Network Latency

It's not uncommon to get complaints from your end-users about response times, and immediately blame network latency for the problems. Here's a good article that talks about the different sources of latency that an end-user may experience.

It's interesting to note the author lists proxy servers in its own category as one of the areas to check for latency.

As latency has become more of an issue, it's a topic that WAN Optimization vendors have spent a great deal of time explaining and targeting. Almost all the vendors have a good story about how they address latency in reducing the application wait times for end-users.