RFC 3042 (rfc3042) - Page 1 of 9
Enhancing TCP's Loss Recovery Using Limited Transmit
Alternative Format: Original Text Document
Network Working Group M. Allman
Request for Comments: 3042 NASA GRC/BBN
Category: Standards Track H. Balakrishnan
MIT
S. Floyd
ACIRI
January 2001
Enhancing TCP's Loss Recovery Using Limited Transmit
Status of this Memo
This document specifies an Internet standards track protocol for the
Internet community, and requests discussion and suggestions for
improvements. Please refer to the current edition of the "Internet
Official Protocol Standards" (STD 1) for the standardization state
and status of this protocol. Distribution of this memo is unlimited.
Copyright Notice
Copyright (C) The Internet Society (2001). All Rights Reserved.
Abstract
This document proposes a new Transmission Control Protocol (TCP)
mechanism that can be used to more effectively recover lost segments
when a connection's congestion window is small, or when a large
number of segments are lost in a single transmission window. The
"Limited Transmit" algorithm calls for sending a new data segment in
response to each of the first two duplicate acknowledgments that
arrive at the sender. Transmitting these segments increases the
probability that TCP can recover from a single lost segment using the
fast retransmit algorithm, rather than using a costly retransmission
timeout. Limited Transmit can be used both in conjunction with, and
in the absence of, the TCP selective acknowledgment (SACK) mechanism.
1 Introduction
A number of researchers have observed that TCP's loss recovery
strategies do not work well when the congestion window at a TCP
sender is small. This can happen, for instance, because there is
only a limited amount of data to send, or because of the limit
imposed by the receiver-advertised window, or because of the
constraints imposed by end-to-end congestion control over a
connection with a small bandwidth-delay product
[Riz96,Mor97,BPS+98,Bal98,LK98]. When a TCP detects a missing
segment, it enters a loss recovery phase using one of two methods.
Allman, et al. Standards Track