Whenever I work on performance issues, the first thing that pops into my head is lost, dropped or corrupted packets. It really doesn’t matter which issue you have they all have the same impact.
Allow me to explain; when any of the previously mention issues occur, your computer will not be able to process that packet. When the packet doesn’t arrive, the receiver can’t acknowledge it. If the receiver can’t acknowledge it, then the sender waits for that segment or indicates it is missing data with mechanisms such as SACK.
In this video I show you how to get started with dropped packet analysis. The key here is to setup your screen so you can easily search and see your results without having to bounce in and out of various Wireshark panes.
As always there are many different ways to attack this issue, but I thought it would be worthwhile to give you an idea.