Subject: I-D ACTION:draft-floyd-sack-00.txt

From: [email-masked]
Date: Tue, 31 Aug 1999 07:06:20 -0400

A New Internet-Draft is available from the on-line Internet-Drafts directories.

	Title		: An Extension to the Selective Acknowledgement (SACK) 
                          Option for TCP
	Author(s)	: S. Floyd, J. Mahdavi, M. Mathis, M. Podolsky,
                          A. Romanow
	Filename	: draft-floyd-sack-00.txt
	Pages		: 14
	Date		: 30-Aug-99
	
This note defines an extension of the Selective Acknowledgement
(SACK) Option [RFC2018] for TCP.  RFC 2018 specified the use of the
SACK option for acknowledging out-of-sequence data not covered by
TCP's cumulative acknowledgement field.  This note extends RFC 2018
by specifying the use of the SACK option for acknowledging duplicate
packets.  This note suggests that when duplicate packets are
received, the first block of the SACK option field can be used to
report the sequence numbers of the packet that triggered the
acknowledgement.  This extension to the SACK option allows the TCP
sender to infer the order of packets received at the receiver,
allowing the sender to infer when it has unnecessarily retransmitted
a packet.  A TCP sender could then use this information for more
robust operation in an environment of reordered packets, ACK loss,
packet replication, and/or early retransmit timeouts.

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