[asterisk-users] progress problems from SIP to PRI

[Klaus Darilion]

Hi Steve!

The problem is following

              PSTN                   PSTN
                |                     |
                |                     |
               E1                     E1
                |                     |
PBX1<--E1-->Asterisk1<---SIP--->Asterisk2<--E1-->PBX2

2 offices. Asterisk between the PBX and the PSTN. Calls between the 
offices are routed directly via SIP (toll bypass).


----SETUP--->
<--SETUPACK--
                 ---INVITE------->
                 <---100----------
                                     ----SETUP--->
                 <---183----------
<--PROGRESS--
                                     <--SETUPACK--
                                     <--CALLPROCEEDING--
                                     <--ALERTING
                 <---180----------
<--CALLPROCEEDING--
<--ALERTING

A user at PBX1 call a user at PBX2. Asterisk 2 sends 183 immediately 
after the SETUP from Asterisk2 to PBX2. This causes Asterisk1 to 
generate a PROGRESS message. Thus PBX1 activates inband audio. But, as 
PBX2 does not generate inband audio, the users at PBX1 do not hear ringback.

As you can see, the 183 causes Asterisk go signal PROGRESS with inband 
audio although there is no inband audio (if there would be inband audio 
PBX2 would send PROGRESS too).


 > My reading of this is that the 183 message you describe is perfectly
 > legal and appropriate. The PRI has made progress by sending a SETUP
 > request.
 >

IMO that's not a real progress. And as you see from the signaling, at 
site 1 there is a PROGRESS message which is not at site 2.

regards
klaus

Steve Davies wrote:
> On 9/25/06, Klaus Darilion <klaus.mailinglists at pernau.at> wrote:
>> Hi!
>>
>> I have problems when bridging from SIP to PRI. As soon as the setup
>> message is sent, Asterisk replies with 183 to the sender.
>>
>> Although there is nor PROGRESS message received, the 183 is sent as the
>> SIP channel received a voice frame and thus activates early media.
>>
>> I wonder why Asterisk reads from the PRI although there was no PROGRESS
>> message received yet.
>>
>> I want to get rid of this 183 - it should be sent only when a PROGRESS
>> is received on the PRI.
>>
>> Can this be configured somehow?
>>
> 
>> From the SIP RFC:
> 
>   "The 183 (Session Progress) response is used to convey information
>   about the progress of the call that is not otherwise classified..."
> 
> My reading of this is that the 183 message you describe is perfectly
> legal and appropriate. The PRI has made progress by sending a SETUP
> request.
> 
> What nature of problem does this cause you? Perhaps there is a better
> solution than stopping legal SIP messages being sent :)
> 
> Regards,
> Steve
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