SIP REFER issue

Asterisk Asterisk Support
1

Hi folks,

Been working w/ Asterisk for a little while, but never used Transfer() (SIP REFER).

I have a call coming in directly from a VoIP provider. Call terminates on Asterisk box.

Transfer() works fine if I do this (simplified example with key info redacted):

exten => 1234,1,Noop(Test of TRANSFER capability)
exten => 1234,n,Wait(1.0)
exten => 1234,n,Transfer(770xxxxxxx@xxx.xxx.xxx.xxx)
exten => 1234,n,Noop(TRANSFERSTATUS is ${TRANSFERSTATUS})

I get SUCCESS.

However, if I Answer() the call, I get FAILURE:

exten => 1234,1,Noop(Test of TRANSFER capability)
exten => 1234,n,Answer(1000)
exten => 1234,n,Transfer(770xxxxxxx@xxx.xxx.xxx.xxx)
exten => 1234,n,Noop(TRANSFERSTATUS is ${TRANSFERSTATUS})

What I need:

Party A calls Asterisk (who is Party B in this example)
Party B answers and some things get done, interacts with Party A, etc.
Party B wants to push the call back into the cloud to Party C and initiates a Transfer()

Any help woiuld get appreciated.

2

Asterisk version is critical here. In 1.4 and at least some 1.6, REFER transfers are pretty broken, especially when the transfer fails.

You definitely need to take a SIP trace here.

I think Transfer is very little used.

3

Asterisk version 1.8.0

The trace shows Method Not Allowed.

So how do people avoid hairpins within their switch if one can’t perform a SIP REFER to push a call back into the cloud and to a new destination? Seems like a blind transfer would be something people would use often and would be a strong selling point for VoIP.

4

Using external media (canreinvite = yes, or more recently, directmedia = yes) gives most of the advantages.

If you are getting Method Not Allowed, this is a commercial decision by you service provider, not a limitation of Asterisk. Most providers will charge you as though the call hairpinned, if they did allow redirects.