When deploying Remote Phones, whether as a Carrier in a hosted solution or as an Enterprise with home or remote employees, these phones will have to reside behind some type of firewall. Firewalls are meant to provide security by hiding the private network addresses of end user devices and at the same time preventing all unsolicited network traffic from entering the private network. In addition, VoIP uses SIP (RFC 3261) as a communications protocol, which is an application and not a network routing protocol, and firewalls don’t provide application support.
Making a phone call by its very act is an unsolicited event, an event that every firewall will block or deny traffic. Or in some circumstances, poking holes in the firewall to allow these phone calls through simply causes more security and audio problems.
The SBC provides several features to enhance the deployment of VoIP. It works with near end deployed firewalls by accepting the VoIP traffic and applying security and routing policies to the phone calls. In addition, providing Far End NAT solutions for SIP phones deployed behind firewalls that are across the Internet.
|Download this printable PDF Cheat Sheet for your reference on the powerful capabilities and features of the Session Border Controller.|