On the network side, I've seen many companies do voice and video using their own VPN over IP network services from carriers like AT&T, WorldCom, Sprint and Qwest. These private IP networks have so much extra capacity right now (what some have called a fiber glut) that video and voice performance is outstanding, even without special QoS systems. In fact, if you simply purchase basic Internet services from the same carrier at each location, your traffic will stay on the carrier's private IP network the whole time. So you get all the benefits of a high-performance private network without the cost of service level agreements and special services.
Finally, new VPN gateways can further encapsulate IPsec packets inside TCP or UDP packets. This allows firewall traversal at either end without problems, so you can set up your VPN gateways without changing out your firewall or getting new publicly routable addresses from your ISP. The one caveat I need to throw in here is regarding network address translation (NAT). Some collaboration software and voice/video software requires each participant to have a publicly routable address that is not NAT'ed because the protocol uses the address at the application level. If your conferencing or video software requires this, you may need to make adjustments to your network to accommodate it.
All the best,
This was first published in June 2002