Application Specific Attributes Advertisement with BGP Link-State
draft-ietf-idr-bgp-ls-app-specific-attr-00

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Inter-Domain Routing                                       K. Talaulikar
Internet-Draft                                                 P. Psenak
Intended status: Standards Track                           Cisco Systems
Expires: December 1, 2019                                    J. Tantsura
                                                                  Apstra
                                                            May 30, 2019

   Application Specific Attributes Advertisement with BGP Link-State
               draft-ietf-idr-bgp-ls-app-specific-attr-00

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 which 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.

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.

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

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   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 December 1, 2019.

Copyright Notice

   Copyright (c) 2019 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

   This document is subject to BCP 78 and the IETF Trust's Legal
   Provisions Relating to IETF Documents
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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
   2.  Application Specific Link Attributes TLV  . . . . . . . . . .   3
   3.  Application Specific Link Attributes  . . . . . . . . . . . .   5
   4.  Procedures  . . . . . . . . . . . . . . . . . . . . . . . . .   7
   5.  Backward Compatibility  . . . . . . . . . . . . . . . . . . .   8
   6.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .  10
   7.  Manageability Considerations  . . . . . . . . . . . . . . . .  10
     7.1.  Operational Considerations  . . . . . . . . . . . . . . .  10
     7.2.  Management Considerations . . . . . . . . . . . . . . . .  10
   8.  Security Considerations . . . . . . . . . . . . . . . . . . .  10
   9.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .  11
   10. References  . . . . . . . . . . . . . . . . . . . . . . . . .  11
     10.1.  Normative References . . . . . . . . . . . . . . . . . .  11
     10.2.  Informative References . . . . . . . . . . . . . . . . .  11
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  12

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.

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   In recent years new applications have been introduced which have use
   cases for many of the link attributes historically used by RSVP-TE
   and GMPLS.  Such applications include Segment Routing (SR) [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 support (for example) it is not possible to unambiguously
   indicate which advertisements are to be used by RSVP-TE and which
   advertisements are to be used by SR.  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.  IGP Flexible Algorithm
   [I-D.ietf-lsr-flex-algo] is one such application use-case that MAY
   use application specific link attributes.

   [I-D.ietf-ospf-te-link-attr-reuse] and [I-D.ietf-isis-te-app] define
   extensions for OSPF and IS-IS respectively which address these
   issues.  Also, as evolution of use cases for link attributes can be
   expected to continue in the years to come, these documents define a
   solution which is easily extensible to 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 based
   mechanisms.  A similar challenge to what was describe 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.

2.  Application Specific Link Attributes TLV

   The BGP-LS [RFC7752] specifies the Link NLRI for 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 to be defined in an
   application specific scope.

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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
   [I-D.ietf-ospf-te-link-attr-reuse] and [I-D.ietf-isis-te-app]
   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            |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |     SABML     |     UDABML    |            Reserved           |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |        Standard Application Bit-Mask (variable)              //
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |       User Defined Application Bit-Mask (variable)           //
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                      Link Attribute sub-TLVs                 //
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

            Figure 1: Application Specific Link Attributes TLV

   where:

   o  Type: TBD (see IANA Considerations Section 6)

   o  Length: variable.

   o  SABML : 1 octet value carrying the Standard Application Bit-Mask
      Length in multiples of 4 octets.  If the Standard Application Bit-
      Mask is not present, the SABML MUST be set to 0.

   o  UDABML : 1 octet value carrying the User Defined Application Bit-
      Mask Length in multiples of 4 octets.  If the User Defined
      Application Bit-Mask is not present, the UDABML MUST be set to 0.

   o  Standard Application Bit-Mask : variable size in multiple of 4
      octets and 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 [I-D.ietf-isis-te-app].

   o  User Defined Application Bit-Mask : variable size in multiple of 4
      octets and 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 are left to
      implementation specifics.

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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 specific bitmasks) indicate 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 is
   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 as 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 TE)

   o  those that are applicable to multiple applications but need to be
      used only by 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 which have application specific
   semantics.  They were originally defined with semantics for RSVP-TE
   and GMPLS applications.

