broadcast its interest in that file, and the nearest machine with an authentic copy would respond. File names in a CCN world look superficially similar to URLs (for example, /parc.com/van/can/417.vcf/v3/s0/Ox3fdc96a4…) but the data in a name is used to establish the file’s authenticity and provenance, not to indicate location.
It’s easy to see how much sense this makes compared to the current client-server model. Say I’m using my Apple TV box to browse my Flickr photo collection on my big-screen TV. To get each photo, the Apple TV has to connect to Flickr, which is hosted on some remote data center owned by Yahoo—it could be in Utah or North Carolina, for all I know. The request has to travel from the Apple TV over my Wi-Fi network, into Comcast’s servers, then across the Internet core, and finally to Yahoo. Then the photos, which amount to several megabytes each, have to travel all the way back through the network to my TV.
But the photos on Flickr are just copies of the originals, which are stored on my camera and on my laptop, about 15 feet away from my TV. It would be much smarter and more economical if the Apple TV could simply ask for each photo by name—that is, if it could broadcast its interest in the photo to the network. My laptop could respond, and I could keep browsing without the requests or the data ever leaving my apartment. (In Jacobson’s scheme, file names can include encrypted sections that bar users without the proper keys from retrieving them, meaning that security and rights management are built into the address system from the start.)
“The simplest explanation is that you replace the concept of the IP address as the defining entity in the network with the name of the content,” says Lunt. “Now all the talk in the network is about ‘Have you seen this content?’ and ‘Who needs this content?’ as opposed to ‘What is the routing path to particular terminus in the network?’ It’s a simple idea, but it makes a lot of things possible.”
For example, now that memory is so much cheaper than when the Internet was first built, it’s becoming more economical to cache popular content at many places throughout the network. This minimizes the distance content has to travel to reach end users, and hence the amount of bandwidth consumed. Lunt uses a real-world analogy. “It used to be that if you had a store and you needed a product, you called up the factory for delivery and they sent a truck,” she explains. “That model works for a small business in one town, but it doesn’t scale up to a nationwide or global network. So people have built warehouses where you can cache a lot of stuff, and then people order from the nearest warehouse. You can have a very efficient system without having to go back to the factory for each order.”
Similarly, in a content-centric network, if you want to watch a video, you don’t have to go all the way back to the source, Lunt says. “I only have to go as far as the nearest router that has cached the content, which might be somebody in the neighborhood or somebody near me on an airplane or maybe my husband’s iPad.”
Of course, caching data at different points in the network is exactly what content distribution networks (CDNs) like Akamai do for their high-end corporate clients, so that Internet videos will start playing faster, for example. But in a content-centric world, Lunt says, the whole Internet would be a CDN. “Caching becomes part of the model as opposed to something you have to glue onto the side.”
Tinkering with Applications
Computer scientists have been discussing the idea of name-based (as opposed to location-based) networking since the 1970s. But the proposal began to pick up steam in 2006. That’s when Jacobson, who’d done stints as head of the Network Research group at Lawrence Berkeley National Laboratory and as chief scientist at Cisco Systems and Packet Design, joined PARC to lead a new Content Centric Networking research program.
PARC had been operating as a contract R&D lab—independent of Xerox, but wholly owned by it—-since 2002. Its business model is to build internal intellectual property and expertise, often with the help of government funding and university collaborators, and then to get the technologies to market through
