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