[comp.protocols.misc] Using High Speed Modems

wardc@banana.cse.eng.auburn.edu (Christopher Ward) (05/20/91)

Greetings friends in netland.  I am currently evaluating some in-house
software for a client and would like some "in reality" information on a
communications product they are using.  Perhaps you can help on one of
the questions listed below.  Your interest in appreciated.

1) They will be using US Robotics HST/V.42bis 14.4K data compression
modems for communications, these modems automatically step down to
slower speeds if the line is of poor quality.  The sites may be anywhere
in the US.  Does anyone know approx % of connections or time that modems
will slow down, and to what extent (perhaps there has been a study in
..?)  E.g.  5% of connections can be expected to only operate at 4.8K.

2) Again, with the modems above.  I was experimenting by sending data
records between stations.  The data was 1K records of mostly spaces
which I would have thought would be compressed.  Just for kicks I
decided to change the records to be random characters instead (random
typing on the keyboard).  Suprise!  The transfer times were exactly the
same.  It would seem that either the compression algorithm is very
efficient or not working!  And yes, I did have the modem's compression
enabled (&K3 for those in the know).  Any ideas?

I will follow up with any pearls of wisdom I receive.

Thanks
Chris Ward

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grohol@novavax.UUCP (John Grohol) (05/25/91)

wardc@banana.cse.eng.auburn.edu (Christopher Ward) writes:

>1) They will be using US Robotics HST/V.42bis 14.4K data compression
>modems for communications, these modems automatically step down to
>slower speeds if the line is of poor quality.  The sites may be anywhere
>in the US.  Does anyone know approx % of connections or time that modems
>will slow down, and to what extent (perhaps there has been a study in
>..?)  E.g.  5% of connections can be expected to only operate at 4.8K.

From my own personal experience, as well as what I've read in USR's
manual and magazine articles, you can expect most xfers to go
through at 19.2k or higher. Of course your long distance carrier may
be an important factor in this chain, so it may be worth your while
to change ld carrier if you do indeed find that your modems are
often stepping down because of line noise.

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 John M. Grohol                     ||  Nova University - Ft. Lauderdale, FL
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