Colt Technology Services Group says it plans to start a three-stage company-wide deployment of NFV capabilities in 2019. What will that entail? The ability to use generic universal CPE (uCPE) supporting virtual firewalls, cloud-based WAN acceleration and SD-WAN.
To complicate matters, the use of generic CPE might clearly be an instance of NFV, but virtual firewalls, WAN acceleration and SD-WAN might properly be considered SDN applications.
That illustrates neatly the problem we have when describing network virtualization.
As a practical matter, it sometimes can be difficult to understand precisely what a “virtual communications network” actually does. It also can be difficult to understand how a "virtual" network is created, as that most often includes a mix of changes broadly including both network functions virtualization and software defined network adaptations.
Network functions virtualization (NFV) is one key aspect of virtualization, but not the only key aspect. It also is hard to understand what a “network function” is, in terms of “virtualizing” it.
Software defined networking is the other key building block, and arguably is even more important where it comes to new service creation, where NFV mostly is about lower capital investment and operating cost.
So what are examples of network functions that can be virtualized? Routers, mobility management,policy and charging rules, session border controllers,session initiation protocol and media gateways. Providing IP Multimedia Subsystems functions (IMS) provides another example.
That is the terrain of NFV: separating data and control planes and allowing compute and control functions to be moved back from remote network elements to more-centralized locations.
SDN is more centrally related to enabling remote control of services. Software-defined wide area networks (SD-WANs) provide one good example. But supplying firewall, antivirus, video or parental control services are examples of SDN virtualization.
Note that, in general, NFV deals with network optimization, while SDN tends to involve customer-facing features.