As written many time in this mailing list it depends on what services you want to provide using such "voice servers". If they are transparent media relays then rtpproxy or mediaproxy(-ng) can help. Also you can integrate it with your billing to authorize calls and limit their duration.

Though if you want to provide voicemail, call recording, transcoding, etc.. you have to use software like asterisk or freeswitch.
Hello, I have a question about the load balancing module of kamailio.
As the site http://kb.asipto.com/ say, Kamailio is as a SIP proxy router to scale Asterisk.
 
Can I run a kamailio instance as load balancer, and other several instances as voice server replace of Asterisk?
 
If I can do that, could you give me a tutorial? We are using kamailio as our server. Thank you very much.


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