[asterisk-users] Asterisk's DANGEROUS Transfer CDR's

[Grey Man]

Hi All,

PLEASE READ if you depend on Asterisk CDR's and support transfers.

Apologies for the shout but I'm desperate to get others to agree Asterisk has a
big problem with the CDR's that are generated for transfers. I can understand
why not too many people are interested as transfers are complicated and
messy. However for those of us having to support transfers and depending on 
Asterisk CDR's for our billing we are in a sticky predicament! For anyone
using Asterisk in a provider environment unaware of any problem I urge you to
do a simple blind transfer on your system and check your CDR's. Most Asterisk
based providers I tested are blocking transfers but I did find some other
providers out there missing billable call legs!

My goal is to try and get acknowledgement that there is a serious problem 
here that warrants a re-think about how Asterisk CDR's are generated.

In an effort to succinctly encapsulate the problem I've produced the call and CDR
flows below. Hopefully they make sense but if not I'm more than happy to elaborate
and share my test results (the flows below won't be legibile without a mono spaced
font, copy and pasting into notepad will make them readable).

Blind Transfer (1.2 and 1.4):

Time           Calls                CDRs
                             | Dest  | Dur(s) |  
                             |-------|--------|
 T0 -| Alice --> * --> Bob   |       |        | 
     |                       |       |        |  
 Tt -| Carol <-- * --> Bob  -|  Bob  |   Tt   | 
     |                       |       |        |
 Te -| End                  -| Carol |   Te   | 


Attended Transfer (1.2):

Time           Calls                CDRs
                             | Dest  | Dur(s) | 
                             |-------|--------|
 T0 -| Alice --> * --> Bob   |       |        | 
     |                       |       |        |  
 T1 -| Alice --> * --> Carol |       |        | 
     |                       |       |        |
 Tt -| Carol <-- * --> Bob  -| Bob   |   Tt   |
     |                       | Carol | Tt - T1|
     |                       |   s   |   Tt   |
     |                       |       |        |
 Te -| End                  -|   s   |   Te   | 


Attended Transfer (1.4):

Time           Calls                CDRs
                             | Dest  | Dur(s) | 
                             |-------|--------|
 T0 -| Alice --> * --> Bob   |       |        | 
     |                       |       |        |  
 T1 -| Alice --> * --> Carol |       |        | 
     |                       |       |        |
 Tt -| Carol <-- * --> Bob  -|       |        |
     |                       |       |        |
 Te -| End                  -|  Bob  |   Te   | 
                             |  Bob  | Te - T1|

To put it another way here are some examples of how Asterisk systems and 
transfers can be exploited.

1. Place a call to a mobile you plan on having a lengthy call to. As soon as the
call is establised blind transfer it to a low or free cost destination. You will
only be billed for the mobile call up to the time it takes you to do the transfer
the remainder of the call will be billed at the low cost or free destination.

2. With Asterisk 1.4 place a call to two billable destinations and then transfer
them together. You'll only be billed for each destination up until the time it takes
you to transfer.

3. With Asterisk 1.2 place a call to a low cost or free destination. Then place a
call to an expensive destination and do an attended transfer. You'll only be 
billed for the expensive destination up unitl the time it takes to do the transfer.

I have opened a bug on the issue but I suspect without input from others having
the same problem it will fade away.
http://bugs.digium.com/view.php?id=11849

From my point of view the design solution to this problem would be as simple
as changing the CDR generation from one CDR per bridge to generating a CDR
for each end of a bridge. When the end of a bridge changes or the bridge is
hungup a CDR(s) would be generated.  The implementation would 
undoubtedly be a lot more difficult but if the design could be agreed upon at
least those of us in between a rock and a hard place on this could decide 
to sponsor development, offer a bounty etc.

Regards,

Greyman.
 



      Make the switch to the world's best email. Get the new Yahoo!7 Mail now. www.yahoo7.com.au/worldsbestemail