[asterisk-ss7] CPG/ACM

Matthew Fredrickson creslin at digium.com
Mon Mar 10 16:21:57 CDT 2008

Matthew Fredrickson wrote:
> asterisk at nicox.org wrote:
>> Hello,
>> I'm using the libss7 with svn-version 98 and have a bit problem with 
>> dialing some numbers.
>> The Problem: If i dial to a fi8xed network number and the carrier gives 
>> back a ACM asterisk does not send a Alerting to the connected E1/PRI, If i 
>> get a CPG from the carrier, anything is fine.
>> in SS7-Documentations i see that CGP and ACM is a Alerting and means not 
>> correct the same, but both means  that the dialed side is ringing.
>> Does anybody have the same problem, or any idea for a patch, or is this 
>> patched in a newer version of libss7?
> As I understand it, ACM is equivalent to the PRI PROCEEDING message, 
> which means that the number dialed is indeed a valid number and 
> something is being done with it (but exactly what is not indicated). 
> So, at least in chan_zap as it exists right now, when we receive an ACM 
> message, we pass an AST_CONTROL_PROCEEDING back into the core.  If this 
> is incorrect behavior and someone has some documentation to prove that, 
> I certainly would like to see this corrected.
> One thing you might want to do is to update your libss7 version (as we 
> are now at rev 144, as well as your Asterisk version.
> Another thing that you could try is to add the 'r' flag to your Dial() 
> statement, as that will cause ringing to indicate pretty much regardless 
> of what's going on.

I have subsequently looked at this and am less confident about what I 
said above.  It appears that in Q.764 we should immediately connect the 
  audio transmission path after sending an IAM.   I'm looking more into 
this, and will probably commit an update to chan_zap so that the 
transmission path is connected immediately instead of after receiving a CPG.

If anyone has anymore comments or experience with regards to my proposed 
solultion, please speak now or hold your peace :-)

Matthew Fredrickson
Software/Firmware Engineer
Digium, Inc.

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