When you join a multiplayer Wi-Fi server, the terrain does not load properly 9/10 of the time. It lags the host and it happens when you travel a little way from where you joined. This is annoying because you have to "relog" to load the terrain. This also happens in the nether. I think it is the host, because I traveled far from where I joined, reloging to do so, and when I went to make my way back to my house, where the host was, terrain was loading. Not necessarily smoothy like it should, but it was loading. That was until I got close to where the host was again.