What is the difference between a proxy server and B2BUA when it comes to SIP? How can I decide which one I should go for?
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I believe the Back-to-Back User Agent (B2BUA) server is generally used for delivery of advanced features requiring stronger and more intelligent resources than that of proxy servers. I think there are many hybrid arrangements involving use of both, but it's also important to understand the network requirements and company investment resources immediate and longer term. Radvision has an excellent white paper here.
For customers building in value-add solutions, generally speaking, you will look to B2BUA -- but the reality is there's always a hook with pre-existing requirements or budget constraints and the solution ends up being hybrid. Pay close attention to the key differences of the two in Radvision's white paper, page 7, Table 1. Short term, I think many customers are using Proxy but they need to look ahead to a more robust solution and that is going to be B2BUA especially when they integrate mobile phones with the office systems and applications or web applications with click to dial.
This was first published in November 2009