[Freeswitch-users] Transfers and billsecs

[Isaac Jurado]

Hello all,

First of all, I want to apologize for the length of this message.  I
wouldn't like to waste anyone's time.

I'm new to this list and also fairly new to the VoIP world.  I work for
a company that provides some basic telephony services using FreeSWITCH.
Recelty, we sketched up a plan to extend the features of our service to
the customers; so we started experimenting first.

Our setup is a basic HTTP server that controls FreeSWITCH through
mod_xml_curl and processes call information afterwards, with the
information provided by mod_xml_cdr.  In general, each customer has its
own context and we are trying to come along with a general billing
system that tries to be as fair as possible.

In order to reduce billing system complexity, we are completing channel
information from the dialplan so we can inspect each CDR generated
independently, and be able to discard it or process it on its own,
without having to check other related CDRs.

Obviously, this is becoming harder and harder after we started dealing
with call transfers, either attended or blind.  Consider the following
scenario:

  1. We have four customers: A, B, C and D.

  2. A calls B, the complete billing information is in the a-leg (from A
     to FS) and it will be charged as a call to B.

  3. After some time (say 20 seconds), B makes a blind transfer to C.
     So a new b-leg is created (from FS to C), the channel between FS
     and B is closed and a CDR is generated.  Conceptually, this is a
     call from B to C which should be charged to B, not to A.

  4. Again, after some time (say 30 seconds), C makes a blind transfer
     to D.  Similar procedure: new channel from FS to D and the channel
     from FS to C terminates, generating a CDR.  This time, we should
     charge a call from C to D.

  5. After 15 seconds, A or D hang up and two more CDRs are generated.

In the end, the billing system should charge:

  - The call between A and B, which had a duration of 65 seconds.
  - The call between B and C, which had a duration of 45 seconds.
  - The call between C and D, which had a duration of 15 seconds.

And here is where the problems arise, because only the a-leg (from A to
FS) contains the proper value of <billsec> for the "logical" call
between A and B.  The CDR of the FS to C channel has a <billsec> of 30
seconds and the one for the FS to D channel has 15 seconds (all aprox).

However, all CDRs appear to have the same <call_uuid> so they can be
easily related.  The problem is that we would like to avoid this CDR
dependency if we can, mainly because the background process that treats
with CDR information is stateless at the moment.

The purpose of this message is to survey about what other people is
doing about this, as it seems to be the source of some headaches
according to the list archives.  I think that, in the end, we will have
to mix up different CDRs but we may be missing some hidden functionality
of FreeSWITCH.

Thank you for your time :-)

P.S: Testing the same call flow, but with attended transfers it is even
more complex in terms of CDR processing, but we would like to have some
idea on how to solve this one first.

-- 
Isaac Jurado
Internet Busines Solutions eConcept