[Asterisk-Users] Re: Grandstream transfer into outer space

[Stephen R. Besch]

Olle E. Johansson wrote:
> Stephen R. Besch wrote:
> 
>> Olle E. Johansson wrote:
>>
>>> Going back to the subject, what does the grandstream really do, 
>>> SIP-wise, when you press
>>> the transfer button?
>>>
>>
>> 4.3.7 Call Transfer The user can transfer an active call to a third 
>> phone by using the “Transfer” button. The sequence is like this: The 
>> user presses the “Transfer” button and if the other voice channel is 
>> available (i.e., there is no other active conversation besides the 
>> current one), he/she will hear a dial tone. He/She can then dial the 
>> 3rd phone and then hangs up his own phone. 2 kinds of blind call 
>> transfers are supported: using REFER and using BYE/Also. The SIP 
>> message flow based on SIP REFER method looks something like this:
>>
>> Call Flow Diagram For Blind Call Transfer:
>>
>>  From Transferee to Transferor
>>
>>      INVITE ->
>>     <-100/180/200
>>      ACK ->
>>     <- RTP Media ->
>>     <- REFER
>>      202 ->
>>      NOTIFY ->
>>     <- 200
>>     <- BYE
>>      200 ->
>>
>>  From Transferee to Recipient
>>
>>     INVITE ->
>>     <-  100/180/200
>>      ACK ->
>>     <- RTP Media ->
>>
>>
>> The SIP message flow based on BYE/Also  method looks something like this:
>>
>>  From Transferee to Transferor
>>
>>      INVITE ->
>>     <- 100/180/200
>>     ACK ->
>>     <- RTP Media ->
>>     <- REFER
>>     501 Not Implemented ->
>>     <- BYE with “Also:”
>>     200 ->
>>
>>  From Transferee to Recipient
>>     INVITE ->
>>     <- 100/180/200
>>     ACK ->
>>     <- RTP Media ->
>>
>> I have no idea if this is accurate, I just copied it and replaced the 
>> arrows indicating direction with "->" and "<-". You can download the 
>> manual itself from the GS web site.
> 
> I'll do that.
> 
> Does Asterisk work with this transfer button or not? We have 
> implementation of both REFER
> and BYE/also in the sip channel.
> 
In my setting, yes it does.  I've been thinking of trying transfers like 
these on the GS: 1) hit flash to get second line,  2) dial party to 
transfer to,  3) arrange transfer and have them hang up, 4) flash back 
to the original caller and do a blind transfer.

Still, this does not fix the problem with the outer space transfers.

Stephen R. Besch.