VoIP for the math impaired
Tom Lancaster
If you're like me, you often lack the time or patience to figure out the math behind some problem. And worse, when I do take the time, I'm prone to making mistakes, particularly with those pesky decimal places. That's why I like calculators.
Believe it or not, there are some pretty spiffy VOIP calculators available now. These can really be useful if you're planning a big deployment for lots of locations, or if you have a fairly active network with trunks going in a thousand directions.
Need to calculate bandwidth for a known busy-hour? Or vice-versa? Try this out:
http://www.voip-calculator.com/calculator/eipb/
What about lines to bandwidth? No problem.
http://www.voip-calculator.com/calculator/lipb/
Lines to minutes with Erlang B?
http://www.voip-calculator.com/calculator/mivp/
There's plenty more Erlang calculating mojo at http://www.erlang.com/calculator/
Or you can use a very cool web-based, online calculator at
http://www.packetizer.com/iptel/bandcalc.html
This calculator even takes into account your layer 2 header, use of silence suppression and provides MOS!
These calculators are a big help when planning, because even a small math mistake can mean the difference in poor quality and acceptable quality. Even if you really like math, you still need a sanity check every once in a while.
They're particularly useful if you want to play 'what if' scenarios with different types of media and CODECS because you can quickly change the samples per packet or other variables to find out what affect it would have on your network.
Thomas Alexander Lancaster IV is a consultant and author with over ten years experience in the networking industry, focused on Internet infrastructure.
