Shunra's network-testing crystal ball gets better
VE 4.0 adds much-needed automation, new features to WAN simulation engine
The other new shape is the Twister. This Shunra link modifier creates alternate traffic paths while the test is running, adding a user-defined level of uncertainty to the simulation. Twister can change the route a packet takes based on a variety of criteria, such as probability, time, and packet count, so test simulations depicting backup WAN or load-balanced links can be executed in the Shunra VE. When the predefined criteria are met, Twister shifts traffic to the secondary link, dynamically changing the data path.
After the WAN is detailed in Visio, it is pushed out to the appliance and the emulation starts. While a simulation is running, testers may view real-time statistics of traffic as it passes through the WAN cloud shape. In previous releases, only limited information was available, but in 4.0, scrolling charts in VE Reporter display exactly what is happening in the WAN emulation.
Automatic for the people
Several new modules in 4.0 help automate the testing process. Benefiting from tight integration with Mercury LoadRunner and Segue SilkPerformer, the new VE Predictor manages the number of load generators, the number of virtual clients, and the WAN topology (previously described by VE Modeler).
Using a script created in LoadRunner, I devised a test plan in VE Predictor to control the LoadRunner injectors and define service level targets. I really liked that I was able to create and execute the test from within VE Predictor, taking advantage of LoadRunner’s scripting and load-generation engine, and then view the test results in an easy to read graphical layout.
Another new module, VE Profiler, takes this automation a step further by allowing testers to define a range of link speeds and WAN conditions, instead of a single WAN definition as in VE Predictor. What makes it unique is that testers can define a matrix of test criteria to evaluate. For all of the parameters (such as bandwidth utilization, latency, packet loss, and virtual users), testers can set the starting value, a maximum value (Shunra VE supports up to OC12), and define the step increments. VE Profiler also uses a LoadRunner or SilkPerformer load generator and test script during its execution.
At the end of the test definition wizard, VE Profiler calculates the number of iterations required to test all combinations of parameters and will estimate the time to completion. One thing I quickly found out is that I had to stay a little conservative on the ranges I wanted to test, and also the number of parameters, to get a test done in a timely manner. At first, I created a test that was going to run over 15,000 iterations and would have taken about two months of continuous running to complete. Use larger step values and restrain parameters to just what you are interested in for best results.
One of 4.0’s impressive new features is VE Reporter, a very comprehensive reporting and graphing utility that provides in-depth information for each test scenario. Previously, users had to take on faith that the Shunra appliance was working correctly. Not any more: With each test iteration, VE Reporter stores a wealth of data including number of packets in the cloud, minimum and maximum latency, bandwidth utilization on each gateway, and network quality.
All of this data is available in easy-to-view graphs and can be exported to Word, Excel, or HTML. VE Reporter offers excellent visibility into performance bottlenecks by displaying critical traffic information at each point of the simulation.
The Shunra VE 4.0 suite is an indispensable tool for large organizations that need to “field test” new applications but want to avoid costly field trials. The new modules are welcome additions, and the two new shapes really help round out the package. I am excited to see the integration with LoadRunner and SilkPerformer tied in with VE Predictor and VE Profiler, and the level of detail found in the reports is tremendous.
The one downside is Shunra VE 4.0’s cost: the $70,000 price puts this out of range for all but the largest enterprises. If you have the budget, though, the cost is worth it if IT can look into its Shunra crystal ball and know ahead of time just how an application will behave.