Tree Engineering for Bit Index Explicit Replication (BIER-TE)
draft-ietf-bier-te-arch-08
Network Working Group T. Eckert, Ed.
Internet-Draft Futurewei
Intended status: Standards Track G. Cauchie
Expires: January 14, 2021 Bouygues Telecom
M. Menth
University of Tuebingen
July 13, 2020
Tree Engineering for Bit Index Explicit Replication (BIER-TE)
draft-ietf-bier-te-arch-08
Abstract
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.
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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
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Internet-Drafts are draft documents valid for a maximum of six months
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material or to cite them other than as "work in progress."
This Internet-Draft will expire on January 14, 2021.
Eckert, et al. Expires January 14, 2021 [Page 2]
Internet-Draft BIER-TE ARCH July 2020
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