16. - SIP and B2BUA Back to Back User Agent

• Back-2-Back

Thee B2BUA its a standalone proxy when it receives a request process the request just as thee intended destination UA Server would, it repackage the request and act as a UA client then generates a new request and send this to the destination, the B2BUA will maintain the complete call state and continue to send request and responses on which its involved, in essence it own the session.

A B2BUA implementation would make it easier to offer the following, you just have to choose your B2BUA carefully

• Centralized management of all calls.
• PBX call management features such as call transfer, forwarding and automatic call disconnection to warm a user that credit is low.
• Billing functionality.
• Call Conferencing facilities.
• The ability to 'hide' the network such as Private IP address schemes and the underlying network topology from scanning attempts.
• The ability to connect two different types of signaling networks such as SIP and H.323 for co-existence during a migration to a fully SIP based network.
• Implement and enforce policies such as 'Class of Service and Restriction'.
• Manage Security and NAT issues.