Q1: What percentage of your VTC installs are IP vs. ISDN?

A1: I would say that 95% of the current VTC installs are ISDN only. The remaining 5% are IP only, or IP and ISDN combinations using a Gateway device. However, some clients who are implementing ISDN-only right now are specifying the installation of equipment that will seamlessly support both ISDN and IP (in the future), without additional cost. So, even though the near-term option is ISDN, an increasing number of clients are thinking IP and are clearly planning to go in that direction eventually.

Q2: What's the advantage of IP over ISDN?

The primary advantage of using an IP-based network is cost management. Clients who have purchased dedicated network bandwidth know what their costs are going to be on a month-to-month basis. Theoretically, they could be using their videoconferencing systems 24/7 over their dedicated network without incurring additional usage costs. ISDN is usage-based, and frequent users can rack up significant network charges. This is exponentially increased for international usage. A cost-benefit analysis should be done in
the system planning stages to project anticipated usage and ISDN network costs vs. cost of dedicated network.

Another benefit is quality of service. ISDN is a public-switched digital-network, which can be routed through Telcos [telephone companies] in a number of different ways - and in my experience, is sometimes subject to potential congestion and quality issues. A dedicated internal intranet/VPN essentially guarantees that the network is 'clean' and available from one end to the other.
Important Note - this only applies to internal intranets/VPNs and dedicated internal networks. Many clients believe that the public Internet is 'ready for video.' It isn't. There are [still] serious quality issues currently associated with doing business-quality video conferencing (128kbs+) over the public network. In my experience, service can be unreliable, and there are frequent disruptive audio 'hits' that remind one of the old 'Max Headroom' show.

Lastly, another advantage of doing video over IP is speed. For those clients looking for IP/ISDN video conferencing, they can invest in a lower-cost system which supports lower ISDN line speeds, but still can 'cook' at 768kbps over IP. Systems exist that can support up to 2Mbps over an Ethernet network. Easy-to-use Desktop video is now a reality at 384kbps over Ethernet.

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