BGP Extension for SR-MPLS Entropy Label Position
draft-zhou-idr-bgp-srmpls-elp-00

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IDR Working Group                                                J. Zhou
Internet-Draft                                              Shaofu. Peng
Intended status: Standards Track                               ZTE Corp.
Expires: August 21, 2020                                    Feb 18, 2020

            BGP Extension for SR-MPLS Entropy Label Position
                    draft-zhou-idr-bgp-srmpls-elp-00

Abstract

   This document proposed an extension for BGP to configure the entropy
   label position for SR-MPLS networks.

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   This Internet-Draft will expire on August 21, 2020.

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Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  BGP Extensions of Segment Flags . . . . . . . . . . . . . . .   2
   3.  Operations  . . . . . . . . . . . . . . . . . . . . . . . . .   3
   4.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   3
   5.  Normative References  . . . . . . . . . . . . . . . . . . . .   3
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .   3

1.  Introduction

   Entropy Label(EL)[RFC6790] is a technology that can be used for load-
   balancing in Segment Routing (SR) MPLS.
   [I-D.ietf-mpls-spring-entropy-label] discusses in detail the factors
   to be considered when inserting EL in SR, analyzes the possible
   insertion positions of entropy labels, and gives a specific algorithm
   for calculating the position of entropy labels.

   An MPLS label stack can contain multiple ELs, so multiple EL
   insertion positions may be calculated.  When calculating the
   position, it is necessary to consider the Maximum SID Depth(MSD)
   capability of the head node and Entropy Readable Label Depth(ERLD)
   capability of the intermediate node in combination with the
   algorithm.  The position calculation of EL is usually completed by
   the controller, which is issued by the controller to the head node.

   [I-D.ietf-idr-segment-routing-te-policy] defines the specific process
   of how the controller in the SR network passes the path calculation
   result of the SR-TE policy to the head node of the network through
   BGP.

   In this document, the EL position information is transmitted by
   extending the flags of Segment List Sub-TLV in the BGP.

2.  BGP Extensions of Segment Flags

   The Segment Flags is defined in Section 2.4.3.2.12 of
   [I-D.ietf-idr-segment-routing-te-policy].

       0 1 2 3 4 5 6 7
      +-+-+-+-+-+-+-+-+
      |V|A|E|          |
      +-+-+-+-+-+-+-+-+

   E-Flag: This flag indicates that presence of <ELI, EL> label pairs
   are inserted after this segment.  It is applicable to all Segment
   Types.

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3.  Operations

   Supposed the head end had received a SR-TE path from the controller
   with multiple Segment List Sub-TLVs, for example, <S1, S2, S3, S4,
   S5, S6>, especially S3 and S6 with E-flag.  It indicates that two
   <ELI, EL> pairs SHOULD be inserted into the label stack of the SR-TE
   forwarding entry, respectively after the Label for S3 and Label for
   S6.  With EL information, the label stack for SR-MPLS would be
   <label1, label2, label3, ELI, EL, label4, label5, label6, ELI, EL>.

4.  IANA Considerations

   This document requests bit 2 for Entropy Label Flag.

    Bit     Description                                Reference
   ------------------------------------------------------------------
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