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Rich Tehrani

[April 29, 2004]

Sidebar: Q&A With Santa Cruz Networks



Editor's Note: This is the eleventh in a series of short articles from Rich Tehrani based on recent visits with a number of VoIP vendors. The previous article is available here.

Back to main article: Breakthrough! Videoconferencing Over 20 Kbps

I had some technical questions about this product and I decided it was better to post my questions and the answers from Santa Cruz Networks directly without editing. Hopefully this will help those of you with additional questions. If not, please post a question in the TMC forums.

Q: You mentioned that you use TCP instead of UDP.

A: Our goal is to offer the most reliable and secure form of communication that works in the real world on all networks with a minimum of setup and/or IT intervention. As such, all Santa Cruz Networks data streams (voice, video, IM, app sharing, etc.) are sent using TCP via a client-server architecture with full 128-bit SSL encryption. This data goes through outbound TCP Port 443, the standard SSL port. Usually the IT staff needs to do nothing as this port is open by default on most all firewalls. For added security, all communications are initiated from the client within the firewall, meaning that the port only needs to be open for outbound traffic only.

Q: Are you the only ones doing this as far as you know? In my research, it seemed that the older SIP standard also used TCP. Is this correct? Any elaboration is appreciated.

A: TCP is used by other companies for transporting media, however, our method of using TCP is quite unique. We�ve built a transport protocol on top of TCP that uses a managed pool of TCP connections. You can think of it as a �spread-spectrum� approach, but applied to TCP. Our methodology allows us to be low latency, high bandwidth and lossless. We also work on any type of Internet connection, 28K through T1.

SIP (Session Initiation Protocol) is just a handshaking mechanism between two devices, not a communications protocol. While it uses TCP, it often connects two devices that will communicate over UDP channels, which usually requires extensive IT intervention to get the solution to work.

Q: Doesn�t TCP increase overhead dramatically?

A: The overhead is actually quite minimal -- the way in which we use TCP -- and since it allows us to achieve lossless transmission, you could argue that the benefit clearly outweighs the cost. Furthermore, our multiplexing more than counteracts the additional overhead imposed by TCP. For most RTC solutions, audio, video and document data are sent separately -- each with its own associated packet overhead. By multiplexing, we greatly reduce packet overhead.

Q: If TCP is so great, why isn't the whole industry using it?

A: Our methodology is quite unique -- the fact that the industry isn�t using it is simply a testament to that fact. True, RTC over TCP is a hard problem to solve -- it took us four years of constant focused effort to solve it. Our patent-pending spread-spectrum solution and sequencing technology give us a great advantage over other solutions in the industry that would choose to use TCP.

Q: You mentioned that you send the same segment of voice over multiple TCP packets. Doesn�t this make quality worse in a low bandwidth situation?

A: Our audio redundancy feature greatly reduces audio drop-outs -- however, we never exceed the amount of bandwidth that�s available on the user�s connection.

Please talk back to me in our forums

Rich Tehrani is TMC's president. He welcomes your comments. Participate in our forums.

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