* WAN emulation help to develop WAN-friendly apps
In the last couple of newsletters we discussed our continued amazement that for as long as either of us can remember, IT organizations develop applications over a LAN and then deploy them over the WAN. When these applications run poorly over the WAN everyone scrambles around to implement an expensive workaround. In those newsletters we asked the rhetorical question: “How about writing applications that run well over the WAN?” Over the next three newsletters we’ll discuss WAN emulation as a tool to help IT organizations develop WAN-friendly applications.
Before we begin the discussion of WAN emulation it is important to realize one important fact: a relatively small increase in network delay can result a very significant increase in application delay. We discussed this phenomenon with two IT professionals, a manager of technology, architecture and engineering for a large, international law firm (The Technology Manager) and the other a lead performance engineer for a Fortune 500 financial institution (The Performance Engineer). The Technology Manager stated that application performance does not increase linearly as network delay increases. He added that in many cases network delay of 20 msec or less has minimal impact on application performance, but as network delay increases past 20 msec that the application delay “shoots up.” The Performance Engineer stated: “An application that will work fine with 1 msec of latency will sometimes run like a dog when there is 80 msec of latency.”
One class of tool that can be used to test application performance throughout the application lifecyle is WAN emulation. These tools are typically used during application development and quality assurance and serve to mimic the performance characteristics of the WAN; e.g., delay, jitter, packet loss. One of the primary benefits of these tools is that application developers and QA engineers can use them to quantify the impact of the WAN on the performance of the application under development. For example, these tools can quantify the impact that an increase in network delay would have on application performance, Ideally this testing takes place while there is still time to modify the application.
Next time, we’ll discuss in detail the value of WAN emulation tools. In the mean time, if you want to read more about WAN emulation, you can download the 2008 Application Delivery Handbook, available at not cost from Webtorials.
