I-D ACTION:draft-ietf-pilc-asym-08.txt

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This draft is a work item of the Performance Implications of Link Characteristics Working Group of the IETF.

	Title		: TCP Performance Implications of Network Path Asymmetry
	Author(s)	: H. Balakrishnan, V. Padmanabhan et al.
	Filename	: draft-ietf-pilc-asym-08.txt
	Pages		: 37
	Date		: 2002-10-2
	
This document describes TCP performance problems that arise because 
of asymmetric effects. These problems arise in several access 
networks, including bandwidth-asymmetric networks and packet radio 
subnetworks, for different underlying reasons. However, the end 
result on TCP performance is the same in both cases: performance 
often degrades significantly because of imperfection and variability 
in the ACK feedback from the receiver to the sender.  
The document details several mitigations to these effects, which 
have either been proposed or evaluated in the literature, or are 
currently deployed in networks.  These solutions use a combination 
of local link-layer techniques, subnetwork, and end-to-end 
mechanisms, consisting of: (i) techniques to manage the channel used 
for the upstream bottleneck link carrying the ACKs, typically using 
header compression or reducing the frequency of TCP ACKs,  (ii) 
techniques to handle this reduced ACK frequency to retain the TCP 
sender's acknowledgment-triggered self-clocking and (iii) techniques 
to schedule the data and ACK packets in the reverse direction to 
improve performance in the presence of two-way traffic. Each 
technique is described, together with known issues, and 
recommendations for use. A summary of the recommendations is 
provided at the end of the document.

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