When it comes to ensuring quality of service and security for enterprise VoIP, session border controllers are becoming increasingly important. As this Network World test of SBCs explains, a session border controller is a traffic cop that facilitates and mediates VoIP flows in real time, in both directions between private VoIP domains, an enterprise and a VoIP-based service provider, or two service providers. Covergence recently announced "the industry's first SBC delivered as a virtual appliance," according to Rod Hodgman, vice president of marketing at the company.

The virtual appliance, called a CVA-50 is targeted at enterprise branch offices in both private networks and for service providers in the small and midsize businesses market. The software comes as as a pre-built, pre-configured, ready-to-run enterprise application, packaged with an operating system inside a virtual machine and is designed to run on any x86-hardware. The list price for CVA-50 is $5,000.

The virtual model adds to an existing portfolio of other hardware-included SBCs that are delivered with the appliance, or as software that runs on a blade (a single board computer) in either the AdvancedTCA chassis or the IBM BladeCenter chassis. Covergence has demonstrated interoperability with a wide range of other VoIP IP-PBX hardware and software provided by other vendors like Avaya, Acme Packet, Broadsoft, Cisco, and Microsoft.

Covergence was established in late 2003, and the company is focused on extending a traditional SBC to define, enforce, and audit fine-grained security, control, routing, monitoring, and interoperability policies on VoIP, video, IM, presence, and other real-time services.

Our comments: We’ve seen a debate in the industry about where SBC functionality belongs including advocates for session border control in stand-alone SBC appliances, inside the IP-PBX, inside the core and edge routers, and now with software running on an x86-hardware platform. We believe that it isn’t so much where the SBC resides as the fact that SBC is necessary for VoIP and unified communication solutions that extend to other locations and connect to other networks. In fact, we think the best alternative is to have some degree of SBC in every device that participates in VoIP and UC delivery. If you agree (or if you don’t) please feel free to e-mail us or add your comments into the comments box below.

Steve Taylor is president of Distributed Networking Associates and publisher/editor-in-chief of Webtorials. Larry Hettick is a principal analyst at Current Analysis.