Beyond hybrid clouds, IoT and 5G networks there are several NFV use cases emerging in the both the short and long term. VNFs are most widely used today as a mechanism for providing a Layer 4 through 7 networking or security service, including session border controllers, load balancers and application delivery controllers, firewalls, intrusion detection devices, policy enforcement managers, DNS platforms and WAN accelerators.
CSP and enterprise IT organizations have already embraced virtual appliances to deliver these capabilities on top of virtual machines. A VNF implementation of these functions takes that concept to the next logical conclusion by making it possible to manage those functions as pure applications within a well-defined framework that can be deployed anywhere without concern as to what virtual machine platform is installed where.
Beyond Layer 4-7 VNFs
VNFs are not limited to Layer 4 through 7 of the networking stack. Lower-level physical networking equipment such as routers are also available as VNFs. Depending on the levels of performance required, service providers and enterprise IT organizations will need to decide when they can employ a VNF versus continuing to rely on physical network infrastructure.
Many service providers are gearing up to combine all these VNFs in a way that enables them to create a virtual customer premise equipment (vCPE) solution. At its most basic level, vCPE services will be employed to create a virtual platform for delivering a core set of virtual private network services to a specific location. Those vCPE offerings come complete with application programming interfaces (APIs) for programmability, enabling automation and solution extension. SD-WAN (software-defined wide-area networks) services are often run on top of these vCPE platforms to provide comprehensive site-to-site connectivity for enterprises, with add-on capabilities including WAN optimization and security functions.
From a use case perspective, when NFV first came to light, we expected virtual Evolved Packet Core (vEPC) architectures to make more headway but instead vCPE and SD-WAN have taken over as the most popular NFV use case in the last 12 months. Nevertheless, vEPC and vIMS initiatives continue to make progress as CSPs virtualize their networks with VoLTE roll-outs and lay the foundation for IoT and 5G services. We continue to see vEPC and vIMS implementations across global roll-outs though more incrementally than we originally expected.