How to Design VoIP Networks

When deciding to transform your communications infrastructure into a VoIP based system, it's important to understand the impact this will have on your networks. It's true that VoIP combines two disparate systems - the PSTN and the Internet - by removing one of them. The consequences will be that you have to change the way you manage your Internet connection due to the unique requirements of VoIP.

It's important to know that you need this management irrespective of the technique you use to implement VoIP. Whether you build your own system or use a Hosted PBX VoIP system, you still need to make changes to your network to ensure the two system get along smoothly. The reason is that even though VoIP is an Internet application, it behaves very differently from most others. When you load a web page for example, you can wait at your leisure while the page loads each element in the order in which they arrive. Even when you're watching a Youtube video, you're willing to wait for several seconds which it loads. And as it's playing, it downloads more data and creates a buffer.

VoIP on the other hand is real time. The data has to reach you in order and at the same time that the other person is speaking. There's no scope for delays and nothing can be buffered because the system doesn't know what the other person is going to say! It's even more demanding than live streaming cause there can't be a delay of more than a few milliseconds - and don't forget that the same restrictions apply to your own voice data.

To solve these problems, it's important to keep your Internet lines free - at least that part of it which is used by VoIP and to give priority to VoIP data compared to less critical traffic. This means setting up your routers to prioritize VoIP. Some routers such as Cisco's do this automatically. It also means setting up a Virtual LAN or VLAN where VoIP gets its own dedicated bandwidth and is treated as another network entirely. This prevents spikes in regular Internet traffic (like downloads for example) from adversely impacting VoIP by clogging up the pipes.

Any competent network manager should be able to make these changes in your network infrastructure. But the onus is also on them to periodically audit VoIP performance and decide if any changes are needed such as increasing the amount of bandwidth allocated for it. As your company grows, so will the complexity of your VoIP and network infrastructure