[asterisk-users] [SOLVED + EXPLANATION]: Strange ISDN-problem with incoming calls out of the same city

[Stefan Guenther]

Hi,

in december last year I posted the following problem:

<QUOTE>
When I dial the number of our client, located in another town, I get a
connection to the asterisk server, I can talk to my client or listen to
his mailbox.

If someone in the town of this client calls him, he gets the ISDN error
"service not available".

With some more debugging we saw what happens with these specific calls.
For some reason local calls and calls from a few other cities cause
trouble, because asterisk doesn't get the whole number that has been
dialed. If e.g. someone from the same town dials 123456, asterisk only
gets  12345 or 1234. This extension doesn't exist in the dialplan and so
the call fails. And this is not a single failure, it happens every time.
</QUOTE>

We were finally able to track down this problem and solve it.
I'm not sure whether it is only related to ISDN, but maybe some of you
find this explanation helpful.

This description deals with the German Telecom, as far as I know Colt 
Telecom handles things the same way.

There are two ways to transfer a telephone number, either digit by digit 
or as a whole block. Mobile phone company e.g. always transfer number as 
a block.

The German Telecom is able to switch from digit-by-digit (which is the 
default) to block transfer, but they can do this only for a defined 
number of digit. If they set a length of e.g. 8 digit, they can not 
predict what will happen to a call that has more or less numbers.

For us that meant that we had to look for a solution that solves the 
problem on the ISDN card. EICON support gave us a number of valueable 
hints on how to configure DID and to set a timeout of 2 seconds. Which 
means that the card would only wait 2 seconds for the whole number to 
transfer. This settings is ridiculous! According to a support guy from 
German Telecom (yes, I know most Germans won't believe that German 
Telecom has support guys with a deeper knowledge - believe me they 
have!!) that default timeout is 12 seconds. We decided to use 14 seconds 
on the EICON card. That means 14 seconds between pressing and sending 
the first digit and the end of the transfer.

The asterisk server now finally gets all calls.
If someone is interested in screenshots of the configuration of the 
EICON card or any other details, just send me an email.

I would appreciated if some of you could post their experience with 
other telcos in other countries. Do they use digit-by-digit or block 
transfer? Is this only a question of ISDN or does it appear on analogue 
lines, too?

Stefan

-- 

********************************************
in-put GbR - Das Linux-Systemhaus
Stefan-Michael Guenther
Geschaeftsfuehrer
Moltkestrasse 49     D-76133 Karlsruhe
Tel./Fax : +49 (0)721 / 83044 - 98/93
http://www.in-put.de
********************************************
      Schulungen  Installationen
          Beratung   Support
       Voice-over-IP-Loesungen
********************************************