Application-Specific Attributes Advertisement with BGP Link-State
draft-ietf-idr-bgp-ls-app-specific-attr-06

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Document Type Active Internet-Draft (idr WG)
Authors Ketan Talaulikar  , Peter Psenak  , Jeff Tantsura 
Last updated 2021-05-21 (latest revision 2021-03-08)
Replaces draft-ketant-idr-bgp-ls-app-specific-attr
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Inter-Domain Routing                                  K. Talaulikar, Ed.
Internet-Draft                                                 P. Psenak
Intended status: Standards Track                           Cisco Systems
Expires: November 22, 2021                                   J. Tantsura
                                                                  Apstra
                                                            May 21, 2021

   Application-Specific Attributes Advertisement with BGP Link-State
               draft-ietf-idr-bgp-ls-app-specific-attr-06

Abstract

   Various link attributes have been defined in link-state routing
   protocols like OSPF and IS-IS in the context of the MPLS Traffic
   Engineering (TE) and GMPLS.  BGP Link-State (BGP-LS) extensions have
   been defined to distribute these attributes along with other topology
   information from these link-state routing protocols.  Many of these
   link attributes can be used for applications other than MPLS-TE or
   GMPLS.

   Extensions to link-state routing protocols have been defined for such
   link attributes that enable distribution of their application-
   specific values.  This document defines extensions to BGP-LS address-
   family to enable advertisement of these application-specific
   attributes as a part of the topology information from the network.

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
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   Drafts is at https://datatracker.ietf.org/drafts/current/.

   Internet-Drafts are draft documents valid for a maximum of six months
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   material or to cite them other than as "work in progress."

   This Internet-Draft will expire on November 22, 2021.

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Copyright Notice

   Copyright (c) 2021 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
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   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
     1.1.  Requirements Language . . . . . . . . . . . . . . . . . .   3
   2.  Application Specific Link Attributes TLV  . . . . . . . . . .   3
   3.  Application-Specific Link Attributes  . . . . . . . . . . . .   5
   4.  Procedures  . . . . . . . . . . . . . . . . . . . . . . . . .   7
   5.  Deployment Considerations . . . . . . . . . . . . . . . . . .   9
   6.  Backward Compatibility  . . . . . . . . . . . . . . . . . . .   9
   7.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .  10
   8.  Manageability Considerations  . . . . . . . . . . . . . . . .  10
   9.  Security Considerations . . . . . . . . . . . . . . . . . . .  10
   10. Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .  11
   11. References  . . . . . . . . . . . . . . . . . . . . . . . . .  11
     11.1.  Normative References . . . . . . . . . . . . . . . . . .  11
     11.2.  Informative References . . . . . . . . . . . . . . . . .  11
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  13

1.  Introduction

   Various link attributes have been defined in link-state routing
   protocols (viz., IS-IS [RFC1195], OSPFv2 [RFC2328] and OSPFv3
   [RFC5340] ) in the context of the MPLS traffic engineering and GMPLS.
   All these attributes are distributed by these protocols using TLVs
   that were originally defined for traditional MPLS Traffic Engineering
   (i.e., using RSVP-TE [RFC3209]) or GMPLS [RFC4202] applications.

   In recent years new applications have been introduced that have use
   cases for many of the link attributes historically used by RSVP-TE
   and GMPLS.  Such applications include Segment Routing (SR) Policy
   [RFC8402] and Loop Free Alternates (LFA) [RFC5286].  This has
   introduced ambiguity in that if a deployment includes a mix of RSVP-
   TE support and SR Policy support (for example) it is not possible to

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   unambiguously indicate which advertisements are to be used by RSVP-TE
   and which advertisements are to be used by SR Policy.  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.

   [RFC8920] and [RFC8919] define extensions for OSPF and IS-IS
   respectively that address these issues.  Also, as the evolution of
   use cases for link attributes can be expected to continue in the
   years to come, these documents define an easily extensible solution
   for the introduction of new applications and new use cases.

   BGP Link-State extensions [RFC7752] have been specified to enable
   distribution of the link-state topology information from the IGPs to
   an application like a controller or Path Computation Engine (PCE) via
   BGP.  The controller/PCE gets the end-to-end topology information
   across IGP domains so it can perform path computations for use cases
   like end-to-end traffic engineering (TE) using RSVP-TE or SR Policy
   mechanisms.  A similar challenge to what was described above is hence
   also faced by such centralized computation entities.

