[PLUG] Modem Connection Speed

[Daggett, Steve]

Jason Van Cleve:
> Can somebody explain how to check the actual speed of a modem 
> connection?

  It's surprisingly tough to do from a PC.  One way is to use minicom (or
some other term program) to connect to your modem and use AT commands to
check your link stats.  You need to set your modem to "Ignore DTR" before
you start with "AT&D0".  This prevents the modem from hanging up and
clearing its registers when you kill pppd.  

1) Use minicom to set DTR to ignore.  AT&D0
2) Dial up your ISP and surf.
3) Kill pppd to release the serial port.
4) Use minicom and AT commands to read the TX/RX stats.  

  Here's the fun bit, the AT commands aren't standard.  Each modem chipset
will use a different command string(s).  Some modems don't have stats at
all.  This site has a list of the more common commands.  

http://www.modemsite.com/56k/diag.asp

> 
> wvdial says "CONNECT 115200" after dialing the number, but 
> I'm pretty sure that's not an indication of the established 
> speed.  That's just read from wvdial.conf.

  The CONNECT speed may be correct or it may only be the speed of the serial
port.  Modern modem chips are actually intelligent little communication
coprocessors.  The serial port is often running at a fixed speed.  The modem
buffers the data to match the real line speed to the serial port speed.  The
real line speed is constantly being renegotiated and changed as necessary.

  One handy trick is to use AT commands to set a minimum speed in your
modem.  Your modem will disconnect if the line tries to negotiate below that
level.  The higher speed AT commands are non-standard.  You will have to
check the docs for your modem.  

There are many web based speed testers:
http://us.mcafee.com/root/speedometer.asp

a whole Google directory of them:
http://directory.google.com/Top/Computers/Data_Communications/Testing_and_To
ols/?tc=1/

  If you're talking to another *nix box, there is a very nice little utility
called "bing", for Bandwidth Ping.  It's great for monitoring actual
bandwidth between machines from a script.  

http://www.cnam.fr/reseau/bing.html

Steve D...