Modem Inactivity Timeout

by Johannes Helmig [Published on 21 Aug. 1999 / Last Updated on 21 Aug. 1999]

In the properties of the Modem,
there is the possibility to define
a timeout: that a connection is
terminated automatically, if no
data ("idle") has been transferred for a
predefined time (often used to ensure,
that a user does not forget to hang-up
and keeps the line occupied for HOURS)
.

This functionality is NOT executed
by the Operating system, but a feature
of the modem: the modem itself is
programmed to terminate the connection.



Modem connection (DUN/RAS) is terminating
You have either no idle-timeout defined or you have not yet reached the
timeout value, but the modem-connection is terminated by the system after
a very short time ?

the Event-Viewer Logs show the
details of the connection.
I had a case, where the connection
was always terminated after
approx. 1 minute.


I found the Microsoft Knowledge Base article Q164257:
"Inactivity Timeout not Passed Through to TAPI Service Provider"

There seems to be a "bug" in NT 4 workstation and server, that with
some(?) / all(?) modem-types the defined timeout value is not properly
programmed into the modem.
The Knowledge base article offers the workaround to switch-off the
timeout by editing the Registry under the key:
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Class
\{4D36E96D-E325-11CE-BFC1-08002BE10318}\000x\Settings:



the Registry-key is usually "0000", but when you had configured multiple
modems or changed to a different modem, it may be a different value
(like the "0002" in the example above)
The key for "InactivityTimeout" shows for my modem "S30=<#>"
(for my modem, the S-register 30 controls the idle-timeout, it maybe a different S-register for your modem).

The article specifies:
"set the entry to the desired value",
so I changed it to 250 (since the User's manual for my
modem lists this s-Register to be programmed in Seconds)


My RAS-server does not terminate the connection quickly or unpredictable,
but now I have a new problem:
My RAS-server does not terminate the connection at all, regardless on
how long the connection has been idle !
(I will keep checking this. If somebody else has a solution, I appreciate to be informed).

The Author — Johannes Helmig

Dr.Johannes Helmig is working as Director, Technical Knowledge Management in the Belgium office of Gerber Technology where he is involved in Customer Service and internal training, with special interest in Networking.

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