Take a look at RFC 3326 - the Reason header. It even has an example
covering your case.
Paul
이성우 wrote:
> Dear,
>
> I am implementing a Group Ring facility in a small-sized IP-PBX system that
> uses
> 3 user agents internally. I wonder how I can mark a group ring INVITE message
> to
> differentiate other normal INVITE message? This is for clearing 'missied
> call' log
> at all other user agents except for the one that actually received the call.
>
> Current Scenario is as followings.
>
> 1. Each user agent in IP-PBX system is set to a group ring function.
> 2. There comes a SIP INVITE message from outside to IP-PBX system.
> 3. IP-PBX system forwards the INVITE message to each user agent that are in
> the same ring group.
> 3. Each 3 user agent makes a ring responding 180 message each.
> 4. One user agent receives and send 200 OK back to the caller (IP-PBX system).
> 5. Now that IP-PBX knows it received an answer from a user agent, it sends
> CANCEL to other user agents.
> 6. Each of the 2 user agents process the CANCEL message leaving 'missed call'
> log in its LCD window.
>
>
>
> Caller UA IP-PBX UA1 UA2 UA3
> | INV | | | |
> |----------------->| INV | | |
> | |--------------->| | |
> | | INV | | |
> | |----------------------->| |
> | | INV | | |
> | |------------------------------>|
> | | 180 | | |
> | |<---------------| | |
> | | 180 | | |
> | |<-----------------------| |
> | | 180 | | |
> | |<------------------------------|
> | | 200 | | |
> | |<---------------| | |
> | | ACK | | |
> | |--------------->| | |
> | | CANCEL | | |
> | |----------------------->| |
> | | CANCEL | | |
> | |------------------------------>|
>
>
> My questions are
> Q1. How can I let the user agents know that the incomming INVITE message is
> group-call?
> Q2. If I use a specific SIP Header in the INVITE message (from IP-PBX to UAs)
> to carry
> the group-call infomation, what header should I use and how?
> Q3. Can I use the specific SIP Header in CANCEL message instead of INVITE for
> the same purpose?
>
> Thanks in Advance.
>
>
>
> Lee, Sungwoo
>
> OfficeServ Development/VoIP
> Telecommunication System Div.
> Samsung Electronics Co., LTD.
>
> [EMAIL PROTECTED]
> TEL: 82-31-279-4329
> FAX: 82-31-279-2296
> Mobile: 82-10-3015-4329
>
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