   There is thus a need for BGP-LS extensions to also report link
   attributes on a per-application basis on the same lines as introduced
   in the link-state routing protocols.  This document defines these
   BGP-LS extensions and also covers the backward compatibility issues
   related to existing BGP-LS deployments.

1.1.  Requirements Language

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
   "OPTIONAL" in this document are to be interpreted as described in BCP
   14 [RFC2119] [RFC8174] when, and only when, they appear in all
   capitals, as shown here.

2.  Application Specific Link Attributes TLV

   The BGP-LS [RFC7752] specifies the Link NLRI for the advertisement of
   links and their attributes using the BGP-LS Attribute.  The
   Application-Specific Link Attributes (ASLA) TLV is a new optional
   top-level BGP-LS Attribute TLV that is introduced for Link NLRIs.  It
   is defined such that it may act as a container for certain existing
   and future link attributes that require application-specific
   definition.

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   The format of this TLV is as follows and is similar to the
   corresponding ASLA sub-TLVs defined for OSPF and IS-IS in [RFC8920]
   and [RFC8919] respectively.

       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            |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      | SABM Length   | UDABM Length  |            Reserved           |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |     Standard Application Identifier Bit Mask (variable)      //
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |    User-Defined Application Identifier Bit Mask (variable)   //
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                      Link Attribute sub-TLVs                 //
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

            Figure 1: Application-Specific Link Attributes TLV

   where:

   o  Type: 1122

   o  Length: variable.

   o  SABM Length : Standard Application Identifier Bit Mask Length in
      octets.  The values MUST be 0, 4, or 8.  If the Standard
      Application Identifier Bit Mask is not present, the value MUST be
      set to 0.

   o  UDABM Length : User-Defined Application Identifier Bit Mask Length
      in octets.  The values MUST be 0, 4, or 8.  If the User-Defined
      Application Identifier Bit Mask is not present, the value MUST be
      set to 0.

   o  Standard Application Identifier Bit Mask : of size 0, 4, or 8
      octets as indicated by the SABML.  Optional set of bits, where
      each bit represents a single standard application.  The bits are
      defined in the IANA "IGP Parameters" registries under the "Link
      Attribute Applications" registry [RFC8919].

   o  User-Defined Application Identifier Bit Mask : of size 0, 4, or 8
      octets as indicated by the UDABML.  Optional set of bits, where
      each bit represents a single user-defined application.  The bits
      are not managed or assigned by IANA or any other standards body
      and definition is left to the implementation.

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   o  sub-TLVs : BGP-LS Attribute TLVs corresponding to the Link NLRI
      that are application-specific (as specified in Section 3) are
      included as sub-TLVs of the ASLA TLV.

   An ASLA TLV with both the SABML and UDABML set to 0 (i.e. without any
   application identifier bit masks) indicates that the link attribute
   sub-TLVs that it encloses are applicable for all applications.

   The ASLA TLV and its sub-TLVs can only be added to the BGP-LS
   Attribute associated with the Link NLRI of the node that originates
   the underlying IGP link attribute TLVs/sub-TLVs.  The procedures for
   originating link attributes in the ASLA TLV from underlying IGPs are
   specified in Section 4.

   When the node is not running any of the IGPs but running a protocol
   like BGP, then the link attributes for the node's local links MAY be
   originated as part of the BGP-LS Attribute using the ASLA TLV and its
   sub-TLVs within the Link NLRI corresponding to the local node.

3.  Application-Specific Link Attributes

   Several BGP-LS Attribute TLVs corresponding to the Link NLRI are
   defined in BGP-LS and more may be added in the future.  The following
   types of link attributes are required to be considered application-
   specific.

   o  those that have different values for different applications (e.g.,
      a different TE metric value used for RSVP-TE than for SR Policy)

   o  those that apply to multiple applications but need to be used only
      by a specific application (e.g., certain SRLG values are
      configured on a node for LFA but the same do not need to be used
      for RSVP-TE)

   The following table lists the currently defined BGP-LS Attributes
   TLVs corresponding to Link NLRI that have application-specific
   semantics.  These were originally defined with semantics for RSVP-TE
   and GMPLS applications.

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   +-----------+---------------------+---------------------------------+
   |  TLV Code | Description         | Reference Document              |
   |   Point   |                     |                                 |
   +-----------+---------------------+---------------------------------+
   |    1088   | Administrative      | [RFC7752]                       |
   |           | group (color)       |                                 |
   |    1092   | TE Default Metric   | [RFC7752]                       |
   |    1096   | Shared Risk Link    | [RFC7752]                       |
   |           | Group               |                                 |
   |    1114   | Unidirectional Link | [RFC8571]                       |
   |           | Delay               |                                 |
   |    1115   | Min/Max             | [RFC8571]                       |
   |           | Unidirectional Link |                                 |
   |           | Delay               |                                 |
   |    1116   | Unidirectional      | [RFC8571]                       |
   |           | Delay Variation     |                                 |
   |    1117   | Unidirectional Link | [RFC8571]                       |
   |           | Loss                |                                 |
   |    1118   | Unidirectional      | [RFC8571]                       |
   |           | Residual Bandwidth  |                                 |
   |    1119   | Unidirectional      | [RFC8571]                       |
   |           | Available Bandwidth |                                 |
   |    1120   | Unidirectional      | [RFC8571]                       |
   |           | Utilized Bandwidth  |                                 |
   |    1173   | Extended            | [I-D.ietf-idr-eag-distribution] |
   |           | Administrative      |                                 |
   |           | Group               |                                 |
   +-----------+---------------------+---------------------------------+

     Table 1: BGP-LS Attribute TLVs also used as sub-TLVs of ASLA TLV

   All the BGP-LS Attribute TLVs defined in the table above are
   RECOMMENDED to continue to be advertised at the top-level in the BGP-
   LS Attribute for carrying attributes specific to RSVP-TE without the
   use of the ASLA TLV.

   When a new link attribute is introduced, it may be thought of as
   being specific to only a single application.  However, subsequently,
   it may be also shared by other applications and/or require
   application-specific values.  In such cases, it is RECOMMENDED to err
   on the side of caution and define such attributes as application-
   specific to ensure flexibility in the future.

   BGP-LS Attribute TLVs corresponding to Link NLRI that are defined in
   the future MUST specify if they are application-specific and hence
   are REQUIRED to be encoded within an ASLA TLV.

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   Only application-specific link attributes need to be advertised
   within the ASLA TLV.  Link attributes that do not have application-
   specific semantics MUST NOT be advertised within the ASLA TLV.
   Receivers MUST ignore any non-application-specific attribute sub-TLVs
   within the ASLA TLV.

   When the same application-specific link attributes are advertised
   both within the ASLA TLV and as top-level TLVs in the BGP-LS
   Attribute, the attributes advertised within the ASLA TLV take
   precedence for the applications indicated in the ASLA TLV encoding.

4.  Procedures

   The procedures described in this section apply to networks where all
   BGP-LS originators and consumers support this specification.  The
   backward compatibility aspects and operations in deployments where
   there are some BGP-LS originators or consumers that do not support
   this specification are described further in Section 6.

   The BGP-LS originator learns of the association of an application-
   specific attribute to one or more applications from either the
   underlying IGP protocol LSA/LSPs from which it is advertising the
   topology information or from the local node configuration when
   advertising attributes for the local node only.

   The association of an application-specific link attribute with a
   specific application context when advertising attributes for the
   local node only (e.g., when running BGP as the only routing protocol)
   is an implementation-specific matter and outside the scope of this
   document.

   [RFC8920] and [RFC8919] specify the mechanisms for advertising
   application-specific link attributes in OSPFv2/v3 and IS-IS
   respectively.  These IGP specifications also describe the backward
   compatibility aspects and the existing RSVP-TE/GMPLS specific TLV
   encoding mechanisms in the respective protocols.

   A BGP-LS originator node that is advertising link-state information
   from the underlying IGP determines the protocol encoding of
   application-specific link attributes based on the following rules:

   1.  Application-specific link attributes received from an IGP node
       using existing RSVP-TE/GMPLS encodings MUST be encoded using the
       respective BGP-LS top-level TLVs listed in Table 1.

