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IDR Working Group                                   G. Van de Velde, Ed.
Internet-Draft                                             W. Henderickx
Intended status: Standards Track                                M. Bocci
Expires: September 4, 2017                                         Nokia
                                                           March 3, 2017


                      Signalling RLD using BGP-LS
           draft-vandevelde-idr-bgp-ls-segment-routing-rld-01

Abstract

   This document defines the attribute to use for BGP-LS to expose a
   node RLD "Readable Label Depth" to a centralised controller (PCE/
   SDN).

Requirements Language

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
   document are to be interpreted as described in RFC 2119 [1].

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
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   This Internet-Draft will expire on September 4, 2017.

Copyright Notice

   Copyright (c) 2017 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

   This document is subject to BCP 78 and the IETF Trust's Legal
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   (http://trustee.ietf.org/license-info) in effect on the date of
   publication of this document.  Please review these documents



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   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
   2.  Conventions used in this document . . . . . . . . . . . . . .   2
     2.1.  Terminology . . . . . . . . . . . . . . . . . . . . . . .   2
   3.  Problem Statement . . . . . . . . . . . . . . . . . . . . . .   3
   4.  RLD support by a node . . . . . . . . . . . . . . . . . . . .   3
   5.  Security Considerations . . . . . . . . . . . . . . . . . . .   4
   6.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .   4
   7.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   4
   8.  References  . . . . . . . . . . . . . . . . . . . . . . . . .   4
     8.1.  Normative References  . . . . . . . . . . . . . . . . . .   4
     8.2.  Informative References  . . . . . . . . . . . . . . . . .   4
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .   4

1.  Introduction

   When Segment Routing tunnels are computed by a centralised
   controller, it is beneficial that the controller knows the RLD
   "Readable Label Depth" of each node the computed tunnel traverses.

   RLD awareness of each node will allow the network SDN controller to
   influence the path used for each tunnel.  The SDN controller may for
   example only create tunnels with a label stack smaller or equal as
   the RLD of each node on the path.  This will allow the network to
   behave accordingly (e.g.  make use of Entropy Labels to improve ECMP)
   upon the imposed Segment Routing labels on each packet.

   This document describes how to use BGP-LS to expose the RLD of a
   node.

2.  Conventions used in this document

2.1.  Terminology

   BGP-LS: Distribution of Link-State and TE Information using Border
   Gateway Protocol

   RLD: Readable Label Depth

   PCC: Path Computation Client




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   PCE: Path Computation Element

   PCEP: Path Computation Element Protocol

   SID: Segment Identifier

   SR: Segment routing

3.  Problem Statement

   In existing technology both ISIS [4] and OSPF [3] have proposed
   extensions to signal the Readable Label Depth of a node.  However, if
   a network SDN controller is connected to the network through a BGP-LS
   session and not through ISIS or OSPF technology, then the RLD needs
   to be conveyed in BGP-LS accordingly.  This document describes the
   extension BGP-LS requires to transport the RLD.

   A network SDN controller having awareness of the Readable Label Depth
   can for example use it as a constraint on path computation so that it
   can make sure that high bandwidth LSPs are not placed on LAG links
   with smaller member bandwidths if they know the Entropy Label cannot
   be processed by the node at the ingress to the link.

4.  RLD support by a node

   Node RLD is encoded in a new Node Attribute TLV, as defined in
   RFC7752 [2].


      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            |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |     RLD       |
     +-+-+-+-+-+-+-+-+


                                 Figure 1

      Type : A 2-octet field specifying code-point of the new TLV type.
      Code-point: TBA from BGP-LS Node Descriptor, Link Descriptor,
      Prefix Descriptor, and Attribute TLVs registry

      Length: A 2-octet field that indicates the length of the value
      portion





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      RLD: Node RLD is a number in the range of 0-254.  The value of 0
      represents lack of ability to read a label stack of any depth, any
      other value represents the readable label depth of the node.

5.  Security Considerations

   This document does not introduce security issues beyond those
   discussed in RFC7752 [2]

6.  Acknowledgements

7.  IANA Considerations

   This document requests assigning 1 new code-points from the BGP-LS
   Node Descriptor, Link Descriptor, Prefix Descriptor, and Attribute
   TLVs registry as specified in sections 4.

8.  References

8.1.  Normative References

   [1]        Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119, March 1997,
              <http://xml.resource.org/public/rfc/html/rfc2119.html>.

   [2]        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,
              <http://www.rfc-editor.org/info/rfc7752>.

8.2.  Informative References

   [3]        Xu, X., Kini, S., Sivabalan, S., Filsfils, C., and S.
              Litkowski, "draft-ietf-ospf-mpls-elc", October 2016.

   [4]        Xu, X., Kini, S., Sivabalan, S., Filsfils, C., and S.
              Litkowski, "draft-ietf-ospf-mpls-elc", October 2016.

Authors' Addresses

   Gunter Van de Velde (editor)
   Nokia
   Antwerp
   BE

   Email: gunter.van_de_velde@nokia.com




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   Wim Henderickx
   Nokia
   Belgium

   Email: wim.henderickx@nokia.com


   Matthew Bocci
   Nokia
   Shoppenhangers Road
   Maidenhead, Berks
   UK

   Email: matthew.bocci@nokia.com





































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