Tse Mac, Niosii

This is because your system is receiving more packets than it can handle. If you need your system to accept all the traffic you are sending it, you'll need to speed it up. Have a look at this article (http://www.altera.com/support/examples/nios2/exm-ethernet-acceleration.html?gsa_pos=6&wt.oss_r=1&wt.oss=nichestack%20speed).