After you've implemented the changes needed to optimize the response time of your website, it's time to test the results in a realistic environment. Numerous WAN emulators are available on the market, ranging from open-source tools to commercial products. The WAN emulator you choose should be able to limit the amount of bandwidth your application can consume (simulating a low-speed Internet connection) as well as introduce delay. Routers are not a good replacement for WAN emulators; although they can limit the application bandwidth, they cannot introduce artificial delay.
One of the easiest free emulators is the WAN emulator from Tata Consultancy Services, available as a bootable standalone CD, and therefore requiring minimum installation and setup time.
Once you've started a WAN emulator on a dedicated workstation, you should force the traffic to pass through it by a combination of IP host routes and Network Address Translation. You can check the correct operation of the test environment easily with the ping program—the round-trip time (RTT) it reports should be approximately equal to twice the configured delay.
After you've verified that the WAN emulator introduces delay in both directions, use any of the performance measurement tools described in the "Fix Your Website's Performance Problems" article to check the performance of your website under the conditions of limited bandwidth and long delay.