Slightly off-topic: modem troubles

Eric Fagan ( (no email) )
Wed, 1 Apr 1998 14:13:11 -0700

Hello: This req for help only applies to anyone with telecom experience (or
good working knowledge of modem comms) - Other people can probably ignore
this, thx.

One of my pops in a US West area is having severe difficulties
establishing error-free connections between modems. We've got Hayes Century
II-16's, MR200 analogs, & stand-alone Cardinal MVP-33.6 modems at this site.
All are configured with manufacturer recommended init strings for ISP's.
For unknown reasons, client modems attempting to establish carrier with
these modems do not connect correctly and are forced into connecting without
error correction on 40-60% of the calls. This issue arises once every
several months and lasts from 3 days to a month. The 28.8 or 33.6 client
modems are configured in win95 with standard "error free connection,
compress data" -- no deviation from the defaults. The modem sounds as if
it is handshaking normally -- however, after the modem mutes, (usually the
point at which you receive a "connect" message), there is a 5-10 second
pause in which nothing happens. After the pause, the "connect" message
appears followed by streaming garbage. This affects all client modems, from
cheapies to USR's.
Win95 always interprets this the same: It will show "status: dialing"
while handshaking, and then continue to show that message for several
seconds after the modem mutes (not normal). It'll switch to "verifying
username & password" for a few secs & then die with "unable to negotiate a
compatible set of network protocols," etc. Sometimes the client modem
becomes totally unusable after this happens and will not connect to anything
again until it is powered down & brought back up.
US West says the lines are clean -- I've looked at the results myself.
Low loss, background noise, etc. However, these tests they perform only
test from the pop to the switch -- they refuse to do an end-to-end. I
highly suspect that the problem is in the switch -- perhaps overmodulation,
or .???
Anyway, apologies for posting this on the NT-ISP list -- it's more
general-ISP, but I'm out of options. This latest bout has been going on for
weeks. If anyone has any suggestions or experience with this, please email
me off-list.

Eric Fagan