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

Document Type Expired Internet-Draft (tcpm WG)
Authors Ilpo Järvinen  , Markku Kojo 
Last updated 2010-03-08
Replaces draft-jarvinen-tcpm-sack-recovery-entry
Stream Internet Engineering Task Force (IETF)
Intended RFC status (None)
Expired & archived
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Stream WG state WG Document
Document shepherd No shepherd assigned
IESG IESG state Expired
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This Internet-Draft is no longer active. A copy of the expired Internet-Draft can be found at


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.)