(ASCEND) Max dials too fat for switch?

[Phillip Vandry <vandry@Mlink.NET>]

I have a customer who is using a Max 800 with PCMCIA BRI cards to connect
to us with 6 ISDN channels.

This is a dedicated 6 channel connection, so we set it up with Base Ch
Count, Min Ch Count, and Max Ch Count are all set to 6.

Often I see that they are only connected with 2 channels. When this
happens, hanging up and reconnecting rarely helps.

After a lot of debugging, I realized that the Max did indeed attemps to
place additional calls, but the switch returned cause code "41" for
all but the first two.

Because an MPP call works by first establishing one channel, then
negociating the dynamic bandwidth parameters, then immediately adding the
remaining channels to the session simultaneously, my theory is that after
the first call is successful, the DMS 100 switch freaks out when it
sees 5 simultaneous call requests, and it only allows one of them to
proceed.

The workaround is to turn Base Ch Count down to 2, but tune the dynamic
bandwidth parameters so that additional channels will be added very soon,
if not right away (Target Util = 1, Add Pers = 1, etc..). Then the calls
are not simultaneous, and they go through fine.

Anyone seen this before?

I wonder if it could be a mutex in some database lookup on an SCP on the
SS7 side? It's hard to believe the switch could have such a limitation or
bug, but cause code 41 is "Temporary failure", and that sure sounds like
a switch problem to me.

-Phil
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