Switching to VoIP

This is the Title of the Book, eMatter Edition

Copyright © 2007 O’Reilly & Associates, Inc. All rights reserved.

Key Issues: Troubleshooting Tools

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A great tool for adding load to a network is IPerf, which you can

download from http://dast.nlanr.net/Projects/Iperf. This package can

create streams of UDP traffic that use up the amount of bandwidth

you specify—perfect for simulating VoIP load. IPerf has a server and

client that each set up a socket for sending/receiving a large stream.

You can control the port number, protocol, and size of the stream.

In a real-world scenario, you may need to fill, or nearly fill, a call path with traffic in

order to test its behavior under heavy loads. By tweaking the amount of load you

place on the call path, you can figure out the failure thresholds for it. Use IPerf to

simulate a fixed load, and continually increase it, recording the call quality and com-

pletion rate each time you do.

Once you hit the performance ceiling, you should be able to state that a particular

link will carry no more than x G.711 calls or that a certain call path through the net-

work will carry no more than y G.729A calls. You would almost certainly have to do

this kind of simulation during off-hours.

But how can you account for the bandwidth consumption of non-VoIP applications

on the network? One way is to measure it during regular business hours, and then

add it into your IPerf simulations. ...