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(ASCEND) digital modem code
I'm comparing performance (connect speed) between my new Max 4004s and my
old Xyplex 1620 + rack-mounted Motorola Codex modems.
I typically see connect speeds in the range of 19.2 - 21.6 to the Maxen,
with occasional drops to 9.6 or 14.4 and occasional leaps to 24.0.
I typically see connect speeds in the range of 24.0 - 26.4 to the Motorola
Codex, with occasional leaps to 28.8.
Telco architecture is as follows:
Four analog T1s from LEC terminating on an in-house Nortel Meridian 81c.
PRI from the 81c to the Maxen; analog lines from the 81c to the
rack-mounted bank of Motorola Codex.
I have a single PRI from the LEC to my 81c, and when I hit the Maxen
across this, I get 31.2 - 33.6 every time. (To my mind, this test
eliminates the local PRI, e.g. the 81c to Maxen PRI, as a possible source
of problems.)
(Obvious answer is to replace the analog T1s with PRI ... but there is a
large cost factor here. My company buys its local telephone service from
the LEC across these T1s ... very cheap ... going to PRI means another
30K/yr.)
I've amassed a couple hundred data points now, using various
brands/models of incoming modems, specifically USR 33.6 Sportster &
Courier, Supra 33.6, Codex 28.8.
5.0Ap38 on the Maxen. I've seen the same behavior from 5.0Ap5 through
5.0Ap38.
>From this, I conclude that the Codex chipset does a better job of
handling modem calls across analog T1 than does the Rockwell code in the
Maxen's digital modems.
Can anyone offer me a different explanation? Or more detail as to
why I am seeing this behavior?
--sk
Stuart Kendrick
FHCRC
Seattle, WA
206-667-6974
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