Considerations . . . . . . . . . . . . . . . . . . . 11 10. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 12 11. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 12 12. References . . . . . . . . . . . . . . . . . . . . . . . . . 12 12.1. Normative References . . . . . . . . . . . . . . . . . . 12 12.2. Informative References . . . . . . . . . . . . . . . . . 13 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 14 Psenak, et al. Expires February 22, 2018 [Page 2] Internet-Draft OSPFv2 Link TE Attributes Reuse August 2017 1. Introduction Various link attributes have been defined in OSPFv2 [RFC2328] 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]. Many of these link attributes are useful outside of the traditional MPLS Traffic Engineering or GMPLS. This brings its own set of problems, in particular how to distribute these link attributes in OSPFv2 when MPLS TE or 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. 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 purposes in OSPFv2. 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 Psenak, et al. Expires February 22, 2018 [Page 3] Internet-Draft OSPFv2 Link TE Attributes Reuse August 2017 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 purposes or GMPLS when they are used for other applications. 3.1. TE Opaque LSA One approach for advertising link attributes is to continue to use TE Opaque LSA ([RFC3630]). There are several problems with this approach: 1. Whenever the link is advertised in a TE Opaque 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 that the link is available for MPLS TE or GMPLS, when, in fact, MPLS is not enabled on the link. 2. The TE Opaque LSA carries link attributes that are not used or required by MPLS TE or GMPLS. There is no mechanism in a TE Opaque LSA to indicate which of the link attributes are passed to MPLS TE application and which are used by other applications including OSPFv2 itself. 3. Link attributes used for non-TE purposes are partitioned across multiple LSAs - the TE Opaque LSA and the Extended Link Opaque LSA. This partitioning will require implementations to lookup multiple LSAs to extract link attributes for a single link, bringing needless complexity to OSPFv2 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 Psenak, et al. Expires February 22, 2018 [Page 4] Internet-Draft OSPFv2 Link TE Attributes Reuse August 2017 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. Extended Link Opaque LSA An alternative approach for advertising link attributes is to use Extended Link Opaque LSAs as defined in [RFC7684]. This LSA was defined as a generic container for distribution of the extended link attributes. There are several advantages in using Extended Link LSA: 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]. 2. The TE Opaque LSA remains truly opaque to OSPFv2 as originally defined in [RFC3630]. Its content is not inspected by OSPFv2 and OSPFv2 acts as a pure transport. 3. There is clear distinction between link attributes used by TE and link attributes used by other OSPFv2 applications. 4. All link attributes that are used by OSPFv2 applications are advertised in a single LSA, the Extended Link Opaque LSA. 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. 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 OSPF working group. 3.3. Selected Approach It is RECOMMENDED to use the Extended Link Opaque LSA ([RFC7684] to advertise any link attributes used for non-TE purposes in OSPFv2, including those that have been originally defined for TE purposes. TE link attributes used for TE purposes continue to use TE Opaque LSA ([RFC3630]). It is also RECOMMENDED to keep the format of the link attribute TLVs that have been defined for TE purposes unchanged even when they are used for non-TE purposes. Finally, it is RECOMMENDED to allocate unique code points for link attribute TLVs that have been defined for TE purposes for the OSPFv2 Extended Link TLV Sub-TLV Registry as defined in [RFC7684]. For each Psenak, et al. Expires February 22, 2018 [Page 5] Internet-Draft OSPFv2 Link TE Attributes Reuse August 2017 reused TLV, the code point will be defined in an IETF document along with the expected usecase(s). 4. Reused TE link attributes This section defines the use case and code points for the OSPFv2 Extended Link TLV Sub-TLV Registry for some of the link attributes that have been originally defined for TE or GMPLS purposes. 4.1. Remote interface IP address The OSPFv2 description of an IP numbered point-to-point adjacency does not include the remote IP address. As described in Section 2, this makes the two-way connectivity check ambiguous in the presence of the parallel point-to-point links between two OSPFv2 routers. The Remote IP address of the link can also be used for Segment Routing traffic engineering to identify the link in a set of parallel links between two OSPFv2 routers [I-D.ietf-ospf-segment-routing-extensions]. Similarly, the remote IP address is useful in identifying individual parallel OSPF links advertised in BGP Link-State as described in [I-D.ietf-idr-ls-distribution]. To advertise the Remote interface IP address in the OSPFv2 Extended Link TLV, the same format of the sub-TLV as defined in section 2.5.4. of [RFC3630] is used and TLV type TBD1 is used. 4.2. Link Local/Remote Identifiers The OSPFv2 description of an IP unnumbered point-to-point adjacency does not include the remote