[asterisk-users] Best way to know a call is being transfered

Jonathan H lardconcepts at gmail.com
Mon May 29 03:16:24 CDT 2017

Well, once you've upgraded to a version of Asterisk which didn't
become "EOL - DO NOT USE - NO FIXES" (!) almost 2 years ago, then you
might be able use logging which was introduced 5 years ago in Asterisk
11. Although the "transfers" section in the info below says it "can be
a little tricky...". Read on!



Call ID Logging (which has nothing to do with caller ID) is a new
feature of Asterisk 11 intended to help administrators and support
givers to more quickly understand problems that occur during the
course of calls. Channels are now bound to call identifiers which can
be shared among a number of channels, threads, and other consumers.


Transfers can be a little tricky to follow with the call ID logging
feature. As a general rule, an attended transfer will always result in
a new call ID being made because a separate call must occur between
the party that initiates the transfer and whatever extension is going
to receive it. Once the attended transfer is completed, the channel
that was transferred will use the Call ID created when the transferrer
called the recipient.

Blind transfers are slightly more variable. If a SIP peer 'peer1'
calls another SIP peer 'peer2' via the dial application and peer2
blind transfers peer1 elsewhere, the call ID will persist. If on the
other hand, peer1 blind transfers peer2 at this point a new call ID
will be created. When peer1 transfers peer2, peer2 has a new channel
created which enters the PBX for the first time, so it creates a new
call ID. When peer1 is transferred, it simply resumes running PBX, so
the call is still considered the same call. By setting the debug level
to 3 for the channel internal API (channel_internal_api.c), all call
ID settings for every channel will be logged and this may be able to
help when trying to keep track of calls through multiple transfers.

On 29 May 2017 at 08:17, Jonas Kellens <jonas.kellens at telenet.be> wrote:
> Hello
> using Asterisk
> What is the best way of knowing a call is being transfered (attended and
> unattended) ? And also knowing whereto (sip user) the call is being
> transfered and who is the transferer ?
> So I can log this information.
> Kind regards.
> J.
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