Use WebAvalanche to see how much your net can take

Use WebAvalanche to see how much your net can take

The Caw Networks device can put your infrastructure to the test. Report shows response time (lower, blue curve) gradually slowing as rising number of TPC/IP connections to a server (middle, red curve) strains a Cisco switch.

With other components, it can simulate 20,000 transactions per second in a controlled data landslide

An avalanche, in a network test environment, sometimes finds problems before they cascade all the way downhill.

[IMGCAP(1)]The WebAvalanche test device from Caw Networks of Santa Clara, Calif., costs about $20,000 for a baseline unit. Price notwithstanding, it could benefit any agency that posts public information on the Web or strives to maintain a robust IP infrastructure.

To adequately test the performance of large-scale environments, WebAvalanche requires a second component called WebReflector. WebAvalanche simulates user volume, whereas WebReflector simulates data clusters and servers.

The GCN Lab has adopted the Caw Networks test suite for reviewing servers, communications hardware and Web appliances.

Servers historically have been evaluated in a test bed that consists of client PCs with special software to simulate network traffic.

Bigger test bed

But as servers have grown in speed and capacity, the size of the test bed also has grown. The GCN Lab stopped testing servers when the required test bed population grew beyond 32 fast PCs, about three years ago.

In the interim, the lab used another vendor's test equipment for communications hardware. It differed significantly from the Caw Networks devices, which can program the tiniest details'even specifying which files the imaginary users want, and where the files are located in server directories.

It's as if you could order up a landslide of only red rocks, or only rocks weighing less than a pound.

With WebAvalanche's programmable tests, the lab can dig deep into server strengths and weaknesses. We can simulate 20,000 transactions per second, with each user having different characteristics'-say, some users go to one page and stay there, while others click around and still others blaze through as if spidering the whole site.

[IMGCAP(2)]WebAvalanche supports up to a million concurrent connections, each seemingly from a different IP address. Using cipher suites, we can simulate different browsers for all those users as well as delayed or lost packets that force retransmission requests.

We can test all aspects of a particular piece of equipment or its individual components. For example, we have found some servers are fine as straight data servers but terrible at streaming media applications.

That sort of detailed performance data means dollar savings in a network infrastructure plan.
The Caw test suite can predict whether or when a device will fail under load. If an ordinary server has 20,000 users trying to get data packets, for example, it's going to start to crash. Other devices such as high-end switches will remain stable under almost all circumstances.

Apples to apples

The test suite's results permit comparing one system with another so long as the tests are identical. Each test should start at a base level and step up by increments until failure occurs or the test parameters are complete.

Although the results are fairly complex to analyze, data sheets can be overlaid to show the better system for a particular purpose.

It's very easy, however, to program a test incorrectly or to run a test whose results differ from what you thought you were getting. Trial and error are necessary to learn exactly how to evaluate a particular network device.

The $20,000 price for WebAvalanche means that only serious testers can justify the purchase. If you're serious, you could hardly ask for a better helper.

About the Author

John Breeden II is a freelance technology writer for GCN.

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