What Should the Department of Defense's Role in Cyber Be?

Any emerging threat presents new challenges on policy, legal authority, budgeting, such as we have witnessed, for example, since 9/11. And today, in the field of cyber, we want to start by asking really a fairly basic but I think important question, and that is, what is the role of the Department of Defense in defending the country in cyberspace? What should we expect, if a bunch of malicious packets, or potentially malicious packets, come barreling at us--or come barreling at the same facilities in cyberspace? I am not sure we have a good answer to that. And if we figure out what we expect, then the question is, can the government do what we expect? Does it have the ability and the authorization to do it?