6 Mar
2005
6 Mar
'05
11:58 p.m.
Alistair Cunningham wrote:
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.
This is not necessarily true. SIP permits building signalling-only
B2BUA, which if designed correctly will be able to handle up to 50-100
call setups/teardowns per second on any modern x86 hardware. This will
provide capacity sufficient for any mid-level ITSP - allowing to bill
more than 10 millions per month. If this is not sufficient then several
of such B2BUA can be installed in parallel to provide more scalable
solution. The problem with using either Cisco or Asterisk as SIP B2BUA
is that they handle both signalling (SIP) and media (RTP), which makes
them less scalable and introduces the problem with increased latency,
losses and jitter.
Regards,
Maxim
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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