The RACK-TLP Loss Detection Algorithm for TCP
RFC 8985

Approval announcement
Draft of message to be sent after approval:

From: The IESG <>
To: IETF-Announce <>
Cc: The IESG <>,,,,,,,
Subject: Protocol Action: 'The RACK-TLP loss detection algorithm for TCP' to Proposed Standard (draft-ietf-tcpm-rack-15.txt)

The IESG has approved the following document:
- 'The RACK-TLP loss detection algorithm for TCP'
  (draft-ietf-tcpm-rack-15.txt) as Proposed Standard

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

The IESG contact persons are Martin Duke and Magnus Westerlund.

A URL of this Internet Draft is:

Technical Summary

   This document presents the RACK-TLP loss detection algorithm for TCP.
   RACK-TLP uses per-segment transmit timestamps and selective
   acknowledgements (SACK) and has two parts: RACK ("Recent
   ACKnowledgment") starts fast recovery quickly using time-based
   inferences derived from ACK feedback.  TLP ("Tail Loss Probe")
   leverages RACK and sends a probe packet to trigger ACK feedback to
   avoid retransmission timeout (RTO) events.  Compared to the widely
   used DUPACK threshold approach, RACK-TLP detects losses more
   efficiently when there are application-limited flights of data, lost
   retransmissions, or data packet reordering events.  It is intended to
   be an alternative to the DUPACK threshold approach.

Working Group Summary

  The general approach was uncontroversial. As the algorithm is quite
  intricate, there were many comments to clarify the text and the

Document Quality

The core mechanisms described in the document are implemented in FreeBSD, Linux, and Windows. They are in active use on these platforms. RACK can also be used by other transport protocols. QUIC loss recovery uses the same ideas and there exists also an implementation for SCTP within a simulation environment.


   The document shepherd is Michael Tüxen. The Responsible AD is Martin Duke