There is a lot of 5G that is real. There is a lot that is almost surely a pipe dream, and there’s some in between. Network slicing is one of the latter. The assumption for network slicing is that a 5G network can be divided into separate, parallel, virtual slices that act as independent networks. These can then partition services, offering things like better isolation of MVNOs in wireless. Nokia now plans to bring network slicing to wireline broadband to make the concept (and Nokia’s influence) more universal, so we need to take a look at the broad mission and see if slicing is in your future.
Probably the best way to think about network slicing is to compare it to virtual machines sharing a server. Each VM “acts” like a server and is largely partitioned from the others, but they do share underlying resources and so those resources are somehow partitioned too. That could create either a permanent division of resources, or some form of elastic by-the-rules division of capacity.
The idea behind this is that there are applications of broadband that demand sharing, and today there’s very little that can be done to directly apportion the stuff being shared. For mobile services, as I noted above, Mobile Virtual Network Operators or MVNOs sell service by riding on the cellular networks of others. We also have, in the wireline world, a number of examples of division of resources. Verizon’s FiOS, for example, separates data and TV by the wavelength (which is just the inverse of frequency) of the light used to transport them. The mobile example shows a case where sharing is somewhat disorderly; direct control over the resources used by MVNOs is complicated at best. The FiOS example shows a fixed partitioning that might in some cases waste capacity.
There are two architectural models of what Nokia calls “Software-Defined Access Networks” or SDAN (being standardized by the BBF as TR-370). In the first model, the slicing is done by having a management-plane process that controls a network abstraction layer over the broadband access service. This doesn’t differ much from the current approach to MVNO hosting, except that the techniques for creating, maintaining, and connecting with the SDANs are standardized. The second model assumes that network nodes would actually perform the resource partitioning, which in theory might then use an overlay or encapsulation approach to create virtual pipes over a real one.
It’s not hard to find applications for SDAN. We already have several, as I’ve noted. It’s also possible that things like VoIP, IPTV streaming, IoT and home control, business services delivered “as-a-service”, and so forth could also use the SDAN approach. However, the question really isn’t what could be done with slicing, but what couldn’t be done without it. That’s a harder question to answer.
The distinction here is that slicing is going to cost something, particularly in its node-implemented form. You’d have to replace or upgrade current devices to make it work. The software to do it isn’t likely to be free, there’s overhead in both capacity and operations efforts to sustain it…you get the picture. Somehow that cost downside has to be offset by an upside, an application that is so clearly better with slicing that the business case for adopting it can be made fairly easily.
Do we have that? The biggest technical shift slicing creates is the ability to support independent handling of the slices, meaning that for mobile services, for example, MVNOs would have the latitude to do more of their own authorization and service signaling and coordination. That could bring about a set of mobile services very different from those of the host mobile operator’s services. The next-biggest shift is (mostly in the node-controlled model) the ability to create very strict partitioning of resources, which could be a benefit to services that needed precise service quality standards.
For the negatives, the biggest downside to slicing is that additional cost. Not only does slice management add costs for the primary broadband operator, exercising the benefits of independent service signaling and control could be expected to add to the costs borne by the virtual “slice operators”. Next-biggest is the uncertainty of the migration. The management-sliced model and the APIs are designed to facilitate an evolution from the current devices to future node-sliced services, but there are two key transitions to be made; first to the management-sliced APIs and then to the node-sliced devices. Both have to be justified, and it’s not certain either will be. In particular, if the node-sliced approach that delivers the most decisive differences in capabilities doesn’t come about, the management-sliced approach would have been pretty much a waste of time and money.
I’m not convinced that the market currently justifies slicing, and I’m not sure that it will be easy to create the justification. The problem is the classic demand/availability linkage; nobody will depend on something or even plan to use it without some assurance of availability, yet nobody will offer something nobody wants. Thus, it seems to me that Nokia and others in the pure 5G-slicing space are depending on the operators to behave as they did when they were regulated monopolies, meaning build stuff in anticipation of demand. Even then the operators would have to give slicing credibility. I don’t think operators will rush to offer slicing because they don’t see credible revenue.
That means that slicing comes along as a result of orderly modernization that can carry through the changes it requires with little or no incremental cost. There is probably nothing out there on which this orderly modernization could ride, other than 5G. In 5G/FTTN mm-wave hybrid form, 5G will shift the TV dynamic decisively to streaming. In mobile form, it’s essential to up the capacity of cells to support a mobile population that’s growing and streaming more.
That means that we probably can’t expect any form of network slicing until we get 5G core deployed in quantity, which probably won’t happen for at least another six years. We’ll get 5G, but in the 5G-over-4G-EPC Non-Stand Alone or NSA form much sooner. Nokia might hope that this new and broader approach to slicing will be applicable (in management-sliced form, at least) to the 5G NSA stuff, and that perhaps supporting even node-slicing for wireline broadband will influence how node-slicing could be used to divide a 5G/FTTN RF path.
5G/FTTN’s relationship to slicing is the big question for me. If Nokia really wants to push slicing into the mainstream, I don’t think there’s a better way to do it than to focus on the 5G/FTTN hybrid. Since this is new deployment, it isn’t hampered by legacy equipment that would be obsolete if the node-slicing model were to be deployed. It seems to me that slicing the hybrid home/business broadband access path would quickly establish a framework to validate the business case for slicing.
An imponderable here is regulatory policy. Some countries, including the US, had regulations in place that would discourage access providers from separating services from the Internet or even creating “fast lanes”. That policy has been reversed by the FCC in the US, but the reversal is under appeal. Elsewhere, the way that dodging the Internet with parallel access services would be interpreted by regulators is a question.
This is a smart play for Nokia, despite the questions. I think it could be rendered a smarter play if Nokia were to focus on 5G/FTTH hybrid access, but there’s still time for Nokia to take some concrete steps to create that linkage. If they do, they may be on to something.
