Virtual network functions (VNFs) are virtualized tasks formerly carried out by proprietary, dedicated hardware. VNFs move individual network 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 or network address translation (NAT) and can run as virtual machines (VMs).
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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.
Benefits of using VNFs
Traditionally, new services and network functions are installed manually, configured along with their dedicated hardware devices or boxes. But with service chaining, for example, if certain functions need to be linked to perform a desired sequence, each dedicated device needs to be manually cabled together accordingly. Since VNFs virtualize those functions, eliminating the need for specific hardware, new functions can be deployed as VMs more quickly.
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, since VNFs replace physical hardware. These benefits also result in reduced operational and capital expenditure.
History of NFV and VNFs
Service providers saw the potential for virtualized functions to simplify provisioning and make service customization for their customers easier. 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 architecture also includes NFV management, automation and orchestration (MANO) and NFV infrastructure. MANO acts as the framework for managing and orchestrating VNFs. NFV infrastructure includes compute, storage and networking components -- both software and hardware -- used as the foundation for virtualized functions. All of these NFV elements must then communicate with existing operations and billing systems.
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.