Return-Path: <majordom@ISI.EDU>
Received: from RI.CMU.EDU by n1.sp.cs.cmu.edu id aa31077; 11 Aug 97 16:54 EDT
Received: from zephyr.isi.edu by RI.CMU.EDU id aa19405; 11 Aug 97 16:54:02 EDT
Received: by zephyr.isi.edu (5.65c/5.61+local-26)
	id <AA07935>; Mon, 11 Aug 1997 13:41:23 -0700
Received: from tnt.isi.edu by zephyr.isi.edu (5.65c/5.61+local-26)
	id <AA07929>; Mon, 11 Aug 1997 13:41:21 -0700
Received: from desolation.CS.Berkeley.EDU (desolation.CS.Berkeley.EDU [128.32.33.142])
	by tnt.isi.edu (8.8.7/8.8.6) with ESMTP id NAA06125
	for <end2end-interest@isi.edu>; Mon, 11 Aug 1997 13:41:20 -0700 (PDT)
Received: from desolation.CS.Berkeley.EDU (padmanab@localhost) by desolation.CS.Berkeley.EDU (8.8.3/8.8.2) with ESMTP id NAA27239 for <end2end-interest@isi.edu>; Mon, 11 Aug 1997 13:38:47 -0700 (PDT)
Message-Id: <199708112038.NAA27239@desolation.CS.Berkeley.EDU>
X-Mailer: exmh version 1.6.9 8/22/96
Reply-To: Venkat Padmanabhan <padmanab@cs.berkeley.edu>
From: Venkat Padmanabhan <padmanab@cs.berkeley.edu>
To: end2end-interest@ISI.EDU
Subject: Mobicom '97 paper on TCP over asymmetric networks
X-Face: 8oz'i+bl`|5PbRnbf:lhb^%e[KkX6s2O+~WXUjjyZy3<eONU1x6ko7NU'ZWaahSA9@z67tI
 imt6ht.__nYj:ufI1]z(DMC4k*hEJO=Y3iihd[[ZDHRV<%<Gl,tJqvQ`2h*[FyU&7F=>Ew*s3R1@]D
 {~a]r4V]),Mlwru>UYa+!f7aeLD3),v{_U3S*(e/Os}3N7*+U+#;5\W0!-U+zs&>c/Gb2FH/|KZ*Li
 eMcCH0X~${-18~JhYDf3Dc}H1,F<V
X-Url: http://www.cs.berkeley.edu/~padmanab
Mime-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Date: Mon, 11 Aug 1997 13:38:46 -0700
Sender: owner-end2end-interest@ISI.EDU
Precedence: bulk


A paper on the effects of asymmetry on TCP performance, by
Hari Balakrishnan, Randy Katz and myself of the Daedalus
Research Group at U.C.Berkeley, is now available at the
following URLs:

ftp://daedalus.cs.berkeley.edu/pub/papers/tcpasym-mobicom97.ps  (914 KB)
ftp://daedalus.cs.berkeley.edu/pub/papers/tcpasym-mobicom97.ps.gz  (192 KB)

Certain versions of ghostscript may have difficulty displaying
the postscript, but the paper prints fine.

Comments will be most welcome.

-Venkat

-----------------------------------------------------------------------


The Effects of Asymmetry on TCP Performance

Hari Balakrishnan, Venkata N. Padmanabhan, and Randy H. Katz
To appear in Proc. ACM/IEEE Mobicom '97, Budapest, Hungary (Sep. 1997)

In this paper, we study the effects of network asymmetry on end-
to-end TCP performance and suggest techniques to improve it. The 
networks investigated in this study include a wireless cable modem 
network and a packet radio network. In recent literature (e.g., 
[16]), asymmetry has been considered in terms of a mismatch in 
bandwidths in the two directions of a data transfer. We generalize 
this notion of bandwidth asymmetry to other aspects of asymmetry, 
such as latency and media-access, and packet error rate, which are 
common in wide-area wireless networks. 

Using a combination of experiments on real networks and simula
tion, we analyze TCP performance in such networks where the 
throughput achieved is not solely a function of the link and traffic 
characteristics in the direction of data transfer (the forward direc
tion), but depends significantly on the reverse direction as well. We 
focus on bandwidth and latency asymmetries, and propose and 
evaluate several schemes to improve end-to-end performance in 
these cases. These include techniques to decrease the rate of 
acknowledgments on the constrained reverse channel (ack conges
tion control and ack filtering), techniques to reduce source bursti
ness when acknowledgments are infrequent (TCP sender 
adaptation), and algorithms at the reverse bottleneck router to 
schedule data and acks differently from FIFO.