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What is a Virtual Network Function?

A Virtual Network Function replaces network hardware with software that can be changed and scaled to meet burgeoning 5G demands

VNFs are network services running as software processes on off-the-shelf server hardware. They replace dedicated hardware devices. By virtualizing essential network functions that were previously the domain of dedicated hardware appliances, operators can deploy new services, enhance security and tailor network performance at scale using software alone. 

Individual VNFs are deployed in the cloud as microservices, which can work independently or together to provide essential networking functionality. Examples include:

  • Network routing, such as Domain Name Service (DNS), Natural Address Translation (NAT) and Broadband Network Gateway (BNG) services. 
  • Security, such as malware detection, intrusion detection and Virtual Private Network (VPN) services.
  • Traffic analysis, prediction and Quality of Service (QoS) measurement.
  • Network and resource load balancing. 

VNFs: part of a NFVI

VNFs are often spoken of concurrently with Network Functions Virtualization Infrastructure (NFVI). VNFs are the actual implementation of network functions as software processes. NFVI is an architecture or framework for implementing VNFs on a wide scale. NFVI is a fundamental concept of data center operation which is essential to the creation, deployment, and effective scale of new 5G services. 

NFVI enables 5G network slicing, allowing various virtual networks to run on top of a single, physical infrastructure. This enables operators to divide a physical network into virtual networks capable of supporting multiple radio access networks (RANs). It can optimize resource provisioning of the VNFs for price and energy, scale VNFs and ensure VNFs consistently operate properly.

“NFV is an architecture guiding management and orchestration activities, whereas a VNF is the technology providing virtual (that is, hardware-independent) network functions such as routing or firewalling,” said VMware.

“Virtual network functions (VNFs) are software applications that deliver network functions such as directory services, routers, firewalls, load balancers and more. They are deployed as virtual machines (VMs) and have often been the next step for telecommunications providers in their digital transformation from the physical network functions (PNFs) of legacy network appliances on proprietary hardware,” explains Red Hat.

“Data centers have long used NFV, but the concept has more recently become coupled with SD-WAN to leverage the benefits in individual and remote branches,” said VMware.


Virtual Network Functions exist as part of a continuum of Software Defined Networking (SDN), a network architecture concept which decouples the control plane from the data plane in networking altogether. An SD-WAN is a Wide Area Network (WAN) implemented using SDN principles. 

SDN provides central control to a network using application program interfaces (APIs). The platform consists of three successive layers: an infrastructure layer, a control layer and an application layer, all of which are open. An SDN controller heads operations, relaying information to systems and routers using APIs. Abstracting control from the forwarding plane enables network operators to dynamically adjust traffic flow, and thereby, bring in a lot more agility into the network.

SD-WAN enables organizations to intelligently direct traffic over multiple WAN links, essential to edge computing and low-latency 5G applications. It can provide organizations with better security, higher reliability and optimize the capacity of their networks.

VNFs and 5G

Rapid technology advances, exploding demand from enterprise and consumers and new use cases in 5G require operators to fundamental changes to their network architecture. Specialized, proprietary hardware limits operator growth and flexibility, and doesn’t provide the scale needed to address future market demands.

“Network Functions Virtualization (NFV) aims to address these problems by evolving standard IT virtualization technology to consolidate many network equipment types onto industry standard high volume servers, switches and storage. It involves implementing network functions in software that can run on a range of industry standard server hardware, and that can be moved to, or instantiated in, various locations in the network as required, without the need to install new equipment,” said ETSI.


Peter Cohen
Peter Cohen
Peter is Technology Editor for RCR Wireless News. His coverage areas include telco cloud and the convergence of 5G and cloud computing. Peter's background includes IT management and a decade as a senior editor at Macworld. He and his family live in Massachusetts.

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