Verizon’s Three-Tier Model and the Adoption of SDN/NFV

In a recent interview Verizon’s CEO talked about a three-tier strategy for the company.  You start with the best connectivity, add platforms that can drive traffic, and then add content, applications, and solutions selectively where you need an ecosystem.  While the interview was focused on mobile plans, you can see it has potentially broader value in assessing changes to networks and services.

Connectivity is access to customers and sites, which to me means that you have to focus on access infrastructure in both mobile and wireline terms.  Operators sell connectivity as their primary product.  Platforms that drive traffic are things that validate connectivity, including things like the Internet and VPNs.  Most of what we call “services” are really platforms that validate connectivity.  The top layer, where the ecosystems live, would include content and also something like IoT.

One thing this characterization of Verizon’s strategy shows is that it’s a top-down approach.  You’re not hearing about SDN or NFV or even the cloud here.  CEOs start with what they want at the business level and work downward from that, a kind of technology-planning-by-objectives approach.  This is why I think so many of our technology revolutions are in trouble; they’ve started at the bottom and are groping their way upward toward hoped-for benefits.  Certainly it shows that projects a la today and senior management buy-in are going to have to converge at some point because they’ve started off in different places.

We could apply a top-down approach to “connectivity dissection” to illustrate my point.  The priority in spending on connectivity has to be establishing the access path because absent access we have nothing.  Exploiting access should really be about service platforms, and so things like SDN and NFV would be viewed by how they enhance connectivity (by cheapening it or by augmenting the platforms we can support).  But what would these new technologies do to enhance things?  One answer, provided by Brocade, is the “every customer has their own network” model.  It’s useful to look at what this could mean then dissect it into SDN/NFV terms.

Right now, we build network services to users increasingly from shared connectivity.  We build IP networks and partition them at the IP level, so they’re not really a customer’s own network at all.  The devices that create the services are shared, in VPN form for example.  If we really wanted to give every customer their own network, we’d partition below the connectivity services, which means we’d be building the “connectivity tier” or access network without protocol specificity.  It would look like agile virtual wires.  Those wires could then be connected to virtual switches/routers to create services, and the result would be that every customer would have, in effect at least, their own network.

This raises an interesting question in reference to the broad carrier model.  Should access networks, which have been incorporating more and more IP-specific features, be instead moving toward being virtual-wire or physical-layer?  This could be created using a combination of SDN and NFV, with the former providing virtual tunnels that became our physical layer connectivity service, and the latter providing the Level 2/3 overlay connectivity map.

I wonder if operators might have been better off thinking of SDN and NFV in these terms rather than in terms of things like virtual CPE or virtual EPC.  It’s not that either of these are bad applications, but that perhaps they’d make more sense in the long run if they were put into a connectivity mission.  vCPE, for example, is a nice place to host router/switching functionality if you don’t have a traffic topology complicated enough to justify a set of internal nodes (virtual, of course).

Full connectivity is usually generated by these internal nodes, where traffic routing assures there’s a path to every destination from every source.  The alternative, which is meshing the sites with physical paths, is clearly too costly.  But what about meshing with virtual paths?  If I can multiplex traffic at the virtual-path level and insure efficient traffic-handling, could I not create full-mesh networks based on edge switching/routing alone?  This is just one example of how new concepts demand we rethink the old restrictions and paradigms.

We don’t hear much about this sort of thing, no doubt in part because it doesn’t exactly fit in with the current network incumbents’ revenue/product plans.  Software-defined networking, which could use explicit forwarding control to create truly isolated virtual paths/wires, might have been an unfortunate term if we wanted to promote all the aspects of the new technology.  If “software definition” is the goal, you could accomplish it by providing various mechanisms for path control over legacy protocols using legacy devices.

If we can use SDN and NFV in the connectivity and service layers, what about that top layer, where applications and functions and content live?  It’s already clear that networks that deliver experiences will use the lower layers as services, and in fact one of the biggest promoters of “SDN” is cloud data center technology where virtual switching is more agile in tenant control than physical devices would be.  The big question IMHO is whether concepts of SDN and NFV work their way more intimately into the cloud, creating a much broader mission for themselves and linking themselves more with new revenue.

Content delivery is really a great cloud application if you have cloud infrastructure placed in enough suitable caching locations.  If you combine cloud technology with NFV for deploying instances of cache or distribution points and SDN for creating ad hoc connections, you can not only devise a more efficient CDN, you can blend it with mobile infrastructure.  And remember that mobile networks were what Verizon’s CEO was really focusing on.

IMS means “IP Multimedia Subsystem”.  The concept has been around for almost two decades, and IMS and related technologies (like Evolved Packet Core or EPC) have been the target of a lot of virtualization projects, including many in the NFV space.  But what are we really doing with these?  The answer is that we’re replicating the function and structure of legacy mobile networks but using hosted rather than fixed-box components.  Is that something like building SDN by overlaying it on legacy devices?  I think so.

The biggest challenge that Verizon faces with its three-tier plan—the biggest challenge mobile operators face overall—is how to define mobile services and infrastructure without accepting all the limitations of the physical devices, limited-capacity paths, and rigid OSI layering that we inherited.  The IP Multimedia Subsystem shouldn’t be explicitly IP at all.  If it is, then we’re eliminating most of the benefits that it could deliver to us…and to the operators themselves.