Citrix NetScaler test summary

Summary of test of Citrix Systems’ NetScaler Application Delivery System.

In a single box, the NetScaler Application Delivery System sums up much of what’s right, and some of what’s wrong, about the Web front-end market. The device bristles with virtually every acceleration feature available (see features sidebar), including caching (which we didn’t test), support for complex application-layer switching, SSLCi offload and HTTP compression. And it’s a strong performer in some tests, scaling to the highest levels possible when it comes to connection count, TCP multiplexing, and goodput (see scalability test results).

For all that, though, the appliance reached limits in some of our performance tests. In some cases, enabling HTTP compression actually increased response time, even with very low transaction rates and user access speeds (see services test results). Citrix says compression results are better with Version 6.1 of its software (the company supplied us with Version 6.0), but we did not verify this. Also, the device does very well in TCP multiplexing tests only when users have longer ‘think times’ between page requests. With rapid requests from users, there’s relatively little offloading of TCP processing from servers. For its part, Citrix attributed its subpar results to our test configuration, especially regarding our lack of caching on Web front-end devices and in client browsers. Fair enough, but other devices did better running these same tests, suggesting that perhaps there are limits to this otherwise capable performer.