Hi, You can use Method 2, assuming the 18x and 200 have different To tag values. Otherwise you can use Method 3 or 4 (message 9 in Method 3, and message 7 in Method 4, seem to go in the wrong direction, though). Regards, Christer
________________________________
From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED]
Sent: 2. lokakuuta 2006 12:57
To: [email protected]
Cc: [email protected]
Subject: [Sip] Early media query
Hi,
I want to made an application where we can use early media for
playing initial in-band announcements, and then finally connecting the
caller to actual callee (eg prepaid card application).
I want to know which is the correct way to support this as per
SIP RFC.
Method 1:
Caller Callee
| |
| |
|(1) INVITE with offer |
|---------------------------->|
| |
| |
|(2) 183 with answer 1 |
|<----------------------------|
| |
| |
|(3) 200 OK with SDP |
|<----------------------------|
| |
| |
|(4) ACK |
|---------------------------->|
| |
(2) contains SDP of announcement server
(3) contains SDP of callee
Method 2:
Caller
Callee
| |
| |
|(1) INVITE with offer |
|---------------------------->|
| |
| |
|(2) 183 with answer 1 |
|<----------------------------|
| |
| |
|(3) PRACK |
|---------------------------->|
| |
| |
|(4) 200 PRACK |
|<----------------------------|
| |
| |
|(5) 200 INVITE with sdp |
|<----------------------------|
| |
| |
|(6) ACK |
|---------------------------->|
| |
| |
| |
| |
(2) contains SDP of announcement server
(5) contains SDP of callee
Method 3:
Caller Callee
| |
| |
|(1) INVITE with offer |
|---------------------------->|
| |
| |
|(2) 183 with answer 1 |
|<----------------------------|
| |
| |
|(3) PRACK |
|---------------------------->|
| |
| |
|(4) 200 PRACK |
|<----------------------------|
|(5) 200 OK |
|<----------------------------|
| |
|(6) ACK |
|---------------------------->|
| |
|(7)Re-INVITE with SDP |
|<----------------------------|
| |
| |
|(8) 200 OK with SDP |
|---------------------------->|
| |
|(9) ACK |
|---------------------------->|
(2) contains SDP of announcement server
(5) contains no SDP
(7) contains SDP of callee
(8) contains answer of caller for callee offer
Her, UDATE can also be used instead of Re-invites.
Method 4:
Caller
Callee
| |
| |
|(1) INVITE with offer |
|---------------------------->|
| |
| |
|(2) 183 with answer 1 |
|<----------------------------|
| |
| |
|(3) PRACK |
|---------------------------->|
| |
| |
|(4) 200 PRACK |
|<----------------------------|
|(5) UPDATE (callee offer) |
|<----------------------------|
| |
|(6) 200 UPDATE (answer) |
|---------------------------->|
| |
|(7) 200 INVITE |
|---------------------------->|
| |
|(8) ACK |
|---------------------------->|
In this case, when callee answers, UPDATE is sent to caller to
negoitate audio with caller, and then 200 OK is sent for the initial
INVITE.
Regards,
Udit
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