We often mention the fact that slow network users can impact the server’s ability to scale and consequently degrade user performance (for example here ). This is fundamentally attributed to the fact that slow network users (due to high network latency or limited bandwidth) occupy server resources for longer periods of time per transaction. This negatively impacts the user experience for all users, fast or slow and a scenario that must be part of every pre-deployment performance testing plan.
This week we had a first hand experience of such a scenario. We were testing an IIS based application that under ideal network conditions (LAN) scaled to 200 users. However, the same server when tested with 200 users under WAN conditions (high latency and low bandwidth) started to bog down at around the 80 user count.
When our consulting experts analyzed the server they found a specific resource “w3wp.exe” that was pegged and had high memory usage. Additional research uncovered that this specific resource tends to degrade in performance under low bandwidth conditions. There is a fix to this problem and more information available from Microsoft at http://support.microsoft.com/kb/916984
This is just one example to the type of problems that surface when applications and networks interact. It was great to find this problem early in the testing phase rather than have his users experience post deployment issues.
I am curious to hear from you: What type of unique problems have you uncovered when applications and networks interact? (I mean beyond the obvious slowness in application response time due to network latency and limited bandwidth)
Looking forward to getting your input
Best,
Amichai
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