Software Defined Networking (SDN) separates the software from the hardware in a network – and so uses virtualisation in the network as well. A controller enables central control of the network components and automated, dynamic routing of data flows. The fourth and final part of our series on automated networks.

When discussing modern networks, you often hear the terms NFV (Network Functions Virtualisation) and SDN (Software Defined Networking). Both these methods can be combined well with each other to create flexible and automated networks. But SDN goes rather further than NFV.

Network Functions Virtualisation (NFV)

NFV enables virtualisation of the network appliances or the network functions. This means NFV converts physical network services, e.g. routers, firewalls, DNS, intrusion detection systems or controllers for providing applications, into virtual network services which can be managed automatically. Since NFV replaces this proprietary hardware with software, the network functions run virtually, on inexpensive standard servers.

So NFV does not just reduce costs, but also accelerates the provision of network functions. It enables flexible services, because virtualised network functions can be started and moved as required on decentralised standard network hardware. It is also possible to assign resources flexibly and dynamically. Whereas NFV concentrates on the virtualisation of physical network appliances or functions, Software Defined Networking focuses on centralising the network intelligence.

SDN: Software Defined Networking

With SDN, the system software is decoupled from the network hardware by separating the levels for network data analysis and control of the network configuration (control plane) and for transporting data in the network (data plane) from each other. This means it is possible for the analysis and control planes to be completely virtual. Physical network access is not required. The control plane generally communicates with the individual hardware components (routers, switches etc.) via an Application Programming Interface (API). The data plane carries out the instructions from the control plane. These could be, for example, rules for routing the data packets. The network controller is generally centralised and can control and manage numerous different network components such as routers or switches.

The difference between NFV and SDN: NFV concentrates on virtualising and optimising the provision of network functions, whereas SDN decouples the network intelligence in order to create more intelligent routing architecture which can then be automated. The goal is to optimise the data transport. Potential application areas for SDN are data centres, service provider networks, enterprise WANs (Wide Area Networks) and campus networks.

Central administration and automation

Since SDN unites the control plane for all network components, the administrator has an overview from a central point. Furthermore, tasks in the whole network are simpler to automate with a single script. SDN automates provisioning of required network resources based on parameters such as application type, security requirements or QoS (Quality of Service) requirements. The latter enables specific traffic types to be identified – e.g. speech and video – and prioritisation of network resources. By using software and also AI, this enables the data flow in the network to be guided intelligently and efficiently, and controlled automatically depending on the network load or latency.

Here is an overview of the most important advantages:

  • Rapid provisioning of network functions and resources
  • Central creation and distribution of security guidelines for all devices
  • Simpler network operation thanks to centralised orchestration
  • A higher degree of automation reduces costs
  • Dynamic data routing according to application requirements (bandwidth, latency etc.)
  • Simple implementation of new network concepts


In its ideal form, SDN works completely autonomously: automatically and independently configuring network services which adapt dynamically to each application. The entire IT infrastructure operates detached from the hardware and so is elastic in all directions. All central components of the network – servers, storage, switches/routers and security – are all available at any time, in exactly the amount and form in which they are currently needed. So challenges due to peak loads are consigned to history, as is the purchasing of expensive and only partially-utilised hardware resources.

But we will have to wait a few more years until SDN becomes the standard in businesses and cloud providers. There is a lot of preliminary work to be done before SDN can be implemented. Companies need orchestration tools for software systems and must also be able to program software components themselves. Furthermore, there are to date too few products which support open SDN protocols such as OpenFlow. OpenFlow enables virtual networks to be managed even beyond provider boundaries. There are already enough software controllers for this. But there are currently few OpenFlow-compatible hardware components. This is because, for the manufacturers of network components, SDN results in proprietary hardware (e.g. switches), losing significance. In contrast, SDN controllers and the appropriate management tools become more important.

Conclusion: SDN is a step in the right direction towards open, more flexible, efficient and programmable network infrastructure solutions.

The articles “Network automation – an introduction“, “Application examples for automated networks” and “Challenges in network automation” have already appeared in our blog series.

Questions? Just ask!

I am Alexander Zagler from the HCD sales team. I will be happy to advise you or assist you with any questions. You can phone me on +49 89 215 36 92-0 or reach me using our contact form.

Contact us

Just ask!

I am Alexander Zagler from the HCD sales team. I will be happy to advise you or assist you with any questions. You can phone me on +49 89 215 36 92-0 or reach me using our contact form.

Contact us