Age of Empires 2 recently got an HD remake on Steam. The game launched with several issues including low frame rate performance and multiplayer connection issues. The devs have listened to the problems and have deployed a patch to fix nearly everything. Below are the patch notes, to download the patch go to properties, betas, select performance from the drop down menu and download. If that doesn't work, try restarting steam.
The full patch notes can be found on the page.