   2.  Application-specific link attributes received from an IGP node
       using ASLA sub-TLV MUST be encoded in the BGP-LS ASLA TLV as sub-
       TLVs.

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   3.  In the case of IS-IS, the following specific procedures are to be
       followed:

       *  When application-specific link attributes are received from a
          node with the L bit set in the ASLA sub-TLV AND application
          bits other than RSVP-TE are set in the application bit masks
          then the application-specific link attributes advertised in
          the corresponding legacy IS-IS TLVs/sub-TLVs MUST be encoded
          within the BGP-LS ASLA TLV as sub-TLVs with the application
          bits, other than the RSVP-TE bit, copied from the IS-IS ASLA
          sub-TLV.  The link attributes advertised in the legacy IS-IS
          TLVs/sub-TLVs are also advertised in BGP-LS top-level TLVs
          listed in Table 1.  Note that this is true regardless of
          whether the RSVP-TE bit was set in the IS-IS ASLA TLV/sub-TLV.

       *  When the ASLA sub-TLV has the RSVP-TE application bit set,
          then the link attributes for the corresponding ASLA sub-TLV
          MUST be encoded using the respective BGP-LS top-level TLVs
          listed in Table 1.

       *  [RFC8919] allows the advertisement of the Maximum Link
          Bandwidth within an ASLA sub-TLV even though it is not an
          application-specific attribute.  However, when originating the
          Maximum Link Bandwidth into BGP-LS, the attribute MUST be
          encoded only in the top-level BGP-LS Maximum Link Bandwidth
          TLV (1089) and the receiver MUST ignore them when advertised
          within the BGP-LS ASLA TLV.

       *  [RFC8919] also allows the advertisement of the Maximum
          Reservable Link Bandwidth and the Unreserved Bandwidth within
          an ASLA sub-TLV even though these attributes are specific to
          RSVP-TE application.  However, when originating the Maximum
          Reservable Link Bandwidth and Unreserved Bandwidth into BGP-
          LS, these attributes MUST be encoded only in the BGP-LS top-
          level Maximum Reservable Link Bandwidth TLV (1090) and
          Unreserved Bandwidth TLV (1091) respectively and not within
          the BGP-LS ASLA TLV.

   These rules ensure that a BGP-LS originator performs the
   advertisement for all application-specific link attributes from the
   IGP nodes that support or do not support the ASLA extension.
   Furthermore, it also ensures that the top-level BGP-LS TLVs defined
   for RSVP-TE and GMPLS applications continue to be used for
   advertisement of their application-specific attributes.

   A BGP-LS consumer node would normally receive all the application-
   specific link attributes corresponding to RSVP-TE and GMPLS
   applications as existing top-level BGP-LS TLVs while for other

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   applications they are encoded in ASLA TLV(s) with appropriate
   applicable bit mask setting.  A BGP-LS consumer that implements this
   specification SHOULD prefer the application-specific attribute value
   received via sub-TLVs within the ASLA TLV over the value received via
   the top-level TLVs.

5.  Deployment Considerations

   SR Policy and LFA applications have been deployed in some networks
   using the IGP link attributes defined originally for RSVP-TE as
   discussed in [RFC8920] and [RFC8919].  The corresponding BGP-LS top-
   level link attribute TLVs originally defined for RSVP-TE have also
   been similarly used for SR Policy and LFA applications by BGP-LS
   consumers.  Such usage MAY continue without requiring the support of
   the application-specific link attribute encodings described in this
   document as long as the following conditions are met:

   o  The application is SR Policy or LFA and RSVP-TE is not deployed
      anywhere in the network

   o  The application is SR Policy or LFA, RSVP-TE is deployed in the
      network, and both the set of links on which SR Policy and/or LFA
      advertisements are required and the attribute values used by SR
      Policy and/or LFA on all such links is fully congruent with the
      links and attribute values used by RSVP-TE

6.  Backward Compatibility

   The backward compatibility aspects for BGP-LS are associated with the
   originators (i.e., nodes) and consumers (e.g., PCE, controllers,
   applications, etc.) of the topology information.  BGP-LS
   implementations have been originating link attributes and consuming
   them without any application-specific scoping prior to the extensions
   specified in this document.

