Virtually Networked: The State of SDN

We have all heard about hectic activity with several initiatives on network virtualization. The potpourri of terms in this space (SDN/OpenFlow/OpenDaylight etc.) are enough to make one’s head spin. This article will try to lay out the landscape as of the time of writing and explain how some of these technologies are relevant to independent broadband service providers.

In the author’s view – Software Defined Networking (SDN) evolved with the aim of freeing the network operator from dependence on networking equipment vendors for developing new and innovative services and was intended to make networking services simpler to implement and manage.

Software Defined Networking decouples the control and data planes – thereby abstracting the physically architecture from the applications running over it. Network intelligence is centralized and separated away from the forwarding of packets.

SDN is the term used for a set of technologies that enable the management of services over computer networks without worrying about the lower level functionality – which is now abstracted away. This theoretically should allow the network operator to develop new services at the control plane without touching the data plane since they are now decoupled.

Network operators can control and manage network traffic via a software controller – mostly without having to physically touch switches and routers. While the physical IP network still exists – the software controller is the “brains” of SDN that drives the IP based forwarding plane. Centralizing this controller functionality allows the operator to programmatically configure and manage this abstracted network topology rather than having to hand configure every node in their network.

SDN provides a set of APIs to configure the common network services (such as routing/traffic management/security) .

OpenFlow is one standard protocol that defines the communication between such an abstracted control and data plane. OpenFlow was defined by the Open Networking Foundation – and allows direct manipulation of physical and virtual devices. OpenFlow would need to be implemented at both sides of the SDN controller software as well as the SDN-capable network infrastructure devices.

How would SDN impact an independent broadband service providers? If SDN lives up to its promise, it could provide the flexibility in networking that Telcos have needed for a long time. From a network operations perspective, it has the potential to revolutionize how networks are controlled and managed today – making it a very simple task to manage physical and virtual devices without ever having to change anything in the physical network.

However – these are still early days in the SDN space. Several vendors have implemented software controllers and the OpenFlow specification appears to be stabilizing. OpenDaylight is an open platform for network programmability to enable SDN. OpenDaylight has just released its first release of software code – Hydrogen and it can be downloaded as open source software today. But this is not the only approach to SDN – there are vendor specific approaches that this author will not cover in this article.

For independent broadband service providers wishing to learn more about SDN – it would be a great idea to download the Hydrogen release of OpenDaylight and play with it – but don’t expect it to provide any production ready functionality. Like the first release of any piece of software there are wrinkles to be ironed out and important features to be written. It would be a great time to get involved if one wants to contribute to the open source community.

For the independent broadband service providers wanting to deploy SDN – it’s not prime-time ready yet – but it’s an exciting and enticing idea that is fast becoming real. Keep a close ear to the ground – SDN might make our lives easier fairly soon.

[Editor’s Note; For more great insight from Kshitij about “SDN” and other topics , please go to his website at]

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