Queue - January 2009

content. Sitting right below that waist is what we call a strategy layer. The world today has lots of different ways of communicating, from dumping stuff into the USB memory in your phone and walking across the world—that’s a perfectly viable way of communicating—to using all of the different wired and wireless connections we’ve got. At runtime you should be actively figuring out the best way to communicate.

Going forward, it looks like there’s going to continue to be a multiplicity of ways to communicate because there’s no one right answer for communication. You really want a networking infrastructure that deals with what it’s got and is smart about it and has that pretty much built into the stack. CP Let’s talk a little more about that narrow waist—that is, the point of unification between the range of choices above it and the range of choices below it. I want to talk a little more about the choices below it because it sounded to me that you were saying something that I’ve been hearing from an entirely different perspective from folks like Jon Turner, who were looking at building connection devices in a world in which you have a large number of available processors and a lot of processing power, and the ability to virtualize middle boxes and allow people to run completely different protocol suites.

It’s not just TCP/IP, but whatever makes sense for their particular applications and problems concurrently in the same infrastructure. It sounds to me like you’re saying at some level we’re headed that way already just in the multiplicity of technologies, and this is a technology completely consistent with that perspective. VJ I think we’re actually going in different directions. It’s going toward a good end, but to my mind Jon is trying to pull the waist down. The waist in the protocol stack is something that [Internet pioneer] Vinton Cerf talked about many years ago, and I think Vint was the first to point out that in the ISO OSI stack, which is just a cylinder with layers that more or less look the same, most of the layers have a bilateral relationship with their peers—for example, in the link layer both ends of the link have to be using the same way of framing packets and making bits.

There’s some agreement there, but it’s only between the two ends of a link. The applications at both ends of the communication have to agree on the transport layer that they’re using and the session layer and the things going above them, but it’s an agreement that’s happening between two applications on two hosts in two parts of the world—purely bilateral.

The network layer is the only one that touches everybody—it’s the only multilateral agreement. Vint said you can have lots of innovation above and below it, but it has to be the same everywhere. You want to make it as simple as you possibly can so that it can be universal and not constrain what’s above and below it. He expressed all this visually by drawing the protocol stack not as a cylinder but as an hourglass with the network layer as its narrow waist.

For those of us who bought heavily into the Internet religion, exactly what and where the waist is, is a really crucial thing; it’s the linchpin of the architecture.

I see the work that Jon is doing as pulling the waist down toward Layer 2 and saying we want to be able to virtualize and specialize it, making it much more universal than Layer 2 is today.

I want to push the waist way up and hope to generalize the context of what a network is. In Jon’s model—and I hate putting words in somebody else’s mouth—the networks have wires. 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.

In the late 1980s there was a post being forwarded around about never underestimating the bandwidth of a 747 filled with tapes, and at the time that was just an unobtainable bandwidth for our communication technology. I tried to redo the calculation recently for a 747 filled with Blu-ray disks and got 100-terabits-per-second transcontinental bandwidth, which is still better than you can do from any carrier infrastructure.

We should have a very broad definition of things that move bits, and all of them should be able to come into our networking tent. Particularly because of the decreasing cost of storage, bits today get moved a lot of ways that aren’t on wires, and it’s really unfortunate that we see the world split into these two camps—operating system and storage people deal with bits that are on memories or on disks or on tapes; and communications people deal with bits that are on wires—and we don’t talk except when we’re forced to.

These are two utterly disjoint communities with different views of the world, but the bits are the same. The bits don’t know whether they’re on a wire or a disk. And we shouldn’t care. I would like to move us to a world where that distinction is simply not relevant anymore. The bits are bits. You give a name, you get the bits. Q