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Guide to SDN, SD-WAN, NFV & VNF

SD-WAN and Network Functions

A deluge of buzzwords in the field of the networking industry often creates confusion for the ordinary reader. So many acronyms, similar to one another, and even the core technologies behind each one of these acronyms builds into another, with overlapping themes, which adds further confusion into the picture. It becomes difficult to understand their working and functionalities in a clear and distinct way. Although these concepts are related to one another, they are distinct in their own way. That is why they require special attention with a distinct explanation for a proper understanding. For that purpose, special focus is given to the following terms.

Software Defined  Network (SDN)

SDN is an architectural network in cloud computing, network security and intent based networking with the key principle of introducing physical separation between the network control plane and the forwarding plane. The control plane is responsible for handling traffic. Whereas the data plane refers to the flow of data between the network nodes. By separating the network planes, SDN architecture efficiently manages to achieve significant benefits including fault tolerance, central management, redundancy, network’s global view, hardware independence and agility in implementation and distribution. It also incorporates interoperability.

Software Defined – Wide Area Networking (SD–WAN)

SD–WAN is a newly emerged technology rapidly governing the network market. It incorporates key principles of SDN into wide area networking. It further extends these key SDN principles to accommodate the practical realities of wide area networking in innovative ways by providing enhanced service quality over unpredictable links and minimising long distance delays from one node to another.  In SD-WAN, reliability over the dedicated hardware circuits is minimised, and we can achieve the same networking performance without relying on pre-defined hardware setups. It chooses an optimal path for incoming traffic through software defined networking from multiple transport sources like mobile networks, data sources and broadband, etc. Each connection request is assigned with a specific bandwidth and latency through specific routing according to the needs of the application. It manages multiple network connections in economical ways, beneficial in a business perspective, by giving the same performance as the multi-protocol label switching (MPLS) technique provides in wide area networking (WAN).

Network Functions Virtualisation (NFV)

NFV is an architecture for virtualisation of network functions that incorporates the running of SDN functions without relying on a hardware platform. It is an infrastructural platform that is implemented for the orchestration of virtual network functions (VNFs). This concept has been used with data centres for a long time. But in recent times, with the emergence of SD–WAN, NFVs are coupled with software defined – WAN to make use of its advantages in remote branches.

Virtual Network Functions (VNF)

Virtual network functions are virtualised network services  that firmly run on open computing platforms. These virtual network functions include individual network services such as firewalls, network address translation (NAT), virtualised routers and optimisation of WAN. Most VNFs run over virtual machines. For instance, a routing VNF incorporates all the router functions, but it only runs on generic hardware in a software only form. It can do so alone or running along with other VNFs. These virtual network functions (VNFs) are administrated and orchestrated within an NFV network architecture.

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Core goals of all these technologies

These above-mentioned technologies and architectures account for the implementation of the network by virtualisation and software-only solutions. These software-based solutions are highly scalable, flexible and easy-to-upgrade. In contrast, previous practices of network implementation were based on dedicated single purpose hardware distributed solutions. But the emergence of SDN, SD-WAN, NFVs and VNFs have changed the paradigm. On a further note, all the four concepts offer the same benefits with a shared objective, which can be inferred by their core goals defined below:

  1. Focuses on software and the cloud

These are based on running software-based functions remotely by offering central control from a central orchestrator. It is important to be noted here that these software instances that are running on the cloud are also functioning as the cloud at the same time.

  1. Future proof

Software instances such as VNFs are capable of being downloaded from a central orchestrator at any time for upgradation.

  1. Reduction in enterprise costs

These are capable of being deployed to remote locations by deploying generic hardware. They control all the network functions and services remotely by downloading the VNFs. This accounts for a reasonable reduction in enterprise costs by centrally controlling the software defined solutions remotely.

  1. Agility

Software defined solutions provide a set of controls from the orchestrator via a single click, for example, in the form of upgrading, downloading, activating, de-activating, moving, removing and scaling up/down of a VNF.

  1. Interoperability

All these technologies use open standards to run the network functions on general hardware, like programmable units.

  1. Widespread availability

With the removal of the control plane (decision making panel) from the data plane (forwarding hardware), many of the network problems are resolved, for example, node failures, link failures and many other network problems, which gives rise to maintaining the network flow. In the case of any outage occurrence into the data plane that affects it, data flow can be redirected by the control plane to some other path. Even in the case of an outage occurrence in the control plane,  no harm is done in forwarding the data plane.

Shared Goals

On a further note, NFV and SD–WAN make a perfect combination, being highly complementary.  In cloud data centres and enterprises, both these solutions are very easy to deploy as virtual services (VNFs) or a service chain of SD–WAN. Additionally, cloud services can be delivered across the whole enterprise to all its remote localities by using NFV with SD–WAN due to its typical nature of service deployment in the cloud.


In general, SDN, SD–WAN, NFVs and VNFs offer shared principles with common goals. As they are complementary in their implementation and technological concepts, all these architectural designs are very beneficial to be used in conjunction with each other. This is not a matter of choosing between one of these technologies and architectures,  the most important determination should be using the one that can deliver maximum benefit to the network.

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Copyright by Digital Carbon. All rights reserved.

Copyright by Digital Carbon. All rights reserved.