Matt,
Because SER handles SIP messages, not RTP streams, it cannot 100% accurately record CDRs. For instance, if the BYE message is lost because a client crashed, SER has no way of knowing when the call ended or how much it cost. A BTBUA gets round this problem by having the RTP packets come to it, so if a client crashes, the RTP stream stops and the BTBUA knows the call has finished. The disadvantage of a BTBUA is that it adds latency and doesn't scale well, because it needs to handle all the RTP traffic.
I install quite a few SER and Asterisk systems for my customers, and a fix for this issue is the most frequent item I'm asked for. It's unavoidable, however, if one wants SER's scalability. What I usually recommend for them is to install a SER system (for scalability, registrations, routing of calls that don't need a CDR, etc) fronting multiple BTBUAs such as Asterisk or Cisco (for accurate billing of PSTN calls).
Alistair Cunningham, Integrics Ltd, Telephony, Database, Unix consulting worldwide +44 (0)7870 699 479 http://integrics.com/
matt morris wrote:
Hello List,
Just wondering, what is the radius account module for SER not able to do, that would require the use of B2BUA in terms of having a CDR? Forgive me if it is a dumb question...
Thanks.
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