Increasing TCP's Initial Window
RFC 6928

Approval announcement
Draft of message to be sent after approval:

From: The IESG <>
To: IETF-Announce <>
Cc: RFC Editor <>,
    tcpm mailing list <>,
    tcpm chair <>
Subject: Document Action: 'Increasing TCP's Initial Window' to Experimental RFC (draft-ietf-tcpm-initcwnd-08.txt)

The IESG has approved the following document:
- 'Increasing TCP's Initial Window'
  (draft-ietf-tcpm-initcwnd-08.txt) as Experimental RFC

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

The IESG contact persons are Wesley Eddy and Martin Stiemerling.

A URL of this Internet Draft is:

Technical Summary:

  This document describes an experimental proposal to increase initial congestion window
  of TCP to at most 10 segments as well as a fall-back mechanism to limit any negative
  effects in limited buffer or bandwidth situations.
  It also provides guidelines to enable/disable this features in addition to some metrics
  to monitor the effect of this.

Working Group Summary:

  There has been dominant opinions in the WG to increase initial window size of TCP.
  Question was whether we have a single updated value, or increasing the value gradually
  with a certain schedule, or defining a mechanics to adjust initial window size over time.
  We have explored several possibilities and eventually having a single updated value
  has become the consensus of the WG as other methods have some difficulties for
  large-scale deployment. Some of the approach in other methods have been merged into the
  draft during this process. The consensus was clear as no opinion against this proposal
  has been raised since then.

Document Quality:

  Linux has already incorporated this proposal in the main kernel distribution.
  This document was reviewed by various people and has been discussed in the WG for
  nearly three years. The authors have provided results from their extensive experiments
  with a larger initial window. They also provided data to address questions and concerns
  by reviewers. In addition, there have been some related experiments by other TCPM contributors,
  mostly based on simulation. The document has been updated based on feedback from the community.

  I believe the authors did fairly extensive work for an experimental RFC, even if valid questions
  are still to be answered. The remaining questions, which need further experiments, are hard
  to address by the authors alone. Appendix A in the document contains the list for major
  discussion points of the draft.


  Yoshifumi Nishida is the Document Shepherd for this document.
  The Responsible Area Director is Wesley Eddy.

RFC Editor Note

At the end of the 4th paragraph in section 12, please append:

It is recognized that if IW10 is causing harm to other traffic, that this may not
be readily apparent to the the software on the hosts using IW10.  In some
cases a local system or network administrator may be able to detect this,
and to selectively disable IW10 in such cases.  In the general case, however,
since the harm may occur on a remote network, to other cross-traffic,
there may be no good way at all for this to be detected or corrected.  Current
experience and analysis does not indicate whether this is a real issue, beyond
a hypothetical one.  As use of IW10 becomes more prevalent, monitoring and
analysis of flows throughout the network will be needed to assess the impact
across the spectrum of scenarios found on the real Internet.