link identifier. As described in Section 2, this makes the two-way connectivity check ambiguous in the presence of the parallel point-to-point IP unnumbered links between two OSPFv2 routers. The local and remote link identifiers can also be used for Segment Routing traffic engineering to identify the link in a set of parallel IP unnumbered links between two OSPFv2 routers [I-D.ietf-ospf-segment-routing-extensions]. Similarly, these identifiers are useful in identifying individual parallel OSPF links advertised in BGP Link-State as described in [I-D.ietf-idr-ls-distribution]. To advertise the link Local/Remote identifiers in the OSPFv2 Extended Link TLV, the same format of the sub-TLV as defined in section 1.1. of [RFC4203] is used and TLV type TBD2 is used. Psenak, et al. Expires February 22, 2018 [Page 6] Internet-Draft OSPFv2 Link TE Attributes Reuse August 2017 4.3. 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 of the sub-TLV as defined in section 1.3. of [RFC4203] is used and TLV type TBD3 is used. 4.4. 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 of the sub-TLVs as defined in [RFC7471] is used with following TLV types: TBD4 - Unidirectional Link Delay TBD5 - Min/Max Unidirectional Link Delay TBD6 - Unidirectional Delay Variation TBD7 - Unidirectional Link Loss TBD8 - Unidirectional Residual Bandwidth TBD9 - Unidirectional Available Bandwidth TBD10 - Unidirectional Utilized Bandwidth 5. Advertisement of Application Specific Values Multiple applications can utilize link attributes that are flooded by OSPFv2. Some examples of applications using the link attributes are Segment Routing Traffic Engineering and LFA [RFC5286]. In some cases the link attribute only has a single value that is applicable to all applications. An example is a Remote interface IP address [Section 4.1] or Link Local/Remote Identifiers [Section 4.2]. In some cases the link attribute MAY have different values for different applications. An example could be SRLG [Section 4.3], Psenak, et al. Expires February 22, 2018 [Page 7] Internet-Draft OSPFv2 Link TE Attributes Reuse August 2017 where values used by LFA could be different then the values used by Segment Routing Traffic Engineering. To allow advertisement of the application specific values of the link attribute, a new Extended Link Attribute sub-TLV of the Extended Link TLV [RFC7471] is defined. The Extended Link Attribute sub-TLV is an optional sub-TLV and can appear multiple times in the Extended Link TLV. It has 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: TBD11, suggested value 14 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. The following bits are defined by this document: Bit-0: RSVP Traffic Engineering Psenak, et al. Expires February 22, 2018 [Page 8] Internet-Draft OSPFv2 Link TE Attributes Reuse August 2017 Bit-1: Segment Routing Traffic Engineering Bit-2: Loop Free Alternate (LFA). Includes all LFA types. 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 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. 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 Extended Link Attribute sub-TLV. Application Bit-Masks apply to all link attributes that support application specific values and are advertised in the Extended Link Attribute 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 Extended Link Attribute sub-TLV. If the link attribute is advertised and there is no Application Bit- Mask present in the Extended Link Attribute Sub-TLV, the link attribute advertisement MAY be used by any application. If, however, another advertisement of the same link attribute includes any Application Bit-Mask in the Extended Link Attribute sub-TLV, applications that are listed in the Application Bit-Masks of such Extended Link Attribute sub-TLV SHOULD use the attribute advertisement which has the application specific bit set in the Application Bit-Masks. If the same application is listed in the Application Bit-Masks of more then one Extended Link Attribute sub-TLV, the application SHOULD Psenak, et al. Expires February 22, 2018 [Page 9] Internet-Draft OSPFv2 Link TE Attributes Reuse August 2017 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 set of link attributes for which the Application Bit-Masks may be advertised. If any of the Application Bit-Masks is included in the Extended Link Attribute sub-TLV that advertises any link attribute(s) NOT listed below, the Application Bit-Masks MUST NOT be used for such link attribute(s). It MUST be used for those attribute(s) that support application specific values. Documents which define new link attributes MUST state whether the new attributes support application specific values. The link attributes to which the Application Bit-Masks may apply 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 6. 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. 7. Attribute Advertisements and Enablement This document defines extensions to support the advertisement of application specific link attributes. The presence or absence of link attribute advertisements for a given application on a link does NOT indicate the state of enablement of that application on that Psenak, et al. Expires February 22, 2018 [Page 10] Internet-Draft OSPFv2 Link TE Attributes Reuse August 2017 link. Enablement of an application on a link is controlled by other means. For some applications, the concept of enablement is implicit. For example, SRTE implicitly is enabled on all links which are part of the Segment Routing enabled topology. Advertisement of link attributes supports constraints which may be applied when specifying an explicit path through that topology. For other applications enablement is controlled by local configuration. For example, use of a link as an LFA can be controlled by local enablement/disablement and/or the use of administrative tags. It is an application specific policy as to whether a given link can be used by that application even in the absence of any application specific link attributes. 