If your remote sites use different support applications from those your main location uses for voice-call accounting or helpdesk functions, be careful when you install your VoIP system in all sites. Different call-accounting and helpdesk functions can cause Excedrin headaches. Take inventory of your support software suites (and their dependencies and operational rules) so you can ask vendors and integrators what percentage of your existing network operations will work with VoIP and how much will need to be overhauled.
Depending on the size of your enterprise and the number of telephone extensions, you'll probably need to renumber some or all of your voice extensions. At Syracuse, going VoIP campuswide would require renumbering thousands of telephone lines. Each VoIP extension in Cisco's AVVID is a network device, so each IP telephone requires an IP address, too. That would entail adding thousands of new devices onto the network. And because of some limitations to our existing DHCP setup, accommodating these additional IP nodes would require a complete overhaul of our DHCP infrastructure.
Expect to add more servers with VoIP, too. As the Syracuse pilot progressed, we found that VoIP services, such as XML and call-center applications, typically require their own servers. We installed a separate server for the flashy XML applications we used for viewing the weather forecast and corporate directory on display screens on the VoIP handsets. We considered other high-end VoIP services, such as an IP call center, but even for our relatively small group of IP call-center users, it would have cost about $100,000, including at least four new servers.
With Cisco's AVVID Call Manager application, meanwhile, users enter login IDs rather than access codes for long-distance calls, a model that doesn't match our billing system. We identified a third-party call-accounting application that was a better fit, but it requires a separate server. So, in the pilot, we restricted the users to "trusted" IT staff members to avoid the call-accounting issues at the university. Their calls weren't tracked.
With all the additional Microsoft Windows 2000 and SQL 7 servers running VoIP applications, you'll have to deal with their administration, patches, licenses, upgrades, maintenance contracts and device security. At Syracuse, we always had four to eight servers running. Because VoIP blurs the lines between network and application, we weren't sure how to divvy up the work between the network and the server folks.
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