In Return to Castle Wolfenstein, you change your maxpackets limit by going into your config file. It should be in your program files, where the game is located. Try to set the max fps to the max. In the osp mod you can change it by typing /forcefps <then the number desired>.
you can check on the maxfps by typing "/com_maxfps" in the console. Also try to set your maxpackets to the limit. These can dramatically improve your gaming performance and give you an edge. Although a lower maxpackets might give you a lower ping, a higher maxpackets gives you a more smooth performance.