8. Backward Compatibility Link attributes may be concurrently advertised in both the TE Opaque LSA [RFC3630] and the Extended Link Opaque LSA [RFC7684]. In fact, there is at least one OSPF implementation that utilizes the link attributes advertised in TE Opaque LSAs [RFC3630] for Non-RSVP 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], [I-D.ietf-rtgwg-lfa-manageability] and [I-D.psarkar-rtgwg-rlfa-node-protection]. When an OSPF routing domain includes routers using link attributes from TE Opaque LSAs for Non-RSVP TE applications such as LFA, OSPF routers in that domain should continue to advertise such TE Opaque LSAs. If there are also OSPF routers using the link attributes described herein for any application, OSPF routers in the routing domain will also need to advertise these attributes in OSPF Extended Link Attributes LSAs [RFC7684]. 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. 9. Security Considerations Implementations must assure that malformed TLV and Sub-TLV permutations do not result in errors that cause hard OSPFv2 failures. Psenak, et al. Expires February 22, 2018 [Page 11] Internet-Draft OSPFv2 Link TE Attributes Reuse August 2017 10. IANA Considerations 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: TBD1 (4 Recommended) - Remote interface IP address TBD2 (5 Recommended) - Link Local/Remote Identifiers TBD3 (6 Recommended) - Shared Risk Link Group TBD4 (7 Recommended) - Unidirectional Link Delay TBD5 (8 Recommended) - Min/Max Unidirectional Link Delay TBD6 (9 Recommended) - Unidirectional Delay Variation TBD7 (10 Recommended) - Unidirectional Link Loss TBD8 (11 Recommended) - Unidirectional Residual Bandwidth TBD9 (12 Recommended) - Unidirectional Available Bandwidth TBD10 (13 Recommended) - Unidirectional Utilized Bandwidth TBD11 (14 Recommended) - Extended Link Attribute This specification defines a new Link-Attribute-Applicability Application Bits registry and defines following bits: Bit-0 - Segment Routing Traffic Engineering Bit-1 - LFA 11. Acknowledgments Thanks to Chris Bowers for his review and comments. 12. References 12.1. 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, <https://www.rfc- editor.org/info/rfc2119>. Psenak, et al. Expires February 22, 2018 [Page 12] Internet-Draft OSPFv2 Link TE Attributes Reuse August 2017 [RFC3630] Katz, D., Kompella, K., and D. Yeung, "Traffic Engineering (TE) Extensions to OSPF Version 2", RFC 3630, DOI 10.17487/RFC3630, September 2003, <https://www.rfc- editor.org/info/rfc3630>. [RFC5714] Shand, M. and S. Bryant, "IP Fast Reroute Framework", RFC 5714, DOI 10.17487/RFC5714, January 2010, <https://www.rfc-editor.org/info/rfc5714>. [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, <https://www.rfc-editor.org/info/rfc7684>. 12.2. 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-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-18 (work in progress), July 2017. [I-D.ietf-rtgwg-lfa-manageability] Litkowski, S., Decraene, B., Filsfils, C., Raza, K., and M. Horneffer, "Operational management of Loop Free Alternates", draft-ietf-rtgwg-lfa-manageability-11 (work in progress), June 2015. [I-D.psarkar-rtgwg-rlfa-node-protection] firstname.lastname@example.org, p., Gredler, H., Hegde, S., Bowers, C., Litkowski, S., and H. Raghuveer, "Remote-LFA Node Protection and Manageability", draft-psarkar-rtgwg-rlfa- node-protection-05 (work in progress), June 2014. [RFC2328] Moy, J., "OSPF Version 2", STD 54, RFC 2328, DOI 10.17487/RFC2328, April 1998, <https://www.rfc- editor.org/info/rfc2328>. [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, <https://www.rfc-editor.org/info/rfc4203>. Psenak, et al. Expires February 22, 2018 [Page 13] Internet-Draft OSPFv2 Link TE Attributes Reuse August 2017 [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, <https://www.rfc- editor.org/info/rfc5286>. [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, <https://www.rfc-editor.org/info/rfc7471>. [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, <https://www.rfc-editor.org/info/rfc7490>. [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, <https://www.rfc-editor.org/info/rfc7855>. Authors' Addresses Peter Psenak Cisco Systems Apollo Business Center Mlynske nivy 43 Bratislava, 821 09 Slovakia Email: email@example.com Acee Lindem Cisco Systems 301 Midenhall Way Cary, NC 27513 USA Email: firstname.lastname@example.org Psenak, et al. Expires February 22, 2018 [Page 14] Internet-Draft OSPFv2 Link TE Attributes Reuse August 2017 Les Ginsberg Cisco Systems 821 Alder Drive MILPITAS, CA 95035 USA Email: email@example.com Wim Henderickx Nokia Copernicuslaan 50 Antwerp, 2018 94089 Belgium Email: firstname.lastname@example.org Jeff Tantsura Individual USA Email: email@example.com Hannes Gredler RtBrick Inc. Email: firstname.lastname@example.org Psenak, et al. Expires February 22, 2018 [Page 15]