Remember the concept of NGN—the “Next-Generation Network?” Some people think the Internet is it, but the Internet is a service and not really a network. Some think that it was accomplished by IP convergence, but if that’s true then what’s all the fuss about SDN and NFV about? So are we anywhere near the NGN concept, and how would we know if we were moving there? Maybe the best way to find out is to look not at what NGN is, but to start at least with what it isn’t.
It isn’t OSI. The OSI model was first articulated in 1974, and anyone who thinks that technical visionaries could anticipate 40 years of network evolution back then is delusional. We had a world where economies of scale in terms of bandwidth were prodigious because practically everything was terminal-to-host. Applications used bandwidth at such a low duty cycle that it was routine to oversubscribe trunks by 500%. A T3 trunk cost over $9000 per month in just access charges. Now we have video streaming on the demand side and flattened bandwidth/cost curves on the supply side that can make the notion of aggregation to more efficient trunking levels seem simplistic. The network of old tried to structure services in layers, and that made sense given the price/cost pictures of the time. Today, every layer is a big hit on Opex that can likely never be made up in capex.
Flattening the OSI layers has been a watchword for a decade, maybe even a generation. If you look at the SDN story objectively, you can see that a big part of the value proposition could be based on the notion that service connectivity can be overlaid on anything that provides for path meshing. Build Level 3 on top of Level 1. Or maybe build Level 4 that way. With every layer you eliminate you eliminate a level of complexity that raises management costs, and thus raises TCO.
This is why I’m a cynic with respect to SDN thinking, why NGN isn’t SDN either. We can argue that software-defined networking is networking that’s responsive to software needs, and that’s very reasonable. It’s also something very evolutionary; we can make current networks more software-controllable. We can define software-defined networking as the replacement of Level 3 architectures based on adaptive per-device behavior with one based on centrally managed behavior. That’s something more revolutionary but we’re taking new-generation network thinking and applying it to recreating what we had all along, which isn’t much of a “next generation” to me.
SDN in pure form is about contextless forwarding. You simply tell a device to do this or that with packets and screw OSI layers or other traditional models. You don’t necessarily even have to base forwarding on traditional concepts of addressing, you only need to say that for any given packet, identified by some unique set of header information, you know a forwarding rule that gets it along its path to the destination.
NGN has to be able to embrace this kind of thinking. Services are a combination of connectivity and features. SDN provides the connectivity and the cloud and NFV concepts provide the features. We should be able to build both on optics and one layer of electrical handling, and we should be able to declare that the way that connectivity and features mix is totally under the control of some great service-arbiter up in the sky…or in the cloud. Ethernet and IP are just systemic collections of forwarding rules and adaptive behavior. NGN should be able to embrace them of course—you can’t destroy the past to prepare for the future. But NGN should be able to overcome them too, to create a set of service rules that build in all the things that we have to add on in today’s networks. Otherwise it’s not NGN at all, it’s the same old generation with a face lift.
I think one of the opportunities—the greatest perhaps—that the NFV ISG has today is the opportunity to reshape NGN. Obviously NFV can define the features of the NGN in a cloud-friendly way. Less obviously, it can define the way that services relate to features. When a cloud application is built, it’s necessary to create not only component instances for the software to run, it’s necessary to create the connection framework. Does NFV simply embrace the strategies of old? Or does it redefine the notion of services and connectivity itself, to move beyond both current infrastructure models and new cloud models into something that’s both….and more?
Software defines networking if it can break the barriers of the old protocol and service models. If all we do with SDN, with NFV, is to replicate the tired old crap we’ve been using since the OSI days, why are we calling this the “next-generation network?” We are stuck in intellectual neutral here. Yes, we have to have user-network interfaces that look like IP and Ethernet, but inside the black box of the network we now have the technology and the insight to create something totally new, a black box that has external properties that are familiar and that has internal properties that are revolutionary.
This is our challenge. This is what our generation, as opposed to the generations past, have to seize. Yes, the Internet and IP were revolutionary but revolutions don’t stop with the first rush to the barricades. We have to carry on from those visionaries, even the ones who invented OSI, and not simply accept the paradigms they created when the world was a very different place than it is today. Can we do that? The answer to that question will determine whether there’s really an NGN—or just the Old-Generation Network with a new do.