I'm getting timed out of my own minecraft server?

So recently I set up a server for me and my friend to work on. We both can connect fine but in about 10 minutes we time out. When we time
out I see the error code: connection lost internal exception: io.netty.haner.timeout.readtimeoutexcept… Every time we time out, it says the server is overloaded in the console. The server is a bukkit 1.7.2 beta build. The server runs a min of 3gb ram and a Max of 5gb on my 8gb ram AMD quad core processor