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   +----------+----------------------+---------------------------------+
   | TLV Code | Description          | Reference Document              |
   |  Point   |                      |                                 |
   +----------+----------------------+---------------------------------+
   |   1088   | Administrative group | [RFC7752]                       |
   |          | (color)              |                                 |
   |   1090   | Max Reservable       | [RFC7752]                       |
   |          | Bandwidth            |                                 |
   |   1091   | Unreserved Bandwidth | [RFC7752]                       |
   |   1092   | TE Metric            | [RFC7752]                       |
   |   1096   | SRLG                 | [RFC7752]                       |
   |   1114   | Unidirectional link  | [I-D.ietf-idr-te-pm-bgp]        |
   |          | delay                |                                 |
   |   1115   | Min/Max              | [I-D.ietf-idr-te-pm-bgp]        |
   |          | Unidirectional link  |                                 |
   |          | delay                |                                 |
   |   1116   | Unidirectional link  | [I-D.ietf-idr-te-pm-bgp]        |
   |          | delay variation      |                                 |
   |   1117   | Unidirectional       | [I-D.ietf-idr-te-pm-bgp]        |
   |          | packet loss          |                                 |
   |   1118   | Unidirectional       | [I-D.ietf-idr-te-pm-bgp]        |
   |          | residual bandwidth   |                                 |
   |   1119   | Unidirectional       | [I-D.ietf-idr-te-pm-bgp]        |
   |          | available bandwidth  |                                 |
   |   1120   | Unidirectional       | [I-D.ietf-idr-te-pm-bgp]        |
   |          | bandwidth            |                                 |
   |          | utilization          |                                 |
   |   1173   | Extended             | [I-D.ietf-idr-eag-distribution] |
   |          | Administrative group |                                 |
   |          | (color)              |                                 |
   +----------+----------------------+---------------------------------+

     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 be continued to be used at the top-level in the BGP-LS
   Attribute for carrying attributes specific to RSVP-TE/GMPLS
   application 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, down the line,
   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.

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   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.

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

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 is described further in Section 5.

   The BGP-LS originator learns of the association of an application
   specific attribute to one or more set of applications from either the
   underlying IGP protocol LSA/LSPs from which it is sourcing 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.

   [I-D.ietf-ospf-te-link-attr-reuse] and [I-D.ietf-isis-te-app] specify
   the mechanisms for flooding of 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 respective protocols.

   A BGP-LS originator node which is sourcing link-state information
   from the underlying IGP determines the mechanism of flooding
   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 only (i.e. without any
       ASLA sub-TLV) MUST be encoded using the respective BGP-LS top-
       level TLVs listed in Table 1 (i.e. not within ASLA TLV).  When
       the IGP node is also SR enabled then another copy of application
       specific link attributes SHOULD be also encoded as ASLA sub-TLVs
       with the SR application bit for them.  Further rules do not apply

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       for such IGP nodes that do not use ASLA sub-TLVs in their
       advertisements.

   2.  In case of IS-IS, when application specific link attributes are
       received from a node with the L bit set in the ASLA sub-TLV then
       the application specific link attributes are picked up from the
       legacy ISIS TLVs/sub-TLVs and MUST be encoded within the BGP-LS
       ASLA TLV as sub-TLVs with the application bitmask set as per the
       IGP ASLA sub-TLV.  When the ASLA sub-TLV with the L bit set also
       has the RSVP-TE application bit set then the link attributes from
       such an ASLA sub-TLV MUST be also encoded using the respective
       BGP-LS top-level TLVs listed in Table 1 (i.e. not within ASLA
       TLV).

   3.  In case of OSPFv2/v3, when application specific link attributes
       are received from a node via TE LSAs then the application
       specific link attributes from those LSAs MUST be encoded using
       the respective BGP-LS TLVs listed in Table 1 (i.e. not within
       ASLA TLV).

   4.  Application specific link attributes received from an IGP node
       within its ASLA sub-TLV MUST be encoded in the BGP-LS ASLA TLV as
       sub-TLVs with the application bitmask set as per the IGP
       advertisement.

   These rules ensure that a BGP-LS originator performs the translation
   for all application specific link attributes from the IGP nodes into
   the new BGP-LS ASLA TLVs irrespective of the IGP node supporting the
   ASLA extension.  Furthermore, it also ensures that BGP-LS TLVs
   defined for RSVP-TE and GMPLS applications continue to be used for
   those respective applications.

   A BGP-LS consumer node always gets all application specific link
   attributes corresponding to RSVP-TE and GMPLS applications as
   existing top-level BGP-LS TLVs while for other applications they are
   encoded in ASLA TLV(s) with appropriate applicable bit mask setting.

5.  Backward Compatibility

   When it comes to BGP-LS, the backward compatibility aspects are
   associated with the originators (i.e. nodes) and consumers (e.g.
   PCE, controllers, applications, etc.) of the topology information.
   The originators of BGP-LS information need to ensure that their
   encoding of application specific link attributes is done such that
   consumers running BGP-LS implementations without this specification
   support can still support existing applications like RSVP-TE and SR.
   The consumers running BGP-LS implementations that support this

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   specification should also be able to work with BGP-LS originators
   that do not support this specification and vice versa.

