I wrote last week about some of the reasons you might want to simulate access to the cloud before going all-in -- especially if you can't justify the cost of a direct connection to the cloud. I also spent some time digging into various ways that you can estimate the end-to-end performance of an Internet connection.
Next on the list: Here's how to actually emulate that connection on your own premises with your own applications.
A wide variety of tools enable you to emulate a WAN circuit. Which one is best for you depends upon your experience with network engineering (and, generally, Linux) along with whether you think you'll need tech support. In no particular order, here are a few of the tools I've used, but many others are out there. Don't be afraid to try them, too.
The Linux kernel
Believe it or not, the Linux kernel itself gives you all the tools you need to emulate a WAN. It can handle IP routing, bridging, variable delay introduction, and traffic shaping and policing. If you're familiar with Linux and the idea of turning your favorite Live CD distribution into a router doesn't faze you, this is probably the methodology that will give you the most control and insight -- and won't cost you a dime.
WAN-Bridge is another free Linux-based WAN emulation distribution. If your goal is to set up a bridge-based WAN emulator and you don't care about emulating jitter, reordering, or asymmetrical bandwidth, this may be the simplest and easiest tool you'll find. As with WANem, WAN-Bridge is a Knoppix-based Live CD that uses Netem and TC. Unlike WANem, it's not graphical in any way, but the textual interface is simple enough that very few will have a problem using it.
The downside to WAN-Bridge is that it doesn't expose the full feature set of Netem or TC. The distribution includes the extremely helpful Ntop tool, which gives you an idea of what kind of traffic is flowing across the WAN emulator.
Vyatta is a Linux-based software router owned by Brocade; it's a commercial product, but free versions are available. If your needs are a bit more complicated and you require the full feature set of a real hardware router but don't want to buy one, Vyatta can be pressed into service as both a router and a WAN emulator. Its network emulation feature set doesn't have the same depth of latency controls as a manual Netem (or WANem) implementation would, but Vyatta lets you easily implement fairly complicated configurations that involve more than a pair of interfaces or dynamic routing protocols.