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.
Then there are the hidden costs of VoIP. They're all about options and licenses, and the expense can be substantial. Many standard PBX features, such as E911 (Emergency 911) service support, are optional with VoIP. Cisco's E911 server application, for instance, lists as a $5,999 option. This gets you 100 licenses, meaning 100 extensions can be part of the E911 service. Each additional license is $10, without volume discounts. It would have cost us more than $50,000 (in addition to the cost of the core VoIP components) to equip the entire Syracuse campus with E911 service.
And beware of additional hardware resource costs sneaking up on your budget. Case in point: Call Manager is responsible for call processing, database processing and management and other tasks, so there's only so much processor power to go around when it's time to place calls on hold or when multiple conference calls are under way. Call Manager's limited on-board DSP (Digital Signal Processing) resources handle conference calls and other advanced system functions. DSP performance is crucial at Syracuse because we have a large volume of outside calls: In the pilot, we found that when around 200 or more extensions were in use simultaneously with a lot of call conferencing and hold conditions taking place, the DSPs could get overtaxed. The only solution is to buy hardware. For a campuswide system, we would need multiple $19,000 add-in boards for our core switches to get more DSP power.
You may incur other unforeseen costs for your new VoIP environment that your vendor doesn't advertise, so hammer your sales engineer for details on the possibilities--especially if your network is growing.
History Lessons
If your IT group hasn't had to worry about QoS before, it will with VoIP. Voice traffic may not be bandwidth-heavy, but it is highly sensitive to latency, jitter and delays. Make sure you budget for VoIP-specific QoS training if these kinds of Layer 2 and Layer 3 QoS issues are new to you, as they were to us at Syracuse. That way, you can configure your network so voice gets top priority.
Don't be shy about asking for outside help. Shelving the PBX and putting hundreds or thousands of calls across the network can be a daunting task, and few IT departments have the staff count and specialized talent to make the switch exclusively with in-house resources. Ask your VoIP vendor for integrator recommendations. Once you select an integrator, tell that person you want to know up front all the costs of implementing VoIP, and that your goal is to have minimal impact on users during the transition. At Syracuse, we handled our pilot project rollout in-house, but if we deploy VoIP across campus, we'll probably use an integrator to supplement our in-house skills.
It's worth looking into the history of outside contractors before you sign on the dotted line, too. VoIP is new enough that many consultants are still learning the ropes. The last thing you need is a green consultant using your deployment as a VoIP training ground so he can make a name for himself. Make sure you know your integrator's specific areas of expertise. There's a big difference between implementing an IP call-processing server and actually setting up a complex IP call-center application.
Although few midsize to large enterprises have made the jump to VoIP pilots or production systems, it's still the likely future of voice. Start studying, planning and upgrading your network now. That's the best way to prepare for deploying VoIP when the time is right.
Lee Badman is a network engineer at Syracuse University. Write to him at lhbadman@syr.edu.
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