Definition

virtual network functions (VNF)

What are virtual network functions?

Virtual network functions (VNFs) are virtualized tasks formerly carried out by proprietary, dedicated hardware.

VNFs move individual network and security functions out of dedicated hardware devices into software that runs on commodity hardware. These tasks, used by both network service providers and businesses, include firewalls, domain name system (DNS), caching and network address translation (NAT). They can also run as virtual machines (VMs).

VNFs can be linked together like building blocks in a process known as service chaining. Although the concept is not new, service chaining -- and the application provisioning process -- is simplified and shortened using VNFs.

How service chaining works
Service chaining works like building blocks to link together different network and security functions.

Benefits of VNFs

Traditionally, new services and network functions are installed manually. Network engineers configure the functions along with their dedicated hardware devices or boxes. With service chaining, for example, engineers would need to manually cable together each dedicated device to link certain functions so they perform a desired sequence.

VNFs virtualize those functions, so new functions can be deployed as VMs more quickly. This virtualization eliminates the need for specific hardware.

VNFs can help increase network scalability and agility, while also enabling better use of network resources. Other benefits include reducing power consumption and increasing available physical space, as VNFs replace physical hardware. These benefits also result in reduced Opex and Capex.

History of VNFs and NFV

Service providers saw the potential for virtualized functions to simplify provisioning and ease service customization for their customers. In 2012, a group of service providers -- AT&T, BT, Deutsche Telekom, Orange, Telecom Italia, Telefónica and Verizon -- presented the concept of network functions virtualization (NFV) at the SDN and OpenFlow World Congress.

Although the two acronyms are sometimes used interchangeably, NFV and VNF mean different things. Individual VNFs are a primary component of an overall NFV architecture. NFV also includes NFV management, automation and orchestration (MANO) and NFV infrastructure.

NFV MANO acts as the framework for managing and orchestrating VNFs. NFV infrastructure includes compute, storage and networking components -- both software and hardware. This infrastructure provides the foundation for virtualized functions. All these NFV elements must then communicate with existing operations and billing systems.

A diagram of network infrastructure that includes individual VNFs.
In this diagram, VNFs form part of the overall network infrastructure, carrying out functions like load balancing and caching.

The European Telecommunications Standards Institute (ETSI) took charge of NFV development and standardization. In 2013, ETSI created the Industry Specification Group for Network Functions Virtualization (ISG NFV) to maintain NFV guidelines and specifications.

Many other standards groups and open source projects are also working to further NFV deployments. NFV adoption has been slow, however, due to a lack of accepted NFV standards. This lack of NFV standards results in potential interoperability issues with VNFs and their associated software.

This was last updated in September 2021

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