Evaluating IP telephony products

Tips for comparing IP Telephony hardware and software products.

If you've decided to implement an IP Telephony network, but you haven't decided on a vendor yet, you're probably

planning to evaluate a lot of IP Telephony hardware and software in the near future. You've got a lot of questions to answer. These include concerns about the hardware and software compatibility with your existing network, and of course, you want to listen to actual phone calls to hear how it sounds for yourself. You also want to verify interoperability between a number of vendors and product lines.

All of this may be easier said than done. You get some demo equipment from your salesmen, but if you don't already have a network set up, what good is it? If you're trying to set up all the equipment at once and you have issues, it's hard to know which product is misconfigured or at fault. These and other issues can make evals almost pointless.

Here are a few tips for conducting a productive evaluation:

  1. Research your tools first. Find a good product that lets you capture traffic and decodes the signaling protocol and the voice CODECS. You will need this to baseline and evaluate the different IP Telephony products objectively. Common examples include AppDancer, Viola's NetAlly VOIP, and special VOIP software for the old faithful protocol analyzers like Wandel & Goltermann, Radcom and Sniffer.
  2. Know your own network. Make sure you test during peak traffic hours. Try to test over all the components that will be involved in the final deployment. For instance, if you have any firewalls, VPNs, proxy or authentication servers that will interact in any way with the telephony equipment, be sure to test them. If you have different brands of PBXs in different locations, be sure to test those too.
  3. Plan ahead of time and be prepared. You may not get long to play with the demo equipment, and quality time with pre-sales engineers is very scarce these days.
  4. If you don't have SIP servers setup, test your demo equipment using public SIP servers. You can find a short list of them at www.cs.columbia.edu/sip/servers.html. Even if you have already made a decision on the SIP servers, testing them on public ones will give you a good feel for interoperability.
  5. Pay attention to the version of software or firmware running on the demo equipment. It will likely be different than what you receive after you've purchased. Ask for copies of the last stable release and the latest beta or pre-release code. As part of your test, perform the upgrade yourself. IP Telephony code may change quickly, and you want to get a feel for how smooth the process is, and how much time it will take to maintain the devices in production.
  6. Finally, document everything thoroughly and provide constructive feedback to the vendor.

Thomas Alexander Lancaster IV is a consultant and author with over ten years experience in the networking industry, focused on Internet infrastructure.


This was first published in November 2002

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