Encoding Three Pre-Congestion Notification (PCN) States in the IP Header Using a Single Diffserv Codepoint (DSCP)
RFC 6660
| Document | Type |
RFC - Proposed Standard
(July 2012; No errata)
Obsoletes RFC 5696
|
|
|---|---|---|---|
| Last updated | 2018-12-20 | ||
| Replaces | draft-briscoe-pcn-3-in-1-encoding | ||
| Stream | IETF | ||
| Formats | plain text html pdf htmlized bibtex | ||
| Reviews | |||
| Stream | WG state | WG Document | |
| Document shepherd | No shepherd assigned | ||
| IESG | IESG state | RFC 6660 (Proposed Standard) | |
| Consensus Boilerplate | Unknown | ||
| Telechat date | |||
| Responsible AD | Martin Stiemerling | ||
| IESG note | Scott Bradner (sob@harvard.edu) is the document shephed. | ||
| Send notices to | (None) | ||
Internet Engineering Task Force (IETF) B. Briscoe
Request for Comments: 6660 BT
Obsoletes: 5696 T. Moncaster
Category: Standards Track University of Cambridge
ISSN: 2070-1721 M. Menth
University of Tuebingen
July 2012
Encoding Three Pre-Congestion Notification (PCN) States
in the IP Header Using a Single Diffserv Codepoint (DSCP)
Abstract
The objective of Pre-Congestion Notification (PCN) is to protect the
quality of service (QoS) of inelastic flows within a Diffserv domain.
The overall rate of PCN-traffic is metered on every link in the PCN-
domain, and PCN-packets are appropriately marked when certain
configured rates are exceeded. Egress nodes pass information about
these PCN-marks to Decision Points that then decide whether to admit
or block new flow requests or to terminate some already admitted
flows during serious pre-congestion.
This document specifies how PCN-marks are to be encoded into the IP
header by reusing the Explicit Congestion Notification (ECN)
codepoints within a PCN-domain. The PCN wire protocol for non-IP
protocol headers will need to be defined elsewhere. Nonetheless,
this document clarifies the PCN encoding for MPLS in an informational
appendix. The encoding for IP provides for up to three different PCN
marking states using a single Diffserv codepoint (DSCP): not-marked
(NM), threshold-marked (ThM), and excess-traffic-marked (ETM).
Hence, it is called the 3-in-1 PCN encoding. This document obsoletes
RFC 5696.
Status of This Memo
This is an Internet Standards Track document.
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). Further information on
Internet Standards is available in 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/rfc6660.
Briscoe, et al. Standards Track [Page 1]
RFC 6660 3-in-1 PCN Encoding July 2012
Copyright Notice
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
1.1. Requirements Language . . . . . . . . . . . . . . . . . . 4
2. Definitions and Abbreviations . . . . . . . . . . . . . . . . 4
2.1. Terminology . . . . . . . . . . . . . . . . . . . . . . . 4
2.2. List of Abbreviations . . . . . . . . . . . . . . . . . . 5
3. Definition of 3-in-1 PCN Encoding . . . . . . . . . . . . . . 6
4. Requirements for and Applicability of 3-in-1 PCN Encoding . . 7
4.1. PCN Requirements . . . . . . . . . . . . . . . . . . . . . 7
4.2. Requirements Imposed by Tunnelling . . . . . . . . . . . . 7
4.3. Applicable Environments for the 3-in-1 PCN Encoding . . . 8
5. Behaviour of a PCN-node to Comply with the 3-in-1 PCN
Encoding . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
5.1. PCN-Ingress-Node Behaviour . . . . . . . . . . . . . . . . 8
5.2. PCN-Interior-Node Behaviour . . . . . . . . . . . . . . . 11
5.2.1. Behaviour Common to All PCN-Interior-Nodes . . . . . . 11
5.2.2. Behaviour of PCN-Interior-Nodes Using Two
PCN-Markings . . . . . . . . . . . . . . . . . . . . . 11
5.2.3. Behaviour of PCN-Interior-Nodes Using One
PCN-Marking . . . . . . . . . . . . . . . . . . . . . 12
5.3. PCN-Egress-Node Behaviour . . . . . . . . . . . . . . . . 13
6. Backward Compatibility . . . . . . . . . . . . . . . . . . . . 13
6.1. Backward Compatibility with ECN . . . . . . . . . . . . . 13
6.2. Backward Compatibility with the Encoding in RFC 5696 . . . 14
7. Security Considerations . . . . . . . . . . . . . . . . . . . 14
8. Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . 15
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