expensive bandwidth for this really cheap—and getting cheaper—disk storage by pulling this stuff off the disk.

So, the first part is there are lots of opportunities for carriers to have storage somehow be part of the communication model, and if you go to this “exchange-named content” view of the world, bits in a wire, bits on a disk, and bits in a memory are indistinguishable; they’re all just storage. You get them all the same way: you give a name, you get back bits, and carriers can leverage that.

The second part is, because in the current conversational model the network is blind to the bits, we take this richly connected fabric of the world with multiple links going everywhere and put a spanning tree on it, so

“For content networking, a guy on a bicycle with a phone in his pocket is a networking element. He’s

doing a great job of moving bits.”

—Van Jacobson

between any source and destination, there’s exactly one path. We have to do that because we have to prevent loops, and we can’t prevent loops at the content level because we don’t see the content. But this is a global ordering on the network. It says no matter how rich your connectivity is, there’s only one way to get to a particular source, and if some party in that one way decides to play games with you—if they decide not to carry your bits—then you’re hosed. It’s now a black hole: you can’t get there; they can’t get to you.

If you go to a content model, you completely stop caring about loops because when a piece of content shows up, you say, “Do I already have that? OK, duplicate, toss it.” That means you can take this nice, rich network graph and use the whole thing, from anywhere. CP The caching gives you a suppression mechanism that lets you actually deal with the fact that, if there’s a loop, it’s going to go away. VJ Right. CP Because you’re using the LRU instead of the MRU, it creates an interesting model of how you would attack it. An attack would involve a really complex hammering of a cache whose size you probably don’t know. VJ And you don’t know its replacement policy. Typi-

cally when you design these things, you put in enough randomness so that adjacent nodes keep different things. Even if you can hammer one guy, the guy upstream, or immediately downstream, has a different policy and has still got it, so it’s a local repair action. You make a robust fabric where bad actors can have very little effect because it’s possible from the end nodes to route around them.

Our first application was doing voice-over CCN. We did IP telephony but over CCN rather than IP. We basically took the linphone client, whacked out the UDP stack, and replaced it with our CCN stack. The little laptops that we first ran it on had Ethernet, 802.11, and Bluetooth interfaces. If you’re doing voice-over IP, the call is bound to a particular interface address, so it starts up and you bind it to the Ethernet. If you unplug the Ethernet, you’ve hung up the call.

In CCN, the call is bound to the user who’s making the call. It’s bound to a name, and we made our names include the user identity, so when you’re trying to make a call, you broadcast out to all your interfaces, “Does the identity of the party that I’m trying to call exist? Is there a CCN phone that handles this identity?”

You spread your traffic over all the ways that you have to communicate. In the initial implementation the callee replied to those three. You take the first reply and say, “OK, I can talk to him and, since this reply got to me first, the interface it arrived on is the fastest way to talk to him.” With all three interfaces, it would start on the Ethernet, adaptively figuring out what worked best.

If you unplugged the Ethernet, it would detect the link loss and go back to broadcasting, “OK, I want the next packet of the call,” to the remaining two interfaces, then unicast to the interface that answered first. If you turned off the access points so it couldn’t get Wi-Fi connectivity, it would move over to the Bluetooth.

If you plugged the Ethernet back in, it would go back to the Ethernet—it would just adapt to whatever it had. Bluetooth has no IP address, so it was just using the link-level broadcast for the rendezvous there because at the CCN level, you don’t care; it’s whatever works. That applies to your getting any kind of content. Your phone has got something like nine radios in it. CP Yes, it’s terrible. I give a flaming talk about the state of wireless in which I have four chipsets, all of which are operating in the same band and each of which has its own antenna—and they’re all in my phone. VJ They all have different ways of communicating, different cost profiles, and different distance profiles. In CCN the waist of our layering is these little chunks of content, so right above that waist is the thing that secures the