ViDe Videoconferencing Cookbook
Why are Standards, Openness, and
H.323 is an International Telecommunications Union (ITU) standard for videoconferencing
over IP. It is an umbrella standard that specifies mandatory and optional requirements
in several areas to enable a complete "call" or communication sequence. The
standard also defines several major components that may be part of the call
- terminals and clients, gateways, gatekeepers and registries, multi-point
control units, and now secure directory services. The reason for the standard
is to enable interoperability between different vendors' implementations
of these components. As is the case with all standards, there is a danger of
either over-specification or under-specification. If the standard is over-specified,
it may become difficult to implement in the form of a cost-effective product.
If the standard is under-specified, there may be room for different interpretations
that lead to equally compliant yet non-interoperable implementations. Version
1.0 of the H.323 specification left significant latitude for vendor interpretation.
This latitude enabled wide differentiation in the marketplace but led to poor
interoperability among early products. Subsequent versions of the standard
addressed this issue by becoming more specific in key areas and interoperability
between H.323 vendor implementations seems to work well. But with the move
toward the newer SIP protocol draft recommendation, we find ourselves again
in the situation with little or no interoperability between vendor offerings.
Fortunately, market forces have resulted in several strategic partnerships
among videoconferencing vendors, which will tend to increase interoperability
in this arena. In some cases vendors have sought to acquire complementary products
in order to offer complete "turnkey" solutions. In others, joint ventures have
been formed to assure interoperability within a broader product line.
Most of this cookbook is devoted to standards based videoconferencing, primarily
H.323 with movement toward SIP. Mention is made of other proprietary solutions,
some of which can interoperate with standards based technologies. Nonetheless,
ViDe continues to remain focused on and an advocate for standards-based solutions.