<br><div class="gmail_quote">we have tested newreno (only ietf standard), bic (linux default), cubic
and westwood+ over commercial hsdpa card. we run 3000 experiments (down
and up links).<br>main results were:<br>1. similar downlink goodputs
but with much more timeouts and packet loss ratio when using bic/cubic
(3 times timeouts and 2 times packet loss ratio)<br>
2. larger rtt experienced when using bic/cubic<br><br><br>also cwnd dynamics do not look great!<br><br>more details can be found at:<div class="Ih2E3d"><br><br><a href="http://c3lab.poliba.it/index.php/TCP_over_Hsdpa" target="_blank">http://c3lab.poliba.it/index.php/TCP_over_Hsdpa</a><br>
<br></div><font color="#888888">saverio<br><br></font><div class="gmail_quote"><div class="Ih2E3d">On Fri, Nov 14, 2008 at 8:58 AM, denis.collange <span dir="ltr"><<a href="mailto:denis.collange@orange-ftgroup.com" target="_blank">denis.collange@orange-ftgroup.com</a>></span> wrote:<br>
</div><blockquote class="gmail_quote" style="border-left: 1px solid rgb(204, 204, 204); margin: 0pt 0pt 0pt 0.8ex; padding-left: 1ex;"><div><div></div><div class="Wj3C7c">
<div>
<br>
<p><font size="2" face="Courier New">Hello,</font>
</p>
<p><font size="2" face="Courier New">We have a question concerning the Compound TCP draft, along the lines of point 4 in </font><a href="http://oakham.cs.ucl.ac.uk/pipermail/iccrg/2008-March/000468.html" target="_blank"><u><font color="#0000ff" size="2" face="Courier New">http://oakham.cs.ucl.ac.uk/pipermail/iccrg/2008-March/000468.html</font></u></a><font size="2" face="Courier New"> ("4. What happens to dwnd during slow-start, and when is slow-start exited?")</font></p>
<p><font size="2" face="Courier New">The draft states that "dwnd is initialized to zero while the connection is in slow start" (p. 6), and then "Delay-based component only kicks in when cwnd is larger than some threshold, currently set to 38 packets assuming 1500 byte MTU" (p.11).</font></p>
<p><font size="2" face="Courier New">However, starting from zero, the recursion (3) on p. 7 gives a negative value, so that dwnd would always be set to 0. In order for dwmd to be positive the initial value needs to be such that: </font></p>
<p> <font size="2" face="Courier New">alpha*dwnd(t)^k - 1 > 0</font>
<br><font size="2" face="Courier New">(if dwnd is restricted to integer values a larger initial value might be needed depending on how the rounding is done).</font>
</p>
<p><font size="2" face="Courier New">Clearly an initial value of 38 does satisfy this requirement but it is not clear whether this is the initial value that should be assigned to dwnd after slow-start or when the cwnd is larger then the specified threshold (38 in the draft). </font></p>
<p><font size="2" face="Courier New">We think that the draft should clearly state the initial value for dwnd every time the delay component is activated. It might also be interesting to comment on why the window update function is not the same as in the previously published papers about Compound TCP. </font></p>
<br>
<p><font size="2" face="Courier New">Thanks,</font>
</p>
<p><font size="2" face="Courier New">Denis and Alberto</font>
<br><font size="2" face="Courier New"> </font>
</p>
</div>
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<br></div></blockquote></div><div><div></div><div class="Wj3C7c"><br><br clear="all"><br>-- <br>Prof. Saverio Mascolo<br>Dipartimento di Elettrotecnica ed Elettronica<br>Politecnico di Bari<br>Via Orabona 4<br>70125 Bari <br>
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</div></div></div><br><br clear="all"><br>-- <br>Prof. Saverio Mascolo<br>Dipartimento di Elettrotecnica ed Elettronica<br>Politecnico di Bari<br>Via Orabona 4<br>70125 Bari <br>Italy<br>Tel. +39 080 5963621<br>Fax. +39 080 5963410<br>
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