[cisco-nas] AS5300 Dropped Calls

[Mark Tinka]

Hi all.

I have a situation where some customers may drop calls after a few 
seconds-to-minutes of dial-up connection. In some cases, either the phone 
line (noisy), modem or modem driver has been the cause, and problem 
rectified.

In other cases, phone line's good (even less than <= 800m from CO), modem and 
modem configuration are in order, but the line will still cut after a few 
moments of connectivity.

The AS5300 has been configured for 56K access. I have tried different 
modulation schemes to try and solve this problem, testing v.90 and v.92 (v.34 
won't offer over 33.6Kbps, and some customers can support 52Kbps with no line 
drops, but haven't tested it long enough to confirm problem resolution).

So I left the async lines to auto-negotiate line parameters with the customer 
once they connect, but that doesn't seem to have solved the problem. What's 
strange is that a previous purely analog NAS didn't have this problem (unless 
the customer had an idle-timeout set).

Anyone have any idea how the AS5300 can be tuned to deal with this? PRI lines 
have been delivered on HDSL/G.703, and D-channel interfaces on the AS5300 
aren't reporting any line errors.

All help appreciated.

Mark.