Here are five questions that you should answer before deciding on the appropriate system for your enterprise.
Can you really get rid of all of your analog phone lines? If you have alarm systems, front door sensors, fax machines, or other things that require analog phone lines to communicate with the outside world, then you will have to maintain some sort of mixed VoIP/analog system to support these connections. Most of the major PBX vendors have ways to do this, fortunately, by adding analog expansion cards or in some cases line converters.
Do you have a spare Ethernet pair to connect VoIP phones in all of your offices? If you designed your office wiring about ten years ago, you probably thought you were doing the right thing by pulling CAT 6 wiring to each desktop and leaving it at that. If you pulled multiple runs, then you are in good shape to install VoIP phones, which run off Ethernet, of course. Some systems can share an Ethernet port between your PC and phone, but it is better to run your phones from a separate Ethernet network that you can manage and provision for voice applications. And while you are at it, make sure you can provide power over Ethernet to these ports so you don't need to plug your IP phone into your AC wall outlet too. In some cases, it might be better to leverage an office move or when an older phone system is coming off lease to do these upgrades.
Do you need to upgrade your network infrastructure and switches to support the additional traffic and quality of service that VoIP will demand? Even if your wiring will support a separate voice network, you still aren't done yet. You should have a good idea about your existing data network traffic patterns, and whether you will need any virtual LANs for voiceor some other way to segregate your voice traffic.
Your VoIP system puts particular stress on wide-area links, so it is important to understand your traffic usage, particularly during peak times of day. You'll need to understand quality of service (QoS) issues and how it is managed over your wide area network links so you can provide voice traffic priority to maintain overall call quality. And while you are looking at your WAN bandwidth, be sure to examine your network switches, too. In some cases, you might have particular bottlenecks that weren't obvious with just ordinary data traffic that could become issues with carrying the voice traffic.
Most companies are going to need a good amount of bandwidth for their internal VoIP networkperhaps 100 Mbps throughout their buildings, said Joseph Bennett, the IT manager at PTR Baler, a Philadelphia-based industrial company that has been using Alteva VoIP products for about a year now. But we did need to upgrade our switches to support power over Ethernet because we wanted to power all our phones from the wiring closets. Even with these upgrades, we are still saving around $2,000 to $3,000 a month on our phone bills, which works out to a nine-month return on the new system.
Do you have multiple branch offices or remote users that you want on your VoIP system? Part of the power of VoIP is having a "softphone" application that can reside on any PC and appear as if a user is making a call from his or her own office inside your building. This is also great for branch office employees since you can just dial an extension to reach these remote users. Some of the lower-end systems, such as Jazinga and Linksys' SPA8000, don't support remote offices. Depending on how you have configured your virtual private networks and firewalls, you might not be able to implement your first choice in VoIP systems.
Do you want your VoIP phones to integrate with Outlook, IM presence detection, and other software tools? IT managers have been seeking true unified communications for almost as long as PCs have been around, and certainly VoIP is a great first step towards this. While you don't need VoIP to unify your telephony with your computing apps, it is a lot harder to pull off without it because analog lines aren't as flexible as VoIP ones.
Microsoft, IBM/Lotus and others have been doing a lot of integration work to enable this functionality with their email and Instant Messaging platforms, but be prepared to spend some time understanding what software is required and what add-ons you'll need for both your PBX and your email system to enable these features. Ideally, you want your IM client to know when you are on a phone call, or be able to call people on your buddy list, or move voicemail messages into your email inbox, or other common tasks that blur the lines among the various communications applications.
David Strom is a freelance writer living in St. Louis and the former editor-in-chief of Network Computing magazine, DigitialLanding.com, and Tom's Hardware.com. He has written two books and numerous articles on networking, the Internet, and IT security topics. He can be reached at firstname.lastname@example.org and his blog can be found at http://strominator.com.