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Using TCP Selective Acknowledgement (SACK) Information to Determine Duplicate Acknowledgements for Loss Recovery Initiation

Document Type Expired Internet-Draft (tcpm WG)
Expired & archived
Authors Ilpo Järvinen , Markku Kojo
Last updated 2023-06-26 (Latest revision 2010-03-08)
Replaces draft-jarvinen-tcpm-sack-recovery-entry
RFC stream Internet Engineering Task Force (IETF)
Intended RFC status (None)
Additional resources Mailing list discussion
Stream WG state Dead WG Document
Document shepherd (None)
IESG IESG state Expired
Consensus boilerplate Unknown
Telechat date (None)
Responsible AD (None)
Send notices to (None)

This Internet-Draft is no longer active. A copy of the expired Internet-Draft is available in these formats:


This document describes a TCP sender algorithm to trigger loss recovery based on the TCP Selective Acknowledgement (SACK) information gathered on a SACK scoreboard instead of simply counting the number of arriving duplicate acknowledgements (ACKs) in the traditional way. The given algorithm is more robust to ACK losses, ACK reordering, missed duplicate acknowledgements due to delayed acknowledgements, and extra duplicate acknowledgements due to duplicated segments and out-of-window segments. The algorithm allows not only a timely initiation of TCP loss recovery but also reduces false fast retransmits. It has a low implementation cost on top of the SACK scoreboard defined in RFC 3517.


Ilpo Järvinen
Markku Kojo

(Note: The e-mail addresses provided for the authors of this Internet-Draft may no longer be valid.)