   BGP-LS implementations have been originating link attributes and
   consuming them without any application specific scoping.  While the
   ASLA TLV can be used without any backward compatibility
   considerations for any new application (e.g.  IGP Flexible Algorithm)
   specific attribute advertisements, for existing applications like
   RSVP-TE and SR some backward compatibility aspects need to be taken
   care of.

   This requires the introduction of a "compatibility mode" of
   operations at originators of BGP-LS information for encoding of
   information such that older implementations of BGP-LS consumers can
   still support applications like RSVP-TE and SR.  In addition to the
   rules specified in Section 4, the following rules are to be followed
   when operating in "compatibility mode" :

   o  Application specific link attribute received in IGP ASLA sub-TLVs,
      corresponding to RSVP-TE or SR applications, MUST be also encoded
      in their existing top level TLVs (as listed in Table 1) outside of
      the ASLA TLV in addition to them being also advertised within the
      ASLA TLV

   o  When the same application specific attribute, received in IGP ASLA
      sub-TLVs, has different values for RSVP-TE and SR applications
      then the value for RSVP-TE application SHOULD be preferred over
      the value for SR application for advertisement as the top level
      TLV (as listed in Table 1).  An implementation MAY provide a knob
      to reverse this preference.

   It is RECOMMENDED that implementations operate in "compatibility
   mode" by default.  Implementations SHOULD have a knob for turning the
   "compatibility mode" on or off.  Operators MAY turn the
   "compatibility mode" off when they are assured that all BGP-LS
   consumers have been upgraded to support the extensions in this
   document.

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

   A BGP-LS consumer which does not implement this specification will
   ignore the ASLA TLV and instead continue to use the attributes from
   the existing top level TLVs.

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   A BGP-LS consumer which 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.

6.  IANA Considerations

   This document requests assigning code-points from the registry "BGP-
   LS Node Descriptor, Link Descriptor, Prefix Descriptor, and Attribute
   TLVs" based on table below.  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   |
   +------------+------------------------------------------+----------+
   |    TBD     | Application Specific Link Attributes TLV | variable |
   +------------+------------------------------------------+----------+

7.  Manageability Considerations

   This section is structured as recommended in [RFC5706].

   The new protocol extensions introduced in this document augment the
   existing IGP topology information that was distributed via [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 encompass the new TLVs for the
   BGP-LS NLRI in this document.

7.1.  Operational Considerations

   No additional operation considerations are defined in this document.

7.2.  Management Considerations

   No additional management considerations are defined in this document.

8.  Security Considerations

   The new protocol extensions introduced in this document augment the
   existing IGP topology information that was distributed via [RFC7752].
   Procedures and protocol extensions defined in this document do not
   affect the BGP security model other than as discussed in the Security
   Considerations section of [RFC7752].

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9.  Acknowledgements

   The authors would like to thank Les Ginsberg for his review and
   contributions to this work.

10.  References

10.1.  Normative References

   [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-06 (work in progress), April 2019.

   [I-D.ietf-ospf-te-link-attr-reuse]
              Psenak, P., Ginsberg, L., Henderickx, W., Tantsura, J.,
              and J. Drake, "OSPF Link Traffic Engineering (TE)
              Attribute Reuse", draft-ietf-ospf-te-link-attr-reuse-07
              (work in progress), April 2019.

   [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>.

10.2.  Informative References

   [I-D.ietf-idr-eag-distribution]
              Wang, Z., Wu, Q., and J. Tantsura, "Distribution of MPLS-
              TE Extended admin Group Using BGP", draft-ietf-idr-eag-
              distribution-08 (work in progress), October 2018.

   [I-D.ietf-idr-te-pm-bgp]
              Ginsberg, L., Previdi, S., Wu, Q., Tantsura, J., and C.
              Filsfils, "BGP-LS Advertisement of IGP Traffic Engineering
              Performance Metric Extensions", draft-ietf-idr-te-pm-
              bgp-18 (work in progress), December 2018.

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   [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-02 (work in progress), May 2019.

   [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>.

   [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>.

   [RFC5706]  Harrington, D., "Guidelines for Considering Operations and
              Management of New Protocols and Protocol Extensions",
              RFC 5706, DOI 10.17487/RFC5706, November 2009,
              <https://www.rfc-editor.org/info/rfc5706>.

   [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>.

Authors' Addresses

   Ketan Talaulikar
   Cisco Systems

   Email: ketant@cisco.com

Talaulikar, et al.      Expires December 1, 2019               [Page 12]
Internet-Draft  BGP-LS Extns for App Specific Attributes        May 2019

   Peter Psenak
   Cisco Systems
   Slovakia

   Email: ppsenak@cisco.com

   Jeff Tantsura
   Apstra

   Email: jefftant.ietf@gmail.com

Talaulikar, et al.      Expires December 1, 2019               [Page 13]