   IGP backward compatibility aspects associated with application-
   specific link attributes for RSVP-TE, SR Policy, and LFA applications
   are discussed in the Backward Compatibility sections of [RFC8920] and
   [RFC8919].  While the backward compatibility aspects ensure
   compatibility of IGP advertisements, they also serve to ensure the
   backward compatibility of the BGP-LS advertisements used by BGP-LS
   consumers.  In deployments where the BGP-LS originators or consumers
   do not support the extensions specified in this document, the IGPs
   need to continue to advertise link attributes intended for use by SR
   Policy and LFA applications using the RSVP-TE/GMPLS encodings.  This
   allows BGP-LS advertisements to be consistent with the behavior prior
   to the extensions defined in this document

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   It is RECOMMENDED that nodes that support this specification are
   selected as originators of BGP-LS information when advertising the
   link-state information from the IGPs.

7.  IANA Considerations

   This document requests assignment of code-points from the registry
   "BGP-LS Node Descriptor, Link Descriptor, Prefix Descriptor, and
   Attribute TLVs" based on the table below which reflects the values
   assigned via the early allocation process.  The column "IS-IS TLV/
   Sub-TLV" defined in the registry does not require any value and
   should be left empty.

   +------------+------------------------------------------+----------+
   | Code Point |         Description                      | Length   |
   +------------+------------------------------------------+----------+
   |   1122     | Application-Specific Link Attributes TLV | variable |
   +------------+------------------------------------------+----------+

8.  Manageability Considerations

   The new protocol extensions introduced in this document augment the
   existing IGP topology information defined in [RFC7752].  Procedures
   and protocol extensions defined in this document do not affect the
   BGP protocol operations and management other than as discussed in the
   Manageability Considerations section of [RFC7752].  Specifically, the
   malformed NLRIs attribute tests in the Fault Management section of
   [RFC7752] now encompasses the BGP-LS TLVs defined in this document.

   The extensions specified in this document do not specify any new
   configuration or monitoring aspects in BGP or BGP-LS.  The
   specification of BGP models is an ongoing work based on
   [I-D.ietf-idr-bgp-model].

9.  Security Considerations

   The procedures and protocol extensions defined in this document do
   not affect the BGP security model.  See the "Security Considerations"
   section of [RFC4271] for a discussion of BGP security.  Also, refer
   to [RFC4272] and [RFC6952] for analyses of security issues for BGP.
   Security considerations for acquiring and distributing BGP-LS
   information are discussed in [RFC7752].  The TLVs introduced in this
   document are used to propagate the application-specific link
   attributes IGP extensions defined in [RFC8919] and [RFC8920].  It is
   assumed that the IGP instances originating these TLVs will support
   all the required security (as described in [RFC8919] and [RFC8920])
   in order to prevent any security issues when propagating the TLVs

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   into BGP-LS.  The advertisement of the link attribute information
   defined in this document presents no significant additional risk
   beyond that associated with the existing link attribute information
   already supported in [RFC7752].

10.  Acknowledgements

   The authors would like to thank Les Ginsberg, Baalajee S, Amalesh
   Maity, Acee Lindem, Keyur Patel and Paul Wouters for their review and
   feedback on this document.

11.  References

11.1.  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>.

   [RFC7752]  Gredler, H., Ed., Medved, J., Previdi, S., Farrel, A., and
              S. Ray, "North-Bound Distribution of Link-State and
              Traffic Engineering (TE) Information Using BGP", RFC 7752,
              DOI 10.17487/RFC7752, March 2016,
              <https://www.rfc-editor.org/info/rfc7752>.

   [RFC8174]  Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
              2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
              May 2017, <https://www.rfc-editor.org/info/rfc8174>.

   [RFC8919]  Ginsberg, L., Psenak, P., Previdi, S., Henderickx, W., and
              J. Drake, "IS-IS Application-Specific Link Attributes",
              RFC 8919, DOI 10.17487/RFC8919, October 2020,
              <https://www.rfc-editor.org/info/rfc8919>.

   [RFC8920]  Psenak, P., Ed., Ginsberg, L., Henderickx, W., Tantsura,
              J., and J. Drake, "OSPF Application-Specific Link
              Attributes", RFC 8920, DOI 10.17487/RFC8920, October 2020,
              <https://www.rfc-editor.org/info/rfc8920>.

