More Accurate Explicit Congestion Notification (AccECN) Feedback in TCP
draft-ietf-tcpm-accurate-ecn-34

Approval announcement
Draft of message to be sent after approval:

Announcement

From: The IESG <iesg-secretary@ietf.org>
To: IETF-Announce <ietf-announce@ietf.org>
Cc: The IESG <iesg@ietf.org>, draft-ietf-tcpm-accurate-ecn@ietf.org, rfc-editor@rfc-editor.org, tcpm-chairs@ietf.org, tcpm@ietf.org, tuexen@fh-muenster.de, zahed.sarker.ietf@gmail.com
Subject: Protocol Action: 'More Accurate Explicit Congestion Notification (AccECN) Feedback in TCP' to Proposed Standard (draft-ietf-tcpm-accurate-ecn-34.txt)

The IESG has approved the following document:
- 'More Accurate Explicit Congestion Notification (AccECN) Feedback in
   TCP'
  (draft-ietf-tcpm-accurate-ecn-34.txt) as Proposed Standard

This document is the product of the TCP Maintenance and Minor Extensions
Working Group.

The IESG contact persons are Zaheduzzaman Sarker and Francesca Palombini.

A URL of this Internet-Draft is:
https://datatracker.ietf.org/doc/draft-ietf-tcpm-accurate-ecn/

Ballot Text

Technical Summary

   Explicit Congestion Notification (ECN) is a mechanism where network
   nodes can mark IP packets instead of dropping them to indicate
   incipient congestion to the endpoints.  Receivers with an ECN-capable
   transport protocol feed back this information to the sender.  ECN was
   originally specified for TCP in such a way that only one feedback
   signal can be transmitted per Round-Trip Time (RTT).  Recent new TCP
   mechanisms like Congestion Exposure (ConEx), Data Center TCP (DCTCP)
   or Low Latency, Low Loss, and Scalable Throughput (L4S) need more
   accurate ECN feedback information whenever more than one marking is
   received in one RTT.  This document updates the original ECN
   specification in RFC 3168 to specify a scheme that provides more than
   one feedback signal per RTT in the TCP header.  Given TCP header
   space is scarce, it allocates a reserved header bit previously
   assigned to the ECN-Nonce.  It also overloads the two existing ECN
   flags in the TCP header.  The resulting extra space is exploited to
   feed back the IP-ECN field received during the 3-way handshake as
   well.  Supplementary feedback information can optionally be provided
   in two new TCP option alternatives, which are never used on the TCP
   SYN.  The document also specifies the treatment of this updated TCP
   wire protocol by middleboxes.

Working Group Summary

   There is strong consensus in the WG, except for one individual (see the shepherd's writeup).

Document Quality

   Apple has an implementation in its latest released version of their
     operating systems. Disabled by default.
   * There is an implementation for FreeBSD, which will be committed to the
     source tree, as soon as the document is finished.
   * There is also an implementation for Linux where people are working on getting
     it into the main tree.
   * Tooling support is also there. Wireshark support is there and also support
     in packetdrill.
   All this support was possible, since the TCP option kind numbers where early
   assigned.

Personnel

   The Document Shepherd for this document is Michael Tüxen. The
   Responsible Area Director is Zaheduzzaman Sarker.

RFC Editor Note