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The Addition of Explicit Congestion Notification (ECN) to IP (RFC3168)

IP.com Disclosure Number: IPCOM000005398D
Original Publication Date: 2001-Sep-01
Included in the Prior Art Database: 2001-Sep-21

Publishing Venue

Internet Society Requests For Comment (RFCs)

Related People

K. Ramakrishnan: AUTHOR [+3]

Abstract

This memo specifies the incorporation of ECN (Explicit Congestion Notification) to TCP and IP, including ECN's use of two bits in the IP header.

This text was extracted from a ASCII document.
This is the abbreviated version, containing approximately 2% of the total text.

Network Working Group K. Ramakrishnan Request for Comments: 3168 TeraOptic Networks Updates: 2474, 2401, 793 S. Floyd Obsoletes: 2481 ACIRI Category: Standards Track D. Black

EMC September 2001

The Addition of Explicit Congestion Notification (ECN) to IP

Status of this Memo

This document specifies an Internet standards track protocol for the Internet community, and requests discussion and suggestions for improvements. Please refer to the current edition of the "Internet Official Protocol Standards" (STD 1) for the standardization state and status of this protocol. Distribution of this memo is unlimited.

Copyright Notice

Copyright (C) The Internet Society (2001). All Rights Reserved.

Abstract

This memo specifies the incorporation of ECN (Explicit Congestion Notification) to TCP and IP, including ECN's use of two bits in the IP header.

Table of Contents

1. Introduction.................................................. 3 2. Conventions and Acronyms...................................... 5 3. Assumptions and General Principles............................ 5 4. Active Queue Management (AQM)................................. 6 5. Explicit Congestion Notification in IP........................ 6 5.1. ECN as an Indication of Persistent Congestion............... 10 5.2. Dropped or Corrupted Packets................................ 11 5.3. Fragmentation............................................... 11 6. Support from the Transport Protocol........................... 12 6.1. TCP......................................................... 13 6.1.1 TCP Initialization......................................... 14 6.1.1.1. Middlebox Issues........................................ 16 6.1.1.2. Robust TCP Initialization with an Echoed Reserved Field. 17 6.1.2. The TCP Sender............................................ 18 6.1.3. The TCP Receiver.......................................... 19 6.1.4. Congestion on the ACK-path................................ 20 6.1.5. Retransmitted TCP packets................................. 20

Ramakrishnan, et al. Standards Track [Page 1]

RFC 3168 The Addition of ECN to IP September 2001

6.1.6. TCP Window Probes......................................... 22 7. Non-compliance by the End Nodes............................... 22 8. Non-compliance in the Network................................. 24 8.1. Complications Introduced by Split Paths..................... 25 9. Encapsulated Packets.......................................... 25 9.1. IP packets encapsulated in IP............................... 25 9.1.1. The Limited-functionality and Full-functionality Options.. 27 9.1.2. Changes to the ECN Field within an IP Tunnel.............. 28 9.2. IPsec Tunnels............................................... 29 9.2.1. Negotiation between Tunnel Endpoints...................... 31 9.2.1.1. ECN Tunnel Security Association Database Field............