TRILL (TRansparent Interconnection of Lots of Links): ECN (Explicit Congestion Notification) Support
draft-ietf-trill-ecn-support-07

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TRILL Working Group                                      Donald Eastlake
INTERNET-DRAFT                                                    Huawei
Intended status: Proposed Standard                           Bob Briscoe
                                                               CableLabs
Expires: August 24, 2018                               February 25, 2018

         TRILL (TRansparent Interconnection of Lots of Links):
             ECN (Explicit Congestion Notification) Support
                 <draft-ietf-trill-ecn-support-07.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 congestion control without packet drops.
   This document extends ECN to TRILL (TRansparent Interconnection of
   Lots of Links) 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
      3.3.1 Non-ECN Egress RBridges..............................8
      3.3.2 ECN Egress RBridges..................................8

      4. TRILL Support for ECN Variants.........................11
      4.1 Pre-Congestion Notification (PCN).....................11
      4.2 Low Latency, Low Loss, Scalable Throughput (L4S)......12

      5. IANA Considerations....................................13
      6. Security Considerations................................14

      7. Acknowledgements.......................................14

      Normative References......................................15
      Informative References....................................16

      Appendix A. TRILL Transit RBridge Behavior to Support L4S.17

      Authors' Addresses........................................19

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

1. Introduction

   Explicit congestion notification (ECN [RFC3168] [RFC8311]) 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
   congestion 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|