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ProShare(TM) Video: TCP/IP Requirements
Contents:
PROSHARE VIDEO SYSTEM TCP/IP REQUIREMENTS
INTRODUCTION
The ProShare Conferencing Video System provides video conferencing using
existing LAN infrastructure and standard LAN communication protocols:
Novell* NetWare* IPX, TCP/IP, and NetBIOS. The TCP/IP protocol is
available from many vendors and has a standard application interface
known as WinSock. Unfortunately, the WinSock interface can't
consistently meet the real time requirements of video conferencing. In
addition to WinSock, many vendors provide proprietary interfaces. For
rel1.8, the ProShare Video System supports TCP/IP from two vendors using
their proprietary interfaces. Over the next year, Intel will be working
with communications vendors to encourage more of them to provide the
real time support required for video conferencing. In the long term,
Intel is working with Microsoft*, Novell, and others on the definition
of WinSock II. This new interface standard will be suitable for video
conferencing, allowing ProShare Video Systems to provide
vendor-independent TCP/IP connections.
THE WINSOCK APPLICATION INTERFACE
Many vendors support the TCP/IP protocol, and interoperability between
two systems using TCP/IP is usually a given, even if different vendors
supplied the communications stacks. A standard, vendor-independent,
application interface known as WinSock makes this interoperability
possible.
Unfortunately, WinSock can't consistently meet the real-time
requirements of ProShare video conferencing. Using WinSock,
applications transfer data to and from the communications stack using
Windows* messages. When the communications stack receives data from the
network, WinSock sends a Windows message to the appropriate application.
If that application isn't currently executing, it won't see the message
immediately. In general, with several applications running in Windows,
it could be a long time before the application receives the message from
the communications stack. The same problem occurs with data flow from
the application to the network. When an application has data to send to
the network, it notifies the communications stack by sending a Windows
message. Again, the message might take a long time to get to the
communications stack.
Much of the power of ProShare video conferencing comes from being able
to share applications, use a shared notebook, or transfer files while
talking with and viewing the other person. The user can also be running
other applications at the same time. Some applications, originally
written for the single-tasking DOS environment, monopolize system
resources. In this multi-tasking environment, the timely flow of
messages across the WinSock interface can be disrupted. This problem is
compounded by the fact that Windows does not offer pre-emptive
scheduling of tasks. For example, if the ProShare application used the
WinSock interface, audio or video streams could be lost while the user
held a mouse button down in a word processing application.
PROPRIETARY APPLICATION INTERFACES
Fortunately, many vendors support proprietary interfaces to their
communications stacks, in addition to WinSock. These interfaces provide
an alternative to the Windows message protocol for transfering data.
When the communications stack has data ready for the application, the
stack can transfer the data immediately. The stack can also receive
data from the application immediately when the application has data
ready to send.
In Q2 '94, the design team evaluated the proprietary interfaces of
TCP/IP stacks from seven vendors. At that time, only the Novell and FTP
stacks met the real time requirements for audio, video, and data
conferencing. Only these stacks allow rel1.8 to support the TCP/IP
standard without sacrificing audio and video quality during a ProShare
video conference.
BUT... MY FAVORITE VENDOR ISN'T SUPPORTED!
There will be cases where the ProShare application doesn't support the
TCP/IP vendor currently being used by a customer. In these cases,
customers will need to change the communications stack on their ProShare
systems to one of the stacks supported in rel1.8. There may be issues
with corporate IT standards, but most existing TCP applications use the
vendor-independent WinSock interface and will run, without
modifications, on either of the stacks rel1.8 supports. A serious
problem does arise if the customer has an existing application that is
using the proprietary interface on a communications stack that rel1.8
does not support. In that case, the customer can't run both the
ProShare application and the existing application simultaneously because
only one TCP stack can be active. The biggest problem here is that the
customer may be unaware that the existing application is dependent on a
particular stack. When the customer changes communications stacks, an
old application might unexpectedly fail to run.
WE'RE WORKING ON MORE TCP/IP SOLUTIONS
Over the next year, Intel will be working with communications vendors to
encourage more of them to provide the real time support required for
video conferencing. It is Intel's intent to include more TCP/IP vendors
on our supported vendor list with later releases of the ProShare Video
System.
Intel is also working with Microsoft, Novell, and others on the
definition of WinSock II, the next generation of the WinSock interface.
This new interface standard will be suitable for video conferencing,
allowing ProShare Video Systems to provide vendor independent TCP/IP
connections.
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