Putting it all together
No matter how you decide to do it, be sure to experiment with less critical systems before you try to restrict the traffic into the important stuff. Ultimately, you want to be able to evaluate the network impact of moving all the relevant systems and actually running them in production with real users -- so don't test by yourself off-hours and call it done. Instead, consider allowing WAN emulation to stay in place for a week or even longer, ideally during periods of high usage. Unless you're unlucky enough to experience a failure of the hardware you're using to do the emulation, you can always loosen or disable any bandwidth and latency restrictions if users start to revolt.
In fact, that's the point. If users cry uncle when you flip on the WAN emulation, you can simply turn it off. That's generally not the case when you've ported workloads into the cloud. By testing the cloud conditions ahead of time, you'll avoid unpleasant surprises.
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