5G needs virtualisation. In relation to the mobile packet core, specifically, there are four main reasons for this:
- Scalability: to enable the capacity of the mobile core to be scaled up flexibly and dynamically to support rapidly growing data volumes
- Cost: the replacement of dedicated hardware appliances supporting network functions by Virtual Machines (VMs) – and other modes of Virtualised Network Function (VNF), such as micro-services and containers – running over COTS hardware in theory enables telcos to scale capacity much more cost-efficiently
- Latency: virtualisation, along with separation of the control and user plane within the core, allows dynamically scalable data plane capacity to be brought physically closer to the end user and application
- Network slicing: to enable dynamic, automated network-slicing capabilities, which depend on being able to spin up end-to-end virtual networks on demand, based on the variable networking requirements of individual clients and use cases.
However, the effort to define and standardise the 5G core and its virtualised elements – driven by the 3GPP standards body – has not been carried out in sync with the broader industry NFV project, nor does it fully share the goals of that project – as illustrated in the graph above. (‘Northbound’ means functions that rely on the transmission of operational data from core functions to the higher levels of the stack and back again, e.g. management, service creation / assurance, orchestration, apps, IP layer, etc. ‘Southbound’ is the core functions that face the other way and are involved in effecting the delivery of those services across the physical network layers.)
By contrast, telcos’ investment in NFV and SDN – both internally and via their engagement in various open-source programmes – has hitherto focused in very broad terms on the management and distribution of data flows, both as a cost centre (acquiring, deploying and operating the equipment and software involved), and as an enabler of service innovation through flexible and dynamic connectivity adapted to specific applications and use cases.