Single-path PREF
draft-huang-detnet-single-path-pref-00

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DetNet                                                          D. Huang
Internet-Draft                                                       ZTE
Intended status: Standards Track                       December 13, 2017
Expires: June 16, 2018

                            Single-path PREF
                 draft-huang-detnet-single-path-pref-00

Abstract

   This document specifies PREF on the single path for low-rate traffic,
   and illustrates in details the implementation solutions as well as
   the impacts on the data plane specified in [I-D.ietf-detnet-dp-alt].

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Huang                     Expires June 16, 2018                 [Page 1]
Internet-Draft              Single-path PREF               December 2017

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Convention used in this document  . . . . . . . . . . . . . .   3
   3.  Terminology and definitions . . . . . . . . . . . . . . . . .   3
   4.  Encapsulation impacts . . . . . . . . . . . . . . . . . . . .   3
     4.1.  Flow ID/Label . . . . . . . . . . . . . . . . . . . . . .   3
     4.2.  Control word  . . . . . . . . . . . . . . . . . . . . . .   4
   5.  Replication solutions . . . . . . . . . . . . . . . . . . . .   4
     5.1.  Discontinuous traffic . . . . . . . . . . . . . . . . . .   5
     5.2.  Continuous traffic  . . . . . . . . . . . . . . . . . . .   5
   6.  Forwarder clarifications  . . . . . . . . . . . . . . . . . .   5
     6.1.  Edge node clarifications  . . . . . . . . . . . . . . . .   5
     6.2.  Relay node clarification  . . . . . . . . . . . . . . . .   5
   7.  Traffic rate limit  . . . . . . . . . . . . . . . . . . . . .   6
   8.  Normative References  . . . . . . . . . . . . . . . . . . . .   6
   Author's Address  . . . . . . . . . . . . . . . . . . . . . . . .   6

1.  Introduction

   PREF is designed to protect the Detnet traffic against path or node
   failures in [I-D.ietf-detnet-architecture] by directing multiple
   copies of the traffic into multiple paths.  Lost packets would be
   recovered at the converging node (or terminating node) from the
   undamaged traffic in other path.  Nevertheless, path and node failure
   always result in disastrous consequences for the ongoing service,
   large blocks of data loss or even total service breakdown, while PREF
   with multiple paths protection would also provide good cross-check
   for the minor packet loss which guarantees the data integrity as well
   as latency benefits (retransmission reduced significantly).  When it
   comes to the latter scenario, PREF on the single path will do the
   better job particularly for the low-rate traffic.

   Packet replication is executed in edge node, what's significantly
   different from the multi-path PREF is the copies would be arranged in
   the same traffic flow rather than delivering along different paths,
   either transport or forwarding nodes do not have to execute PREF
   which should only be done at the terminating node.  The rationale is
   that if packet loss occurs at any intermediary nodes, the multiple
   packet copies could execute cross-checking and rebuild the damaged
   data flow, and make the usual retransmission unnecessary to a large
   degree.  Two major benefits follow, intermediary network nodes do not
   need support PREF, and if the node is a PREF node, it does not
   execute PREF.  Secondly, no or reduced buffer reservation should be
   required in the nodes along the routing path.

   Multiple copies in the same data traffic put bandwidth pressure upon
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