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<DIV><FONT face=Arial size=2>Hi all,</FONT></DIV>
<DIV> </DIV>
<DIV><FONT face=Arial size=2>at <A
href="http://www-ictserv.poliba.it/mascolo/recent_research/recent_research.htm">http://www-ictserv.poliba.it/mascolo/recent_research/recent_research.htm</A></FONT></DIV>
<DIV><FONT face=Arial size=2></FONT> </DIV>
<DIV><FONT face=Arial size=2>you can find a copy of the paper</FONT></DIV>
<DIV> </DIV>
<DIV><FONT face=Arial size=2>Saverio Mascolo, Claudio Casetti, Mario Gerla, M.
Y. Sanadidi, and Ren Wang, “<I><A
href="http://www-ictserv.poliba.it/mascolo/papers/mobicom01.pdf">TCP Westwood:
Bandwidth Estimation for Enhanced Transport over Wireless Links</A></I>” ACM
Mobicom 2001, July 16-21, Rome, Italy. </FONT></DIV>
<DIV> </DIV>
<DIV><FONT face=Arial size=2>
<P class=HTMLPreformatted style="LINE-HEIGHT: 90%; TEXT-ALIGN: justify"><B><SPAN
lang=EN-US
style="FONT-FAMILY: 'Times New Roman'; FONT-SIZE: 12pt; LAYOUT-GRID-MODE: line; mso-bidi-font-size: 10.0pt; mso-bidi-font-style: italic">Abstract<?xml:namespace
prefix = o ns = "urn:schemas-microsoft-com:office:office"
/><o:p></o:p></SPAN></B></P>
<P class=MsoNormal style="TEXT-ALIGN: justify"><SPAN lang=EN-US
style="FONT-SIZE: 9pt; LAYOUT-GRID-MODE: line; mso-bidi-font-size: 10.0pt">TCP
Westwood (TCPW) is a sender-side modification of the TCP congestion window
algorithm that improves upon the performance of TCP Reno in wired as well as
wireless networks. The improvement is most significant in wireless networks with
lossy links, since TCP Westwood relies on end-to-end bandwidth estimation to
discriminate the cause of packet loss (congestion or wireless channel effect)
which is a major problem in TCP Reno.<SPAN style="mso-spacerun: yes">
</SPAN>An important distinguishing feature of TCP Westwood with respect to
previous wireless TCP “extensions” is that it does not require inspection and/or
interception of TCP packets at intermediate (proxy) nodes. Rather, it fully
complies with the end-to-end TCP design principle. The key innovative idea is to
continuously measure at the TCP source the rate of the connection by monitoring
the rate of returning ACKs. The estimate is then used to compute congestion
window and slow start threshold after a congestion episode, that is, after three
duplicate acknowledgments or after a timeout. The rationale of this strategy is
simple: in contrast with TCP Reno, which "blindly" halves the congestion window
after three duplicate ACKs, TCP Westwood attempts to select a slow start
threshold and a congestion window which are consistent with the effective
bandwidth used at the time congestion is experienced. We call this mechanism <I
style="mso-bidi-font-style: normal">faster recovery</I>. The proposed mechanism
is particularly effective over wireless links where sporadic losses due to radio
channel problems are often misinterpreted as a symptom of congestion by current
TCP schemes and thus lead to an unnecessary window reduction. </SPAN><SPAN
lang=EN-US style="FONT-SIZE: 9pt; mso-bidi-font-size: 10.0pt">Experimental
studies reveal improvements in throughput performance, as well as in fairness.
In addition, friendliness with TCP Reno was observed in a set of experiments
showing that TCP Reno connections are not starved by TCPW connections. Most
importantly, TCPW is extremely effective in mixed wired and wireless networks
where throughput improvements of up to 550% are observed. Finally, TCPW performs
almost as well as localized link layer approaches such as the popular Snoop
scheme, without incurring the O/H of a specialized link layer protocol.
<o:p></o:p></SPAN></P></FONT></DIV>
<DIV><FONT face=Arial size=2></FONT> </DIV>
<DIV><FONT face=Arial size=2>-----------<BR>Saverio Mascolo, Ph.D<BR>Associate
Professor<BR>Dipartimento di Elettrotecnica ed Elettronica, Politecnico di
Bari<BR>Via Orabona 4, 70125 Bari, Italy<BR>email: <A
href="mailto:mascolo@poliba.it">mascolo@poliba.it</A><BR>tel. +39 080
5963621<BR>fax. +39 080 5963410<BR><A
href="http://www-dee.poliba.it/dee-web/Personale/mascolo.html">http://www-dee.poliba.it/dee-web/Personale/mascolo.html</A></FONT></DIV></BODY></HTML>