A cable plant is generally about 5% of your investment, with the electronics and software being the remaining 95%. It is not worth skimping on either one. Each should have a balance of cost, capability and the ability to live through its entire lifecycle. All costs should be justified and provide a solid return on investment (ROI). You can find a VoIP ROI calculator and more information in SearchVoIP.com's Guide to VoIP ROI.
Every vendor will have a different model, but you will have the best-case scenario if you can share some information with your vendors. Obviously, not all expenditures are required, nor should they be divulged. Some will even damage your ability to bargain effectively, so be careful to share only the information that will help you the most.
When planning capacity, the standard calculation is Erlangs. There is a calculator available at www.erlang.com. When you look at the capacity, you need to know the type and kind of compression that will be used on the system. There are several factors, and all will change the capacity of your circuits. Also, look at capabilities that you want to add within a year. The reason that this is important is that in many cases it is less expensive to over-specify a circuit at the front end. Some carriers have very hefty change and cancellation fees. Some waive these for circuit increases, but some do not, and most charge for downgrades. When it comes to bandwidth, it is better to have a bit too much than not enough.
The number of simultaneous calls that you are seeing now on your PBX environment is only part of the equation. You also need to look at other means of communication, including cell phones. Some people use their cell phones for long distance because they have a nationwide plan. This may also mean that they are exceeding their limit on minutes. Adding VoIP abilities may be a nice trade between cell overages and functionality.
The best way to look at these needs is to have a power user from each department take part in a brief roundtable meeting. Systems are installed all the time that do not cover the functionality needed for each department, because departments are not part of the decision, and assumptions are made. If you are evaluating systems that have additional capabilities that may prove useful, arrange for various department representatives to sit in on a demo. This will allow for the best decisions based on all requirements of the enterprise.
With that said -- you do not want the tail to wag the dog, so to speak. Cool features that are a huge draw for one vendor may be available as a third-party application for another. Each vendor can help you determine which partners have features, but in order to do that, they need to know your current habits. A great example is the hospitality industry, in which there are good third-party applications that allow end users to check out of their rooms and arrange billing, etc., all through their phones. This may save on another back-end application that would require setup, maintenance and ongoing software support. If you can consolidate applications and functionality, the payback is huge.
In this same scenario, if you plan capacity only on voice, it may not be hardy enough for all the other functionalities without an upgrade. So here, planning is key. We want all toys in the toy box to play well together!
There are two other decisions that you will want to make right off the bat before you start evaluations. Do you want to utilize a VoIP gateway or hybrid system, or do you want a pure VoIP system? There are distinct differences between the two. In my opinion, the first is in administrative costs. In a hybrid system, you will have to maintain both environments. This can have a significant impact if you outsource the voice administration. You will now have networking folks handling the IP portion and your traditional guy handling the PBX functionality. You also have to consider how you will find out if the gateway is down. If you don't know it is down and all your calls are being routed to the POTS network, this could be another Gomer Pyle moment when you open your phone bill.
Pure environments will require some additional end-user education on the new phone functionality and feature sets. They may also require a change of some of your network electronics to add quality of service or Layer 3 switching if the network is big enough. That may not always be the case, however. Pure environments may also mean that networking has more duties for a while or may mean additional training for telco guys. But at least it is a single environment to maintain, with fewer potential points of failure.
About the author:
Carrie Higbie, global network applications market manager for The Siemon Company, has been involved in the computing and networking industries for nearly 20 years. Carrie has taught classes for Novell, Microsoft and Cisco certifications, as well as CAD/CAE, networking and programming on a collegiate level, and serves as the "Preparing your network for VoIP" site expert on SearchVoIP.com.
This was first published in June 2006