Features/Call Transfer/SIP Flow
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< Features | Call Transfer(Redirected from Functions/Call/Call Transfer/Call Flow)
Attended Transfer
SIP Call Flow
| A | SIP Proxy (SER) | B | SIP Proxy (SER) | C | |||||
|---|---|---|---|---|---|---|---|---|---|
| A initiates call to B | --- INVITE SDP ---> | --- INVITE SDP ---> | ||||||||
| <--- 100 trying --- | | |||||||||
| B is ringing | <--- 180 Ringing --- | <--- 180 Ringing --- | ||||||||
| B accepts the call | <--- 200 SDP OK --- | <--- 200 SDP OK --- | ||||||||
| A acknowledges | --- ACK ---> | --- ACK ---> | ||||||||
| A and B talk | <--- RTP (Audio) ---> | ||||||||
| B places A on Hold | <--- INVITE SDP --- | <--- INVITE SDP --- | ||||||||
| A accepts Hold | --- 200 SDP OK ---> | --- 200 SDP OK ---> | ||||||||
| B acknowledges | <--- ACK --- | <--- ACK --- | ||||||||
| B initiates call to C | --- INVITE SDP ---> | --- INVITE SDP ---> | ||||||||
| C is ringing | <--- 100 Trying --- | | ||||||||
| C is ringing | <--- 180 Ringing --- | <--- 180 Ringing --- | ||||||||
| C accepts the call | <--- 200 SDP OK --- | <--- 200 SDP OK --- | ||||||||
| B acknowledges | --- ACK ---> | --- ACK ---> | ||||||||
| B announces transfer to A | <--- RTP (Audio) ---> | ||||||||
| B presses "transfer" and C is automatically placed on hold | --- INVITE SDP ---> | --- INVITE SDP ---> | ||||||||
| placing C on hold | <--- 100 Trying --- | | ||||||||
| C accepts hold | <--- 200 SDP OK --- | <--- 200 SDP OK --- | ||||||||
| B acknowledges | --- ACK ---> | --- ACK ---> | ||||||||
| B presses "transfer" again and refers A to C | <--- REFER --- | <--- REFER --- | ||||||||
| A accepts the next call goes to C | --- 202 Accepted ---> | --- 202 Accepted ---> | ||||||||
| A initiates call to C | --- INVITE SDP ---> | --- INVITE SDP -----------------------------------------------------------------------------> | ||||||||
| C accepts the call from A | <--- 200 SDP OK --- | <--- 200 SDP OK ------------------------------------------------------------------------------ | ||||||||
| C terminates B call | <--- BYE --- | <--- BYE --- | ||||||||
| B closes C call | --- OK ---> | --- OK ---> | ||||||||
| A informs B to terminate call | --- NOTIFY ---> | --- NOTIFY ---> | ||||||||
| A acknowledges | --- ACK ---> | --- ACK -------------------------------------------------------------------------------------------------> | ||||||||
| A talks to C | <---------------------------------------------------- RTP (Audio) ----------------------------------------------------> | ||||||||
| B receives NOTIFY | <--- OK --- | <--- OK --- | ||||||||
| B terminates A call | <--- BYE --- | <--- BYE --- | ||||||||
| A closes B call | --- OK ---> | --- OK ---> | ||||||||
