How to trigger a network slice?

BY MIKA SKARP

Network Slicing means that from a single network mobile operators can provide different service levels based on different business models. According NGMN.org, “The Network Slice Instance may be composed by zero, one or more Sub-network Instances, which may be shared by another Network Slice Instance.” But in order to provide SLAs for any connection, each slice will require admission control and tight management protocols to define how, when and where the slice will be used. In practice this means that any assured slices delivered in mobile network will need to be orchestrated around the dimensions of time and location and can’t be best effort. This requirement is already well understood by the industry and is being demonstrated in live 4G networks today.

Lacking in the discussion thus far has been a deep dive into how slices may get triggered and how the end user will gain access to and enjoy the benefits of Network Slicing. Technically speaking, there are two options: Either the Slice gets triggered by the network or the trigger happens outside of the network. Because of the admission control and management requirement, capacity orchestration within and between slices along the axes of time and location is mandatory for slice triggering to function correctly.

Our first option – that of setting triggers inside of the network - will require the employment of Deep Packet Inspection (DPI) in some formulation. While DPI is very well known, and heavily relied upon, particularly for security, it is not at all transparent. This is why employing DPI for Network Slicing has butted up against Net Neutrality and borne its share of tensions in that regard. It’s also very expensive; Inspecting every packet in the network not only requires a huge amount of processing, but also imposes considerable lag in the network. Needless to say, adding delay to the Network is anathema to the mission of 5G, and the goal of zero-delay connections. Further, and while DPI is a common element in existing networks, it does not provide 100% coverage. For example, HTTPS presents considerable challenges and the all important VPN constant kills the whole concept. As such, DPI can’t address admission control issue at all. As result, and following this path, more network elements will have to be in place to provide critical trigger-required information and control as all of this needs to be collected and centralized. In sum, and for a host of reasons, it is not a good idea try to use DPI-based technology to trigger Network Slices.

On the flipside, to provide transparency to slice provisioning and make the system easy, it makes a lot of sense to follow Cloud principles of API-enable user- or machine-initiated requests; Let the customers decide what kind of services they want to use. This not only removes the conflict with Net Neutrality but also means that slice triggering will happen outside of the network which will only need API calls to deliver the slice, exactly the way Cloud services operate. All the information required to trigger a slice, including time, location and context (the given application) will be provided to the network from outside. It is then up to the network to decide if the user will be given access to slice. This may be based on the given network and slice loads in that location, and of course the customer’s willingness and ability to pay for the service. This process is very simple, but most critically it is fully transparent. There is no doubt about whether or not AWS is somehow blocking some customers from its Cloud.

But to make all this happen, there are two key requirements, both of which are contained within Cloudstreet’s Dynamic Network Slicing platform. 1) The system needs a customer-controlled trigger outside of network and 2) The network required an element that can accept requests from the triggers and provide admission control to the network. This architecture exists already in the FirstNet specification under auspices of “Local Control” and the element in the Network is called the Dynamic Controller based on Cloudstreet’s DPC™. The best part of all is that it works already in the 4G networks. Let’s get slicing!