[asterisk-dev] Advice of Charge project

[Klaus Darilion]

Am 12.03.2010 17:26, schrieb Kevin P. Fleming:
> Klaus Darilion wrote:
>
>> Do you have ideas how to solve the problem, e.g. introducing something
>> like a "delayed release" and keep the hanging up channel alive until the
>> AOC information is available?
>
> That's not really possible for SIP, for example. If the remote endpoint
> sends you a BYE, you can't send them any other signaling until you
> respond to that BYE, and you can't reject it or delay it. If you do
> manage to send them signaling, you'd likely receive a '491 Request
> Pending' response in return, and a re-transmission of the BYE. For SIP,
> at least, there is no 'post-call' signaling possible.

According to SNOM's spec the AOC is sent as a header. Thus, it could be 
added to the 200 OK of the BYE request. This would mean that the 200 OK 
needs to be delayed until the AOC-E is received from the bridged 
channel. That's ugly but it would work. But anyway, I think there is not 
necessary to send detailed AOC-E to SIP clients.

> The only practical way that I could see AOC-E being handled over SIP is
> for the endpoint to SUBSCRIBE to some sort of AOC-E event package, and
> then the server could send a NOTIFY if and when the AOC-E data becomes
> available, including in the event package the Call-ID and tags of the
> call the AOC-E is related to.

That would work too.

I think the more important scenarios are:
1. between ISDN technologies, e.g. Asterisk is located between the 
legacy PBX (which processes AOC) and the telco switch. Here, when the 
internal user hangs up (DISCONNECT), the RELEASE could be delayed until 
the RELEASE was received on the outgoing channel and AOC-E information 
is available to be sent.

2. Asterisk generating AOC. This is often needed for hotels which put an 
Asterisk server in front of their PBX for SIP/IAX trunking and LCR. They 
often need AOC information to calculate the the prices for the phone 
calls made from the hotel rooms. Here, the RELEASE needs not be delayed, 
but there needs to be some AOC-generator engine inside of Asterisk to 
produce the AOC according to defined rates.

regards
klaus