quick DDOS question

When you DDoS a box, are you maxing out the processors capability of handling requests, or are you maxing out the 10 mbps (or whatever, its an example, i know its really low but thats what my comp is on) of network resources?

It strains CPU RAM and bandwidth, but I would say it's the CPU and ram which would probably giveway first, just depends on the size of the botnet and the limitations of the server. But for every HTTP request the server allots a bit of RAM, hard drive space, and of course causes strain to all computing resources as a result. At some point it will no longer have the ability to handle the incoming requests, thus the server crashes.