This article from O’Reilly goes over the impact the Slammer worm had on routers. I’ve commented below…

This article explains a bit about ReiserFS. While ext3 has likely removed the need to choose ReiserFS simply for journalling, Reiser has some performance features that make it attractive for applications that use lots of small files, such as cache engines.

High end routers make use of route caching to improve performance, usually processing the first packet the slow way so that successive packets an go the quick way. However, the worm is only one packet long, so the router’s caching is for naught. A router’s primary task is to route packets, if it gets too busy there it will drop other tasks, such as routing protocol handling. Do this on your BGP link, and you’ll flap. Flap, and you get dampened. Get dampened, and you’re offline for a bit.

This behaviour isn’t limited to the worm. You know those printer management tools that flood your network with SNMP requests looking for printers? Yea, they’ll do that too. I can’t count the number of 2am pages I had until I figured that one out.