What is NFV (Network Functions Virtualization)? Definition

Network Functions Virtualization (NFV) is the decoupling of network functions from proprietary hardware appliances and running them as software in virtual machines (VMs).

The different functions — such as firewalls, traffic control, and virtual routing — are called virtual network functions (VNFs).

NFV uses virtualized networking components to support an infrastructure totally independent of hardware. The standard resources of compute, storage, and network functions can all be virtualized and placed on commercial off-the-shelf (COTS) hardware like x86 servers. Having virtualized resources means that VMs can be given portions of the resources available on the x86 server. That way, multiple VMs can run on a single server and scale to consume the remaining free resources. This also means that resources are less often sitting idle and data centers with virtualized infrastructure can be more effectively used. Within the data center and the outside networks, the data plane and control plane can also be virtualized with NFV.

High-level NFV framework. Source: ETSI

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NFV vs SDN (Software Defined Networking)

NFV refers to the virtualization of network components, while SDN refers to a network architecture that injects automation and programmability into the network by decoupling network control and forwarding functions. In other words, NFV virtualizes network infrastructure and SDN centralizes network control. Combined, SDN and NFV create a network that is built, operated, and managed by software.

An SDN typically has an SDN controller, northbound application program interfaces (APIs), and southbound APIs. The controller allows network administrators to view the network and dictate behaviors and policies to the underlying infrastructure. Southbound APIs take information about the state of the network from that infrastructure and send it back to the controller, which is necessary to keep the network running smoothly. Applications and services use northbound APIs to communicate their resource needs to the controller.

The Benefits of NFV

Network operators who virtualize their network can save money, shorten the time-to-market for new or updated products, and better scale and adjust resources available to applications and services. Other benefits include:

Less Vendor Lock-in: Running VNFs on COTS hardware, which means organizations aren’t locked into proprietary, fixed-function boxes that take truck rolls and significant time and labor to deploy and configure.

Greater Resource Efficiency: A virtualized data center or other infrastructure is more efficient to operate because more can be done with less. Data center footprint, power consumption, and cooling requirements can all be reduced or kept the same, but with increased workload capacity. This is possible because a single server can run multiple VNFs at once, so not as many servers are needed to do the same amount of work. When network demand changes, an organization can update its infrastructure through software instead of doing another truck roll. The instances where an organization needs to physically update its network and data centers are significantly reduced.

Flexibility: Organizations can use the agility of NFV to quickly adapt to changing business requirements and new market opportunities. In other words, the time-to-market period is shortened because the network infrastructure can be changed to adequately support the organization’s new products. A network that has gone through NFV is also able to adjust quickly and easily to changes in resource demand as traffic coming to the data center increases or decreases. Scaling up and down in the number of VMs and the resources provided to them can be done automatically through SDN software.

Challenges Associated with NFV

Challenges around NFV are rooted in three components of the technology: the NFV manager (NFVM), VNFs, and the NFV infrastructure (NFV infrastructure (NFVI)). The three components are so tightly joined together that instead of the theoretical simplification for network operators, in practice it adds complexity and difficulty when deploying NFV at scale.

The Lean NFV has attempted to solve these problems by developing a new approach to NFV architecture.

“The complexity currently hindering NFV arises not from how any one of the above pieces is built, but instead from how they are woven together into an overall system,” the organization said in a 2019 white paper. “More specifically, the complexity arises when the NFV manager is integrated with the existing computational infrastructure, when VNFs are integrated with the NFV manager, and when the coordination is required between the various components of the NFV manager.”

The white paper goes on to say that the focus needs to be on simplifying the three points of integration so other elements of NFV designs can be innovated more freely.

One reason there is complexity in the components of NFV technology is because there have been multiple organizations trying to standardize them. This led to no single approach that has worked for the whole industry and no set of standards that stood out enough to be more heavily invested in or adopted.

History of Network Functions Virtualization

The concept of NFV originated from service providers who wanted to make adding new network functions or applications easier and faster. As mentioned, different service providers did not make one standards organization, and instead made several. Some service providers opted for an open source approach to developing a standard NFV architecture.

A notable standards organization is the European Telecommunications Standards Institute (ETSI), which was the first major organization to release an NFV standard in October 2013. The ETSI ISG NFV is a specifications group that has set standards for NFV management and network orchestration (MANO) and network orchestration (NFV MANO). ETSI is also instrumental in collaborative projects like OPNFV.