Software Defined Network: an overview

Software Defined Network: an overview

what is an sdn

SDN is an innovative approach to design, implementing, and managing networks that separate the network control and the forwarding process for a better user experience. The architecture enables the network to be intelligently and centrally controlled or programmed, using software applications 1.

An SDN should be directly programmable, agile, centrally managed, programmatically configured, open standards-based, and vendor-neutral.

Actually, the controller plane, which is the centralized intelligence of SDN, commonly uses OpenFlow protocols to command switches, and routers 2.

OpenFlow system was initially created at Stanford University now under dynamic gauges improvement through the Open Networking Foundation (ONF). Open Networking Foundation(ONF) defined that the OpenFlow protocol is based on SDN layered architecture3.

sdn architecture

In a normal network architecture, the implementation, configuration, and troubleshooting require a skilled engineer to maintain and manage the network, incrementing the operational costs involved. An SDN separates the routing and forwarding decisions of networking elements from the data plane, replacing the hardware components with software components.

It is possible to divide the core architecture SDN into three layers2:

  • Application plane
  • Control plane
  • Data plane

The application plane defines rules and offers different services such as firewall, access control, IDS/IPS, quality of service routing, proxy service, and monitoring balances.

The control plane is an abstraction of the network topology and it can be considered the brain of the SDN managing the flow of traffic through the network.

The data plane provides networking devices such as physical /virtual switches, routers, and access points and takes care of all data activities such as forwarding, fragmentation, and reassembly.


OpenFlow protocol is based on SDN layered architecture, it is in between the control plane and forwarding plane as communication protocol. As said before is implemented in the switches and divides the data path from the control path.

There are two types of Openflow switches: Openflow only switches and Openflow hybrid switches that use both Openflow and normal Ethernet Operations3

The communication between the controller and the switch can be either run over Transport Layer Security (TLS) or without an encryption mechanism, depending on the security needs and deployments2.


Nowadays, the typical network architecture can’t satisfy companies’ demands. The SDN architecture, based on Openflow, abstracts the above layers of the network infrastructure allowing the network to become programmable and manageable on a big scale, the SDN can increase the management, scalability, and network agility4.

The future of networks will be based more and more on software so the SDNs will transform the static network into flexible and programmable platforms, to allocate resources dynamically and manage easier the networks4.


  1. . A Survey on the Architecture, Application, and Security of Software Defined Networking. Nisar Kasif, Ian Welch, Rosilah Hassan, Ali Hassan Sodhro, Sandeep Pirbhulal. DOI:10.1016/j.iot.2020.100289, September 2020, Internet of Things .
  2. Software-defined networking (SDN): a survey. Kamal Benzekki, Abdeslam El Fergougui and Abdelbaki Elbelrhiti Elalaoui. s.l. : Wiley Online Library, 7 February 2017, Vols. Security Comm. Networks 2016; 9:5803–5833. DOI: 10.1002/sec.1737.
  3. Software Defined Networking: Research Issues, Challenges and Opportunities. Shailendra Mishra, Mohammed Alshehri. s.l. : Indian Journal of Science and Technology, February 2017. DOI: 10.17485/ijst/2017/v10i29/112447.
  4. Software-Defined Networking:. ONF White Paper, April 13, 2012.


  • Genny Aprea

    Genny Aprea, Ingegnere delle Telecomunicazioni laureato presso la Federico II, dopo il periodo di ricercatore associato presso CNR ISASI è stato assunto in Kineton in qualità di Broadband Technical Expert di Kineton.

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