Skip to main content

HyStart++: Modified Slow Start for TCP
RFC 9406

Approval announcement
Draft of message to be sent after approval:


From: The IESG <>
To: IETF-Announce <>
Cc: The IESG <>,,,,,,
Subject: Protocol Action: 'HyStart++: Modified Slow Start for TCP' to Proposed Standard (draft-ietf-tcpm-hystartplusplus-14.txt)

The IESG has approved the following document:
- 'HyStart++: Modified Slow Start for TCP'
  (draft-ietf-tcpm-hystartplusplus-14.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 Martin Duke.

A URL of this Internet-Draft is:

Ballot Text

Technical Summary

   This document describes HyStart++, a simple modification to the slow start phase of congestion control algorithms. Traditional slow start can overshoot the ideal send rate in many cases, causing high packet loss and poor performance. HyStart++ uses a delay increase heuristic to find an exit point before possible overshoot. It also adds a mitigation to prevent jitter from causing premature slow start exit.

Working Group Summary

The document has broad agreement, in particular from TCP implementers. There was no controversy.

Document Quality

   There are implementations for the TCP stacks in FreeBSD, Linux, and Windows,
   and a QUIC implementations Quiche from CloudFlare and s2n-quic from AWS.?


The document shepherd is Michael Tuexen. The AD is Martin Duke.

RFC Editor Note