Congestion Exposure (ConEx) Concepts and Abstract Mechanism
draft-ietf-conex-abstract-mech-04
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Congestion Exposure (ConEx) Working M. Mathis
Group Google, Inc
Internet-Draft B. Briscoe
Intended status: Informational BT
Expires: September 13, 2012 March 12, 2012
Congestion Exposure (ConEx) Concepts and Abstract Mechanism
draft-ietf-conex-abstract-mech-04
Abstract
This document describes an abstract mechanism by which senders inform
the network about the congestion encountered by packets earlier in
the same flow. Today, network elements at any layer may signal
congestion to the receiver by dropping packets or by ECN markings,
and the receiver passes this information back to the sender in
transport-layer feedback. The mechanism described here enables the
sender to also relay this congestion information back into the
network in-band at the IP layer, such that the total amount of
congestion from all elements on the path is revealed to all IP
elements along the path, where it could, for example, be used to
provide input to traffic management. This mechanism is called
congestion exposure or ConEx. The companion document "ConEx Concepts
and Use Cases" provides the entry-point to the set of ConEx
documentation.
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
Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet-
Drafts is at http://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress."
This Internet-Draft will expire on September 13, 2012.
Copyright Notice
Copyright (c) 2012 IETF Trust and the persons identified as the
document authors. All rights reserved.
Mathis & Briscoe Expires September 13, 2012 [Page 1]
Internet-Draft ConEx Concepts and Abstract Mechanism March 2012
This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents
(http://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents
carefully, as they describe your rights and restrictions with respect
to this document. Code Components extracted from this document must
include Simplified BSD License text as described in Section 4.e of
the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
1.1. Terminology . . . . . . . . . . . . . . . . . . . . . . . 7
2. Requirements for the ConEx Abstract Mechanism . . . . . . . . 7
2.1. Requirements for ConEx Signals . . . . . . . . . . . . . . 7
2.2. Requirements for the Audit Function . . . . . . . . . . . 8
2.3. Requirements for non-abstract ConEx specifications . . . . 9
3. Encoding Congestion Exposure . . . . . . . . . . . . . . . . . 10
3.1. Naive Encoding . . . . . . . . . . . . . . . . . . . . . . 10
3.2. Null Encoding . . . . . . . . . . . . . . . . . . . . . . 11
3.3. ECN Based Encoding . . . . . . . . . . . . . . . . . . . . 11
3.4. Independent Bits . . . . . . . . . . . . . . . . . . . . . 12
3.5. Codepoint Encoding . . . . . . . . . . . . . . . . . . . . 12
3.6. Units Implied by an Encoding . . . . . . . . . . . . . . . 13
4. Congestion Exposure Components . . . . . . . . . . . . . . . . 15
4.1. Network Devices (Not modified) . . . . . . . . . . . . . . 15
4.2. Modified Senders . . . . . . . . . . . . . . . . . . . . . 15
4.3. Receivers (Optionally Modified) . . . . . . . . . . . . . 15
4.4. Policy Devices . . . . . . . . . . . . . . . . . . . . . . 16
4.4.1. Congestion Monitoring Devices . . . . . . . . . . . . 16
4.4.2. Rest-of-Path Congestion Monitoring . . . . . . . . . . 16
4.4.3. Congestion Policers . . . . . . . . . . . . . . . . . 17
4.5. Audit . . . . . . . . . . . . . . . . . . . . . . . . . . 17
4.5.1. Using Credit to Simplify Audit . . . . . . . . . . . . 20
5. Support for Incremental Deployment . . . . . . . . . . . . . . 20
6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 22
7. Security Considerations . . . . . . . . . . . . . . . . . . . 23
8. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 23
9. Comments Solicited . . . . . . . . . . . . . . . . . . . . . . 23
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