Overview of Pre-Congestion Notification Encoding
RFC 6627
Document | Type | RFC - Informational (July 2012; No errata) | |
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Authors | Georgios Karagiannis , Kwok Chan , Toby Moncaster , Michael Menth , Philip Eardley , Bob Briscoe | ||
Last updated | 2018-12-20 | ||
Replaces | draft-chan-pcn-encoding-comparison | ||
Stream | Internent Engineering Task Force (IETF) | ||
Formats | plain text html pdf htmlized (tools) htmlized bibtex | ||
Reviews | |||
Stream | WG state | WG Document | |
Document shepherd | Steven Blake | ||
Shepherd write-up | Show (last changed 2011-07-02) | ||
IESG | IESG state | RFC 6627 (Informational) | |
Action Holders |
(None)
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Consensus Boilerplate | Unknown | ||
Telechat date | |||
Responsible AD | Martin Stiemerling | ||
IESG note | Steven Blake, PCN co-chair (slblake@petri-meat.com) is the document shepherd. | ||
Send notices to | (None) |
Internet Engineering Task Force (IETF) G. Karagiannis Request for Comments: 6627 University of Twente Category: Informational K. Chan ISSN: 2070-1721 Consultant T. Moncaster University of Cambridge M. Menth University of Tuebingen P. Eardley B. Briscoe BT July 2012 Overview of Pre-Congestion Notification Encoding Abstract The objective of Pre-Congestion Notification (PCN) is to protect the quality of service (QoS) of inelastic flows within a Diffserv domain. On every link in the PCN-domain, the overall rate of PCN-traffic is metered, and PCN-packets are appropriately marked when certain configured rates are exceeded. Egress nodes provide decision points with information about the PCN-marks of PCN-packets that allows them to take decisions about whether to admit or block a new flow request, and to terminate some already admitted flows during serious pre-congestion. The PCN working group explored a number of approaches for encoding this pre-congestion information into the IP header. This document provides details of those approaches along with an explanation of the constraints that apply to any solution. 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/rfc6627. Karagiannis, et al. Informational [Page 1] RFC 6627 Pre-Congestion Notification Encoding July 2012 Copyright Notice Copyright (c) 2012 IETF Trust and the persons identified as the document authors. All rights reserved. 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. Karagiannis, et al. Informational [Page 2] RFC 6627 Pre-Congestion Notification Encoding July 2012 Table of Contents 1. Introduction ....................................................4 2. General PCN Encoding Requirements ...............................5 2.1. Metering and Marking Algorithms ............................5 2.2. Approaches for PCN-Based Admission Control and Flow Termination ................................................5 2.2.1. Dual Marking (DM) ...................................5 2.2.2. Single Marking (SM) .................................6 2.2.3. Packet-Specific Dual Marking (PSDM) .................7 2.2.4. Preferential Packet Dropping ........................8 3. Encoding Constraints ............................................9 3.1. Structure of the DS Field ..................................9 3.2. Constraints from the DS Field ..............................9 3.2.1. General Scarcity of DSCPs ...........................9 3.2.2. Handling of the DSCP in Tunneling Rules ............10 3.2.3. Restoration of Original DSCPs at the Egress Node ...10 3.3. Constraints from the ECN Field ............................11 3.3.1. Structure and Use of the ECN Field .................11 3.3.2. Redefinition of the ECN Field ......................12 3.3.3. Handling of the ECN Field in Tunneling Rules .......12 3.3.3.1. Limited-Functionality Option ..............12 3.3.3.2. Full-Functionality Option .................13Show full document text