In his latest ComputerWorld article, David Strom takes a look at how to harden your network and Internet infrastructure to get the best results out of a digital voice deployment and asks 7 questions. I’ve put my answers in italic.

1. What is your present Internet connection and how much bandwidth will you need for voice?

In a worst case scenario a VoIP call uses about 80kbit/second/channel - that is 80kbps up and 80kbps down. On the LAN this shouldn’t be a problem but while most broadband connections can handle this in downstream, upstream is the bottleneck here. If you’re going to use your broadband connection exclusively for all your voice traffic, get a dedicated SDSL line at least.

2. What kind of wiring is in your walls?

This is pretty simple: get CAT5 UTP cabling at least, nothing less will do. The article states you might want to consider separate cabling for voice but this removes one of the major advantages of a VoIP deployment: one set of cabling for both voice and data. If you really want to separate voice and data traffic, install VLANs.

3. Will you need to support remote users that are working outside your headquarters office?

Apparently some PBX systems, such as Linksys’s entry-level SPA9000, require all your users to be inside your LAN. Stay clear of these kind of systems, because you’re removing one of the bigger benefits of an IP PBX. If you want added security, put your IP PBX in a VPN; if you want convergence, try the Nokia E-series.

4. What will you do with your existing analog phones?

My advice: dump them! You don’t want these things around in your shiny new VoIP deployment and you’ll miss a great deal of functionality. IP phones are not necessarily more expensive than analog phones. If you really need analog devices in your network, for example when your IP PBX doesn’t include an integrated fax server, use an ATA (Analog Telephone Adapter) to connect your devices or better yet, get a decent IP PBX ;-)

5. Can you keep your existing inbound phone numbers?

People often forget to ask this question and confuse a VoIP PBX with Internet Telephony. Most VoIP providers will not be able to port your existing phone numbers to their network. Some do, but think twice before handing over your phone numbers to an Internet based provider. Alternately, install an analog or ISDN card in your IP PBX and keep your landlines for inbound traffic.

6. Do you need to upgrade your network switches and routers?

If you’re still working on 10Mbps hubs the answer is: Yes, you need at least 100Mbps switches! If you want to separate voice and data traffic, you want to make sure that the switches support VLANs. If you’re going to do a lot of voice traffic over the internet and you negotiated a good SDSL contract, you might want to consider QOS for your routers as well. My personal recommendation, if you still need to buy new switches, is: get Power Over Ethernet (POE) support. This allows your IP phones (if they support it) to draw power from your network and free up a power socket at every desk.

7. Do you really need to own your own IP PBX?

No, you don’t. But think twice before completely outsourcing your PBX to a hosted provider. You absolutely want a guaranteed internet connection, and perhaps even a backup one. You’ll also want to make sure if the provider can port your existing numbers to their service. Don’t forget, if your internet connection goes down you have nothing. Not even local extension to extension calling within the office.

So, these were my answers. If you want to know more, read the original ComputerWorld article.

This entry was posted on Friday, June 1st, 2007 at 10:16 CEST and is filed under Network. You can follow any responses to this entry through the RSS 2.0 feed. Both comments and pings are currently closed.