Among the "WAN tips for 2004" offered by consultant Jim Metzler of Ashton, Metzler & Associates at last week's ComNet show in Washington, D.C., were some words to the wise about deploying VoIP.

Carefully scrutinize the spate of voice over VPN service announcements that are coming, Metzler advised. At a minimum, he said, there should be meaningful service-level agreements associated with these offerings (emphasis on the word "meaningful"). He advises in particular to pay attention to how each service provider measures one-way delay.

The "truly paranoid, experienced users" he said, might want to drill down into exactly how the VPN providers plan, technically, to transport voice traffic with high levels of quality and reliability.

Metzler also advised that, before deploying, you assess your WAN's level of "readiness" to support VoIP (and other delay-sensitive applications). Among the requirements:

* End-to-end quality of service that is relatively easy to set up and manage.
* Tools and processes for end-to-end monitoring and measuring jitter and packet loss.
* A way to not only measure delay but to troubleshoot sources of delay.
* Consistent, very high levels of network availability.

He also warned that you might need to look deeper than the obvious to figure out what you are actually paying for voice communications. Offhanded comments that voice costs 2 to 3 cents per minute, he said, usually ignore the following expenses, which must be figured in to the total VoIP cost:

* T-1 access lines.
* Switched access.
* PBX hardware, software, and maintenance.
* Personnel costs associated with voice.

Steve Taylor is president of Distributed Networking Associates and publisher/editor-in-chief of Webtorials. Jim Metzler is vice president of Ashton, Metzler & Associates.