Internet Engineering Task Force (IETF) B. Briscoe, Ed.
Request for Comments: 6789 BT
Category: Informational R. Woundy, Ed.
ISSN: 2070-1721 Comcast
A. Cooper, Ed.
CDT
December 2012
Congestion Exposure (ConEx) Concepts and Use Cases
Abstract
This document provides the entry point to the set of documentation
about the Congestion Exposure (ConEx) protocol. It explains the
motivation for including a ConEx marking at the IP layer: to expose
information about congestion to network nodes. Although such
information may have a number of uses, this document focuses on how
the information communicated by the ConEx marking can serve as the
basis for significantly more efficient and effective traffic
management than what exists on the Internet today.
Status of This Memo
This document is not an Internet Standards Track specification; it is
published for informational purposes.
This document is a product of the Internet Engineering Task Force
(IETF). It represents the consensus of the IETF community. It has
received public review and has been approved for publication by the
Internet Engineering Steering Group (IESG). Not all documents
approved by the IESG are a candidate for any level of Internet
Standard; see Section 2 of RFC 5741.
Information about the current status of this document, any errata,
and how to provide feedback on it may be obtained at
http://www.rfc-editor.org/info/rfc6789.
Briscoe, et al. Informational [Page 1]RFC 6789 ConEx Concepts and Use Cases December 2012Copyright Notice
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Concepts . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
2.1. Congestion . . . . . . . . . . . . . . . . . . . . . . . . 5
2.2. Congestion-Volume . . . . . . . . . . . . . . . . . . . . 5
2.3. Rest-of-Path Congestion . . . . . . . . . . . . . . . . . 6
2.4. Definitions . . . . . . . . . . . . . . . . . . . . . . . 6
3. Core Use Case: Informing Traffic Management . . . . . . . . . 7
3.1. Use Case Description . . . . . . . . . . . . . . . . . . . 7
3.2. Additional Benefits . . . . . . . . . . . . . . . . . . . 9
3.3. Comparison with Existing Approaches . . . . . . . . . . . 9
4. Other Use Cases . . . . . . . . . . . . . . . . . . . . . . . 11
5. Deployment Arrangements . . . . . . . . . . . . . . . . . . . 12
6. Experimental Considerations . . . . . . . . . . . . . . . . . 13
7. Security Considerations . . . . . . . . . . . . . . . . . . . 14
8. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 14
9. Contributors . . . . . . . . . . . . . . . . . . . . . . . . . 15
10. Informative References . . . . . . . . . . . . . . . . . . . . 15
1. Introduction
The power of Internet technology comes from multiplexing shared
capacity with packets rather than circuits. Network operators aim to
provide sufficient shared capacity, but when too much packet load
meets too little shared capacity, congestion results. Congestion
appears as either increased delay, dropped packets, or packets
explicitly marked with Explicit Congestion Notification (ECN)
markings [RFC3168]. As described in Figure 1, congestion control
currently relies on the transport receiver detecting these
'Congestion Signals' and informing the transport sender in
'Congestion Feedback Signals'. The sender is then expected to reduce
its rate in response.
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