Tree Engineering for Bit Index Explicit Replication (BIER-TE)

Document Type Active Internet-Draft (bier WG)
Authors Toerless Eckert  , Gregory Cauchie  , Michael Menth 
Last updated 2020-12-10 (latest revision 2020-10-30)
Replaces draft-eckert-bier-te-arch
Stream IETF
Intended RFC status Proposed Standard
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Stream WG state Submitted to IESG for Publication
Document shepherd Xuesong Geng
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IESG IESG state Publication Requested
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Network Working Group                                     T. Eckert, Ed.
Internet-Draft                                                 Futurewei
Intended status: Standards Track                              G. Cauchie
Expires: May 3, 2021                                    Bouygues Telecom
                                                                M. Menth
                                                 University of Tuebingen
                                                            Oct 30, 2020

     Tree Engineering for Bit Index Explicit Replication (BIER-TE)


   This memo introduces per-packet stateless strict and loose path
   steered replication and forwarding for Bit Index Explicit Replication
   packets (RFC8279).  This is called BIER Tree Engineering (BIER-TE).
   BIER-TE can be used as a path steering mechanism in future Traffic
   Engineering solutions for BIER (BIER-TE).

   BIER-TE leverages RFC8279 and extends it with a new semantic for bits
   in the bitstring.  BIER-TE can leverage BIER forwarding engines with
   little or no changes.

   In BIER, the BitPositions (BP) of the packets bitstring indicate BIER
   Forwarding Egress Routers (BFER), and hop-by-hop forwarding uses a
   Routing Underlay such as an IGP.

   In BIER-TE, BitPositions indicate adjacencies.  The BIFT of each BFR
   are only populated with BPs that are adjacent to the BFR in the BIER-
   TE topology.  The BIER-TE topology can consist of layer 2 or remote
   (routed) adjacencies.  The BFR then replicates and forwards BIER
   packets to those adjacencies.  This results in the aforementioned
   strict and loose path steering and replications.

   BIER-TE can co-exist with BIER forwarding in the same domain, for
   example by using separate BIER sub-domains.  In the absence of routed
   adjacencies, BIER-TE does not require a BIER routing underlay, and
   can then be operated without requiring an Interior Gateway Routing
   protocol (IGP).

   BIER-TE operates without explicit in-network tree-state and carries
   the multicast distribution tree in the packet header.  It can
   therefore be a good fit to support multicast path steering in Segment
   Routing (SR) networks.

Eckert, et al.             Expires May 3, 2021                  [Page 1]
Internet-Draft                BIER-TE ARCH                      Oct 2020

Name explanation

   [RFC-editor: This section to be removed before publication.]

   Explanation for name change from BIER-TE to mean "Traffic
   Engineering" to BIER-TE "Tree Engineering" in WG last-call (to
   benefit IETF/IESG reviewers):

   This document started by calling itself BIER-TE, "Traffic
   Engineering" as it is a mode of BIER specifically beneficial for
   Traffic Engineering.  It supports per-packet bitstring based policy
   steering and replication.  BIER-TE technology itself does not provide
   a complete traffic engineering solution for BIER but would require
   combination with other technologies for a full BIER based TE
   solution, such as a PCE and queuing mechanisms to provide bandwidth
   and latency reservations.  It is also not the only option to build a
   traffic engineering solution utilizing BIER, for example BIER trees
   could be steered through IGP metric engineering, such as through
   Flex-Topologies.  The architecure for Traffic Engineering with either
   modes of BIER (BIER-TE/BIER) is intended to be defined in a separate
   document, most likely in TEAs WG.

   Because the name of such an overall solution is intended to be BIER-
   TE, the expansion of BIER-TE was therefore changed to name this BIER
   mode "Tree Engineering", so the overall solution can be distinguished
   better from its tree building/engineering method without having to
   change the long time well-established abbreviation BIER-TE.

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

   Internet-Drafts are draft documents valid for a maximum of six months
   and may be updated, replaced, or obsoleted by other documents at any
   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 May 3, 2021.

Eckert, et al.             Expires May 3, 2021                  [Page 2]
Internet-Draft                BIER-TE ARCH                      Oct 2020

Copyright Notice

   Copyright (c) 2020 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
   ( in effect on the date of
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