I am designing a network for a fictional company as part of a school project. I'm looking to implement VoIP into the initial network structure - I have heard this can be implemented along side the regular network traffic and the two can exist side by side. Is this true?

I would also like to know if you could provide some assistance in finding servers to research/build that supply my three offices - in three separate geographical areas - with VoIP connectivity.

Can the data be sent out completely digitally across the lines through a VPN (I plan to use a Citrix VPN server for all traffic) from PBX to PBX?

Any advice as to where I can look up product documentation on purchasing PBXes (as I plan to have it all "in house") is also appreciated.
- Andrew J. Petrola

You can run regular network traffic and VoIP on the same cable if you have the right network equipment. This involves something called quality of service (QoS). To support QoS, you will need to have switches that have the brains to be able to distinguish the different types of traffic and give priority to VoIP in order to eliminate jitter or other problems from interfering with the quality of the IP call.

There are several resources you can look at for information on ways to design your network. The first three vendors I can think of are Avaya, Cisco and Nortel. There are others, but these are the three that I am most familiar with. You can send the VoIP traffic over a VPN, but there are issues you need to examine. Depending on the particular vendor, you may be encouraged to look at a VPN appliance, a piece of hardware dedicated to VPN functionality and not a software-VPN-type system that runs on top of a Windows and/or Linux server.

When running VPNs and VoIP, you need to consider the latency of the connections you will have at each location and how long the packets take round trip to and from each location. The lower the latency, the better your communications will be. One potential way to help keep the numbers low is the use the same Internet provider at each location. Theoretically, you should be able to keep all your VoIP traffic on the carrier's network without having to hop around various peering points to get the traffic to where it is going. Depending on where your hypothetical locations are, it may be possible for a carrier to home all your Internet connections out of the same or nearby points of presence for the carrier to further reduce the latency you might see if using different carriers or points of presence that are widely separated geographically.