Today, the SDN, NFV and SD-WAN approaches are disrupting traditional network systems. They are initiating a “real change” in enterprise network infrastructures with promises of cost reduction, agility, flexibility, the speed of implementation and adaptation. Trends follow one another and strongly impact the very design of the network. SDN, NFV and SD-WAN have become basic building blocks to better prepare its network for the challenges of today and tomorrow. But we still have to understand these different concepts.

SDN (Software-defined networking)

SDN makes it possible to make the operation of the network devices programmable and to control them via a central element called a controller. Initially initiated on university campuses, the SDN is today the subject of a standard defined by the Open Network Foundation (ONF). Reflections on SDNs arose from a major problem faced by the network industry. It was becoming increasingly difficult to build and administer large-scale IP / Ethernet networks.

Logically, the SDN aims to separate the network control plan from the data plan. Thus, in a traditional network, when a packet arrives at a switch of the network, the rules incorporated in the firmware thereof govern how to transfer this packet. Each packet is thus sent to the same destination.

In an SDN scenario, the rules governing the handling of packets reach the switch from a controller, an application that runs on a server. The switch then queries the controller for rules about packet management.

Thus, thanks to the SDN, the network administrator can, at his will, modify the rules of a network equipment (switch, router …) by setting priorities, or even by blocking certain specific types of packets. The level of control is therefore very granular and can also be programmed.

In multi-tenant architecture scenarios for Cloud Computing, this approach is particularly relevant. But, the cases of deployment of SDN are not limited to these architectures alone.

In summary, the SDN allows the administrator to use less expensive equipment and strengthen his control of network traffic flows. OpenFlow open protocol was initially the pathway for interaction between network devices and the controller, but other protocols have also emerged.

NFV ( Network function virtualization)

The NFV has been standardized by the Industry Specification Group (ISG) of the ETSI (European Telecommunications Standards Institute). It was born from the desire to accelerate the deployment of new network services. A will that was limited, in a way, by the hardware.

NFV is a way of reducing costs and accelerating the deployment of services for network operators by decoupling functions (firewall, data encryption …) from dedicated hardware and transferring them to virtual servers. . Hence the term “virtualization” in the acronym NFV.

The relationship between NFV and SDN

SDN and NFV are not integral parts of each other. If the two notions are very different, they are none the less related. NFV can thus be implemented without the need for an SDN, although these two approaches can be combined to provide greater added value.

The objectives of NFV can be achieved by using non-SDN mechanisms, building on the techniques currently used in many data centers. But approaches based on the separation of control and data transfer plans, as proposed by the SDN, can improve performance, simplify compatibility with existing deployments, and facilitate operation and maintenance procedures.

NFV is able to support SDN by providing the infrastructure on which the SDN software can be run. In addition, the NFV aligns closely with the SDN’s objectives for server and switch usage.

SD-WAN (Software-defined wide-area-network)

SDN extends beyond the company’s data center and campus to WAN (Wide Area Network). This is called SD-WAN, which exists via many products of actors such as those proposed by the operator Colt.

The SD-WAN allows companies to deport services, such as email or web browsing, over the Internet to relieve the more expensive MPLS links, still reserved for critical or sensitive applications.

It fuels the greed of companies but also telecom operators. Indeed, with the upcoming arrival of 5G (commercially planned for 2020), the SD-WAN is seen as the future major evolution in the field of telecom.

But, it is also relevant for organizations with a multi-site network and exploiting MPLS (MultiProtocol Label Switching) links that are not optimized according to the uses that are made of them. SD-WAN provides flexibility where MPLS is rigid. It also provides better responsiveness to maintain the desired QoS and reduces costs compared to MPLS.


Virtualization in networks has given rise to Software Defined Storage (SDS), SDN, NFV and SD-WAN. But, the trend towards ever more virtualization has not stopped in such a good way. The variations are going well with a move to the SDx for “Sofware Defined Everything”.

In all these cases, it is a matter of moving the intelligence of the hardware to software that can be run on standardized equipment, so inexpensive.