(Please see next post for update)I have been trying to measure WAN efffect over an application I am working on. Due to a bug the application was running in SSL and I was quite surprised by the results.
After investigating it a little I want to share with you the following information. https (SSL) requests to the server involve two extra round trips for certificate authentication and key exchange. As a result a short HTTP request will require 3 times the network round trip time (6 times the latency). For example if latency is 90 ms and server time is 20ms https request will be 90*6+20= 560ms. While an http request will require 200ms. Quite impressive difference.
Saying that it is extremely important to reduce number of https requests to a server combining https requests is 3 times more important than regular http requests.