I think in this case when 5k call are involved i think all the difficulty of the project is to split the load on different parts of the system. In my case i would do it like that:<br><br><br>Phones --->Opensips (Double server with heartbeat and in different places)<br>
....................|<br>....................|<br>..............asterisk 1-n (mainly for voicemail)<br><br><br>Opensips should easily handle you registrations and calls, you just need the LCR module for outgoing and dbalias for incoming. If you need the 100% exact and accurate CDR you should consider mediaproxy, the advantage of mediaproxy is that it is capable if detecting if there is no more udp traffic and send BYE packet, the disadvantage is considerable, the traffic is going through your system, many mediaproxy servers are advised in this case, also they need to be installed in strategic points (close to clients). I would let asterisk to do it's part of voicemail server only. Opensips is a great tool, look at their site, also look at cdrtool and mediaproxy. I hope my post helped.<br>
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