Regular readers of this column will be familiar with my view that when it comes to IP telephony implementations, the devil's in the details. It's time to take a look at some of the critical operational issues.Regular readers of this column will be familiar with my view that when it comes to\u00a0IP telephony\u00a0implementations, the devil's in the details. Last fall, we talked about\u00a0how to craft a credible cost-justification\u00a0(hint: If you're hoping to justify IP telephony based solely on WAN cost savings, you might be in for a rough ride). Now it's time to take a look at some of the critical operational issues.Many of these observations come from an excellent birds-of-a-feather session I attended at the recent VoiceCon conference in Washington, D.C. If you're interested in IP telephony, there's no better conference. Next year's is in Orlando - check out the\u00a0Web site.The best part of this session was the comments from end users. (It's amazing what you can learn when the "experts" shut up and let the users talk). Lessons learned include:Don't neglect quality of service (QoS). IT executives at several large companies stressed the value of taking the time to perform a QoS assessment upfront.Start by benchmarking your existing network performance (I gave some pointers for doing so in\u00a0last week's column).Then put in place a framework for implementing QoS. Decide where the packets are going to be marked and how the network will process them.Test your scenario exhaustively before deployment. Approaches that work perfectly on paper might fail to perform in a real network.And most importantly: If you're just beginning to consider an IP telephony implementation, make sure you budget for the QoS assessment piece. Several folks commented about the difficulties they'd had in getting their organizations to agree to spend time and money on the QoS assessment.Plan for power. One of the biggest concerns expressed had to do with ensuring uninterruptible power to the IP telephony infrastructure. This is harder than it sounds.Sure, installing uninterruptible power supplies and back-up batteries is a no-brainer - but have you thought about deploying a management and monitoring system for the power elements? How often will you be replacing batteries, and at what cost? Several folks reported that because of form-factor changes and upgrades, they needed to completely replace batteries and power supplies every two to three years.Whether you do this yourself or outsource the service, it's a significant cost, so be prepared.Set a support strategy. As we've discussed previously, service and support can be the Achilles' heel of an IP telephony deployment, particularly when it comes to value-added resellers (VAR) and systems integrators.Look for VARs that have a strong relationship with your primary equipment vendor. Also note that the quality of a systems integrator tends to vary by geography - one that performs phenomenally in Illinois might do a poor job in Idaho.Finally, recognize that all consultants and engineers are not created equal. Ask your VAR to provide bios of specific support engineers - and commit to dedicating the particular individuals you like to your project.