[Users] Accounting using dialog and sst module

Ron Winacott ronw at somanetworks.com
Tue Jan 2 15:21:57 CET 2007

On Tuesday 02 January 2007 9:00 am, Asterisk Expert wrote:
> Hello Ron,
> Thanks for your response. Now I'm able to start and destroy dialog
> properly. But I guess dialog timer is reset when openser receives "Update"
> message. I looked in dialog and sst module codes and found that they rely
> on UA to send "Update" message periodically to keep the dialog active. I
> dont think it is good idea to rely on clients as all clients may not be
> sending "UPDATE" messages after call is established. Correct me if I'm
> wrong. Also I think that I may have to change source code of dialog or sst
> to send bye if any UA is broken and can't send "Bye" in case of dialog
> timeout.

But waiting and acting on UPDATE/re-INVITE is what SST (RFC-4028) is all 
about. The SST module is an implementation of the RFC for a SIP proxy. One of 
the clients in the dialog must support timers (SST) and the module will 
figure out who does and request SST timers (UPDATE/RE-INVITE) from that UAC 
if nether UAC want to use timers.

As for the proxy sending a BYE on a timed out SST/dialog, this is against the 
RFC. A proxy can't inject a SIP message into the conversation like that. 
Also, there is the technical issue that nether the SST or dialog module 
track/save enough information (as far as routing goes) to send the BYE. 

The SST module is for statefull proxy servers to allow them to free up locally 
held resources when a dialog times out without having a default dialog time 
out value of 24 hours, and causing one of the UAC's to "ping" the signal path 
to let everyone on it know the conversation is still on.

Without one side supporting timers (SST) I would suggest you do not use SST 
for any kind of accounting information because as per the RFC, one side must 
support timers/SST for it to work. 


Ron Winacott - SOMA Networks, Inc.
Work: 1-416-348-1580 - ronw at somanetworks.com

Programming today is a race between software engineers striving to build
bigger and better idiot-proof programs, and the Universe trying to produce
bigger and better idiots. So far, the Universe is winning
 - Unknown

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