Testing is a big deal. Very often though, we spend days writing unit tests only to forget that our code must play well with others. In the real world, how responsive will a new AJAX interface or RMI Swing application be?
In our load testing environment, we've introduced a network nightmare bridge. This handy little box sits between us and our server (or between any two networked devices). We enter maximum bandwidth, milliseconds of round trip delay, and percentage of packet loss and instantly we feel the effects. Most versions include monitoring and statistic interfaces.
We can simulate long links across multiple countries, poor people on dialup, a lossy VPN connection, WiFi, etc. Really, anything we can think of.
Thinking of opening a new data centre and wondering what the latency effects will be? Got a customer who's using your WAN replicating software over a lossy VPN link and wonder how it performs? This little box is excellent for all these sorts of things and more.
The best part is It Just Works™.