11.2.  Informative References

   [I-D.ietf-idr-bgp-model]
              Jethanandani, M., Patel, K., Hares, S., and J. Haas, "BGP
              YANG Model for Service Provider Networks", draft-ietf-idr-
              bgp-model-10 (work in progress), November 2020.

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   [I-D.ietf-idr-eag-distribution]
              Tantsura, J., Wang, Z., Wu, Q., and K. Talaulikar,
              "Distribution of Traffic Engineering Extended
              Administrative Groups using BGP-LS", draft-ietf-idr-eag-
              distribution-16 (work in progress), April 2021.

   [RFC1195]  Callon, R., "Use of OSI IS-IS for routing in TCP/IP and
              dual environments", RFC 1195, DOI 10.17487/RFC1195,
              December 1990, <https://www.rfc-editor.org/info/rfc1195>.

   [RFC2328]  Moy, J., "OSPF Version 2", STD 54, RFC 2328,
              DOI 10.17487/RFC2328, April 1998,
              <https://www.rfc-editor.org/info/rfc2328>.

   [RFC3209]  Awduche, D., Berger, L., Gan, D., Li, T., Srinivasan, V.,
              and G. Swallow, "RSVP-TE: Extensions to RSVP for LSP
              Tunnels", RFC 3209, DOI 10.17487/RFC3209, December 2001,
              <https://www.rfc-editor.org/info/rfc3209>.

   [RFC4202]  Kompella, K., Ed. and Y. Rekhter, Ed., "Routing Extensions
              in Support of Generalized Multi-Protocol Label Switching
              (GMPLS)", RFC 4202, DOI 10.17487/RFC4202, October 2005,
              <https://www.rfc-editor.org/info/rfc4202>.

   [RFC4271]  Rekhter, Y., Ed., Li, T., Ed., and S. Hares, Ed., "A
              Border Gateway Protocol 4 (BGP-4)", RFC 4271,
              DOI 10.17487/RFC4271, January 2006,
              <https://www.rfc-editor.org/info/rfc4271>.

   [RFC4272]  Murphy, S., "BGP Security Vulnerabilities Analysis",
              RFC 4272, DOI 10.17487/RFC4272, January 2006,
              <https://www.rfc-editor.org/info/rfc4272>.

   [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>.

   [RFC5340]  Coltun, R., Ferguson, D., Moy, J., and A. Lindem, "OSPF
              for IPv6", RFC 5340, DOI 10.17487/RFC5340, July 2008,
              <https://www.rfc-editor.org/info/rfc5340>.

   [RFC6952]  Jethanandani, M., Patel, K., and L. Zheng, "Analysis of
              BGP, LDP, PCEP, and MSDP Issues According to the Keying
              and Authentication for Routing Protocols (KARP) Design
              Guide", RFC 6952, DOI 10.17487/RFC6952, May 2013,
              <https://www.rfc-editor.org/info/rfc6952>.

Talaulikar, et al.      Expires November 22, 2021              [Page 12]
Internet-Draft  BGP-LS Extns for App Specific Attributes        May 2021

   [RFC8402]  Filsfils, C., Ed., Previdi, S., Ed., Ginsberg, L.,
              Decraene, B., Litkowski, S., and R. Shakir, "Segment
              Routing Architecture", RFC 8402, DOI 10.17487/RFC8402,
              July 2018, <https://www.rfc-editor.org/info/rfc8402>.

   [RFC8571]  Ginsberg, L., Ed., Previdi, S., Wu, Q., Tantsura, J., and
              C. Filsfils, "BGP - Link State (BGP-LS) Advertisement of
              IGP Traffic Engineering Performance Metric Extensions",
              RFC 8571, DOI 10.17487/RFC8571, March 2019,
              <https://www.rfc-editor.org/info/rfc8571>.

Authors' Addresses

   Ketan Talaulikar (editor)
   Cisco Systems
   India

   Email: ketant@cisco.com

   Peter Psenak
   Cisco Systems
   Slovakia

   Email: ppsenak@cisco.com

   Jeff Tantsura
   Apstra

   Email: jefftant.ietf@gmail.com

Talaulikar, et al.      Expires November 22, 2021              [Page 13]