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
Back to main article: Breakthrough! Videoconferencing Over 20
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
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.
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.
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.
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
Please talk back to
me in our forums
Rich Tehrani is TMC's president. He welcomes your comments.
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