Signalling ERLD using BGP-LS
draft-ietf-idr-bgp-ls-segment-routing-rld-05

Document Type Active Internet-Draft (idr WG)
Last updated 2019-08-20
Replaces draft-vandevelde-idr-bgp-ls-segment-routing-rld
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IDR Working Group                                   G. Van de Velde, Ed.
Internet-Draft                                             W. Henderickx
Intended status: Standards Track                                M. Bocci
Expires: February 21, 2020                                         Nokia
                                                                K. Patel
                                                                  Arrcus
                                                         August 20, 2019

                      Signalling ERLD using BGP-LS
              draft-ietf-idr-bgp-ls-segment-routing-rld-05

Abstract

   This document defines the attribute encoding to use for BGP-LS to
   expose ERLD "Entropy capable Readable Label Depth" from a node 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 February 21, 2020.

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

Van de Velde, et al.    Expires February 21, 2020               [Page 1]
Internet-Draft        Signalling ERLD using BGP-LS           August 2019

   (https://trustee.ietf.org/license-info) in effect on the date of
   publication of this document.  Please review these documents
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   described in the Simplified BSD License.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Conventions used in this document . . . . . . . . . . . . . .   2
     2.1.  Terminology . . . . . . . . . . . . . . . . . . . . . . .   3
   3.  Problem Statement . . . . . . . . . . . . . . . . . . . . . .   3
   4.  Advertising of ERLD in BGP-LS . . . . . . . . . . . . . . . .   3
   5.  Security Considerations . . . . . . . . . . . . . . . . . . .   4
   6.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .   4
   7.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   4
   8.  References  . . . . . . . . . . . . . . . . . . . . . . . . .   4
     8.1.  Normative References  . . . . . . . . . . . . . . . . . .   4
     8.2.  Informative References  . . . . . . . . . . . . . . . . .   5
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .   5

1.  Introduction

   When Segment Routing tunnels are computed by a centralised
   controller, it is beneficial that the controller knows the ERLD
   (Entropy Readable Label Depth) of each node or link a tunnel
   traverses.  A network node signalling an ERLD MUST support the
   ability to read the signalled number of labels before any action is
   done upon the packet and SHOULD support entropy awareness found
   within the signalled ERLD depth.

   ERLD awareness of each node will allow a 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 ERLD 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 label stack on each packet.

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

2.  Conventions used in this document

Van de Velde, et al.    Expires February 21, 2020               [Page 2]
Internet-Draft        Signalling ERLD using BGP-LS           August 2019

2.1.  Terminology

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

   ERLD: Entropy capable Readable Label Depth

   ELC: Entropy Label Capability

   MSD: Maximum SID Depth

   SID: Segment Identifier

3.  Problem Statement

   For Segment Routing technology both ISIS [7] and OSPF [6] have
   proposed extensions to signal the ERLD (Entropy Readable Label Depth)
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