If forced to use tunneling of IE plugin due to firewall rules, using a reverse proxy might make the connection even slower.
This can be explained as a result of the proxy server re-using TCP-IP ports. Naturally this is sometimes only present in very complex environments, but it might be worth knowing that this can be worked around.
If the proxy server is re-using TCP-IP ports it might be needed to update the Registry with some parameters to tune the TCP-IP stack.
Normally it take 4 minutes for Time_wait connections to be freed.
After the change it will be done after 30 seconds.
This will prevent the TCP-IP stack from re-using connections.
Change the following: