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Tl Posts:

Posted - 11/25/2005 5:25:32 AM  Show Profile  Email Poster  Edit Message
My soft CXT AC-Link modem regularly connects at 48K.
Sometime at 49.2K, so that I think a phone line condition
is normal. But I cannot achieve max throughput. In article
"Monitoring & Determining Throughput" at, I see that the
author's modem at 48K connection can receive with upto 50K
rate. But my modem never downloads above 36K. I monitor it
by Net.Medic and downloading a well compressed file from
the nearest server: my ISP. Of course, downloading HTML and
other text increases the modem throughput due to compression.
I think may be my WinXP's TCP/IP settings are not configured
optimally? The MTU of the ISP is 1500, so I didn't change
my system's MTU. The ReceiveWinSize is large, above 128KB.

Here's how my modem connections:

Recv: <cr><lf>+MCR: V90<cr><lf>
Interpreted response: Informative
Recv: <cr><lf>+MRR: 48000<cr><lf>
Interpreted response: Informative
Recv: <cr><lf>+ER: LAPM<cr><lf>
Interpreted response: Informative
Recv: <cr><lf>+DR: V42B<cr><lf>
Interpreted response: Informative
Recv: <cr><lf>CONNECT 48000<cr><lf>
Interpreted response: Connect
Connection established at 48000bps.
Error-control on.
Data compression on.

Tl Posts:

Posted - 11/26/2005 1:13:48 PM  Show Profile  Email Poster  Edit Message
I use the speedtest at as my benchmark.

I've tested several different modems, and most get in the range of 32-35 kbps as reported by Speedtest. A lot depends upon the ISP that I call, and every connection seems a little different.

I just tested a new U.S Robotics 5660 Software Modem that I purchased for $9.95 after rebate. Speedtest reported 36 kbps which is 4.5 KBytes per second.

I think the best I have seen using Speedtest is 40-41 kbps.

With my Agere SV92PL software modem I need to limit the connect speed to get the best throughput.

Your modem may be doing just fine at 36 kbps.


Tl Posts:

Posted - 11/30/2005 11:51:35 AM  Show Profile  Email Poster  Edit Message  v.Richards Homepage
Suggest taking a look at the modem's post-call diagnostics in particular to see if there are any retrains/rate renegotiations; to see if the *final* receive/xmt rate matches the intial rates, etc.

Then, you could try limiting the connect speed to slightly lower rates to see if there is any improvement in throughput/overall performance.

Aloha! Richard.

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