(PM) Increase in "Call Circuit Closed" disconnects - ComOS 3.8

John Vozza (john@netrom.com)
Sun, 22 Nov 1998 12:26:37 -0500 (EST)

Since installing ComOS 3.8, I have been seeing an alarming number of call
circuit closed disconnects. As as been discussed MANY times in the past
this type of disconnect has been explained to mean that for SOME reason
the remote side has terminated the call and the PM3 received a signal to
terminate the call from the telco switch. (I use exclusively PRI's)

PLEASE, before flaming me, READ completely what I'm about to say!

I have done extensive testing on this issue and yes the PM3 is responding
to the signal from the telco switch. HOWEVER, the PM3 appears to be
CAUSING some, (all?) of the remote side disconnects by DROPPING the PM3
side modem!

Allow me to justify my conclusion. Tracing the CCC (Call Circuit Closed)
has been difficult but working with several competent end users we have
found, via ati11 or at&v1 depending on modems, that the client side is
seeing a "lost carrier" and terminating the call as it should and
increasing the setting for carrier interruption has no effect. My original
thought was padding, or other telco problem ie; bad lines, noise, etc. I
no longer believe that this is just a telco issue though.

Last night, while working with an MPPP customer I noticed that they only
had 1 modem up so I wanted to disconnect the remaining modem and force
their side to re-dial. Inadvertently I did a "reset Mx" instead of "reset
Sx" and lo and behold after a few second pause I saw the CCC termination
message for that session. This is 100% reproducible on my PM3's Also, no
admin reset message was generated. (Yes my stupidity)

To clarify my point, as well as my question, MZ and others have said that
CCC disconnects are NOT caused by the PM3 but I submit that while
technically correct that is not always the case. Since the PM3 can "drop
carrier" due to "operator error" can it not also "drop carrier" due to a
modem code or OS bug?

I have BCC'd this to support as well and details of the PM3's are;

ComOS 3.8
All show line[0-1] are clean, 0's across the board.
All are PRI's from either 5ESS or Seimens switches
Memory is 4MB
All modules on except BGP

John
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