SDN: Software Defined Networking

- SDN, Software Defined Networks and Networking provide a key technique to be used for the next generation networks. Using software defined techniques significant advantages can be gained.

SDN Tutorial Includes

Software defined networking, SDN is a telecommunications network architecture that provides the promise of significant improvements in the network performance.

Using software defined networking the is possible to make the network more dynamic, manageable, cost-effective, and adaptable.

The key behind software defined networking is that the SDN architectures decouple network control and forwarding functions. This enables the network control to become directly programmable. As a result the underlying network infrastructure can be abstracted from applications and network services.

Software defined networking background

The huge growth in mobile devices and the data they use along with server virtualisation and the use of cloud services as well as many other changes have caused many in the telecommunications industry to re-examine the network architectures that have been used for many years.

Many of these networks are tiered and have a very hierarchical structure with many Ethernet switches arranged in a tree structure.

This form of static telecommunications network design topology made much sense when client serving computing was the main method of working. However this form of network architecture is ill suited to the dynamic computing and storage needs that have evolved around new computer usage scenarios with data centres, carrier environment and campuses.

To meet these needs a far more flexible and agile network architecture was needed.

Software defined networking basics

With software providing a means by which much functionality can be provided, its adoption into networking enables many features to be run using software rather than hardware.

Using software defined networking, the network control is detached from the elements of the network that providing the data forwarding.

By structuring the network architecture in this way into accessible computing devices, enables the underlying infrastructure to be abstracted for applications and network services to treat the network as a logical or virtual entity rather than a large number of tightly bound devices.

The diagram below shows a logical view of software defined networking architecture with the three layers: application layer; control layer; infrastructure layer.

The basic concept and framework for software defined networking
Software defined networking framework

The intelligence for the network is typically contained within software defined networking controllers which are able to control the complete network. In this way, the whole network can be treated by the applications and policy entities as a single large logical switch.

By adopting this software defined networking approach, the whole network can be controlled from a single point. This greatly simplifies the design, operation and updates. SDN also simplifies the network devices themselves as they only need to interface with a single control standard and not the many protocol standards they would otherwise need to process.

Open Networking Foundation & SDN

The Open Networking Foundation, ONF is an industry organisation that has been set up with the aim of promoting and adoption of Software Defined Networking through open standards development.

The ONF draws its members from industry and coordinates the activities of software defined networking standardisation. It has developed the OpenFlow protocol which structures the communication between the control planes and data planes of a software defined network.

The OpenFlow protocol is being rolled out and utilised in a number of software defined networks to provide a common interface allowing operators to interface to various elements.

Difference between SDN & NFV

Software defined networking and network functions virtualization are very closely linked as they both have software as the key, but they are not the same.

The two techniques can be used together or separately. The main points of each are summarised below so that both SDN and NFV can be evaluated with their similarities and differences.

  • SDN, Software Defined Networks:   SDN separates the network control and forwarding planes and provides a central view for more efficient implementation and running of the network services.
  • NFV, Network Functions Virtualisation:   NFV focuses on optimising the network services themselves. This technique decouples the network functions from proprietary hardware, placing them on more generic servers or computers so these functions can run in software to provide more flexibility for operation, changes and updates.

Although the two are similar the difference between SDN and NFV means that they are not the same and can both techniques be used on the same network to provide significant benefits.

By Ian Poole


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