The Addition of Explicit Congestion Notification (ECN) to IP
RFC 3168
| Document | Type |
RFC - Proposed Standard
(September 2001; Errata)
Obsoletes RFC 2481
Was draft-ietf-tsvwg-ecn (tsvwg WG)
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|---|---|---|---|
| Last updated | 2013-03-02 | ||
| Stream | IETF | ||
| Formats | plain text pdf html bibtex | ||
| Stream | WG state | (None) | |
| Document shepherd | No shepherd assigned | ||
| IESG | IESG state | RFC 3168 (Proposed Standard) | |
| Consensus Boilerplate | Unknown | ||
| Telechat date | |||
| Responsible AD | (None) | ||
| Send notices to | (None) | ||
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.......... 32
9.2.1.2. ECN Tunnel Security Association Attribute............... 32
9.2.1.3. Changes to IPsec Tunnel Header Processing............... 33
9.2.2. Changes to the ECN Field within an IPsec Tunnel........... 35
9.2.3. Comments for IPsec Support................................ 35
9.3. IP packets encapsulated in non-IP Packet Headers............ 36
10. Issues Raised by Monitoring and Policing Devices............. 36
11. Evaluations of ECN........................................... 37
11.1. Related Work Evaluating ECN................................ 37
11.2. A Discussion of the ECN nonce.............................. 37
11.2.1. The Incremental Deployment of ECT(1) in Routers.......... 38
12. Summary of changes required in IP and TCP.................... 38
13. Conclusions.................................................. 40
14. Acknowledgements............................................. 41
15. References................................................... 41
16. Security Considerations...................................... 45
17. IPv4 Header Checksum Recalculation........................... 45
18. Possible Changes to the ECN Field in the Network............. 45
18.1. Possible Changes to the IP Header.......................... 46
18.1.1. Erasing the Congestion Indication........................ 46
18.1.2. Falsely Reporting Congestion............................. 47
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