TRILL: ECN (Explicit Congestion Notification) Support
draft-ietf-trill-ecn-support-03

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Last updated 2017-05-31 (latest revision 2017-05-28)
Replaces draft-eastlake-trill-ecn-support
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TRILL Working Group                                      Donald Eastlake
INTERNET-DRAFT                                                    Huawei
Intended status: Proposed Standard                           Bob Briscoe
                                                     Simula Research Lab
Expires: November 27, 2017                                  May 28, 2017

         TRILL: ECN (Explicit Congestion Notification) Support
                 <draft-ietf-trill-ecn-support-03.txt>

Abstract

   Explicit congestion notification (ECN) allows a forwarding element to
   notify downstream devices, including the destination, of the onset of
   congestion without having to drop packets. This can improve network
   efficiency through better flow control without packet drops. This
   document extends ECN to TRILL switches, including integration with IP
   ECN, and provides for ECN marking in the TRILL Header Extension Flags
   Word (see RFC 7179).

Status of This Memo

   This Internet-Draft is submitted to IETF in full conformance with the
   provisions of BCP 78 and BCP 79.

   Distribution of this document is unlimited. Comments should be sent
   to the TRILL working group mailing list <trill@ietf.org>.

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D. Eastlake & B.Briscoe                                         [Page 1]
INTERNET-DRAFT                                         TRILL ECN Support

Table of Contents

      1. Introduction............................................3
      1.1 Conventions used in this document......................4

      2. The ECN Specific Extended Header Flags..................6

      3. ECN Support.............................................7
      3.1 Ingress ECN Support....................................7
      3.2 Transit ECN Support....................................7
      3.3 Egress ECN Support.....................................8

      4. TRILL Support for ECN Variants.........................10
      4.1 Pre-Congestion Notification (PCN).....................10
      4.2 Low Latency, Low Loss, Scalable Throughput (L4S)......11

      5. IANA Considerations....................................12
      6. Security Considerations................................13
      7. Acknowledgements.......................................13

      Normative References......................................14
      Informative References....................................15

      Appendix A. TRILL Transit RBridge Behavior to Support L4S.16

      Authors' Addresses........................................18

D. Eastlake & B.Briscoe                                         [Page 2]
INTERNET-DRAFT                                         TRILL ECN Support

1. Introduction

   Explicit congestion notification (ECN [RFC3168]) allows a forwarding
   element, such as a router, to notify downstream devices, including
   the destination, of the onset of congestion without having to drop
   packets. This can improve network efficiency through better flow
   control without packet drops. The forwarding element can explicitly
   mark a proportion of packets in an ECN field instead of dropping the
   packet. For example, a two-bit field is available for ECN marking in
   IP headers.

                     .............................
                     .                           .
                 +---------+                     .
    +------+     | Ingress |                     .
    |Source|  +->| RBridge |                     .   +----------+
    +---+--+  |  |   RB1   |                     .   |Forwarding|
        |     |  +------+--+  +----------+       .   | Element  |
        v     |      .  |     | Transit  |       .   |    Y     |
      +-------+--+   .  +---->| RBridges |       .   +--------+-+
      |Forwarding|   .        |   RBn    |       .      ^     |
      | Element  |   .        +-------+--+  +---------+ |     v
      |    X     |   .                |     | Egress  | |  +-----------+
      +----------+   .                +---->| RBridge +-+  |Destination|
                     .                      |   RB9   |    +-----------+
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