Today’s telecommunications networks are a delicate blend of clients and servers that together offer virtually endless possibilities when it comes to services and applications. For every new client developed, there seems to be a score more on the way — from mobile handsets, PDAs, terminals, telephones, video phones, IP set-top-boxes, and so on.
There are essentially two types of servers that connect between clients on large networks: Proxy servers and Back-to-Back User Agent (B2BUA) servers. The more prevalent Proxy servers feature predictable behavior — simply connecting between clients. Effectively, B2BUA servers are much stronger and intelligent entities that perform actions which Proxy servers cannot. Moreover, B2BUA servers provide a flexible solution for a wide range of applications and services and are becoming the primary engine for more and more SIP servers in NGN and IMS networks.
The difference between Proxy servers and B2BUA servers is sometimes not fully understood. In this article, we will explore what makes B2BUA servers such an appealing alternative to standard Proxy servers. Better understanding of B2BUA servers can help managers understand the value, and the tradeoffs, of choosing a B2BUA server, as well as the frameworks needed to develop a wide range of SIP applications and SIP services using it.
