When implementing video conferencing capabilty many businesses are more focused on the make-up of the video suite itself.....and assume that DSL bandwidth is sufficient for their network backbone. Whether this be an existing network or intended new install.....assuming that DSL is sufficient to support your requirements may be shortsighted. Beware, there's more out there to consider.

Before "jumping to conclusions" it's important to consider all of your options....and how each may best (or not) support your video conferencing needs.

xDSL technologies are usually deployed as “over subscribed” packet switched networks. By oversubscribed I mean that during those brief periods when the two end points are not transmitting the bandwidth to carry data from other users. In these networks the bandwidth used by connections between two ends points has the characteristics of variable bandwidth and variable delay. The resulting jitter can be very problematic for video circuits. However, xDSL technologies are usually much less expensive than ISDN/T carriers.

The "A" in ADSL stands for "asymmetrical". SDSL, and usually VHSDL and HDSL, are symmetrical.

If your videoconferencing is two-way, you need symmetry, or the performance will be horrible on the low-speed side. A caveat: if your video codec gives sufficiently good compression that the low-speed side gives enough bandwidth, you may be all right.

You also have to check the service guarantee on DSL, Frame Relay, and even Metro Ethernet. Do they give you either constant bit rate (CBR) or near-real-time Variable Bit Rate (nr6VBR), which are generally considered necessary for full-motion video quality? Note that CBR and nrtVBR are possible through IP connections that guarantee quality of service, which usually will mean contracting for a VPN.

You really want symmetry with your video conferencing. The cheap consumer class aDSL products are great when the downstream bandwidth is significantly greater then upstream, but in video/teleconferencing, the needs are both up and downstream.

If video conferencing is something you would use regularly, and count on for your business, then go for a real SDSL line or a T1 (or a DS3 for larger businesses with frequent usage.....especially with large numbers of participants, participating locations, or excessive distant). There are vendors that can offer these at competitive costs and give business class service and support.

Many businesses are abandoning DSL in favor of Sprint's EVDO rev A implementation of CDMA. You'll find some carrier agnostic info at EVDOForum.com which cites rev A speeds as EVDO Rev A 450Kbps-800Kbps Download, bursts to 3.0Mbps, and 300Kbps-400Kbps Upload Speed, bursts to 1.8Mbps. Sprint is now confident that these are very conservative numbers. While your own mileage may vary.... some routinely get faster speeds than this. Sprint expects to have more than 190 Million EVDO Rev A POPs by the end of April (we'll see though).

If your business is small, the underlying technology for video should be IPTV with any of the web-conferencing agents. The video streams would be routed via DSL service. If you're served by cable TV, you may prefer cable internet to DSL-based internet, but cable carriers often do not serve industrial areas. Thus as a business cable may not be available to you.

If your business has a full Private Branch Exchange (PBX) system for your telephones, you probably already get ISDN service from your phone company. ISDN permits "dynamic allocation" of channels which dedicates throughput to video when it is needed and makes the same capacity available for other applications, such as voice or data, when it is needed there. There are lots of vendors who support/supply ISDN-based video conferencing equipment.