Demystifying Software-defined Networks Part I: Open SDN Approach

Javier Guillermo By Javier Guillermo September 5, 2017

The joke goes around that the true meaning of Software Defined Networking (SDN) is “Still Don’t Know”.  In short, SDN is a technology that allows network administrators to no longer be reliant on static architecture of traditional hardware/networks, but freed to centrally and dynamically manage the network via open, programmatic interfaces.  This is accomplished by separating the control plane (the system that decides where the network traffic will go) from the data plane (the systems that forward the traffic onto their destination).

Software Defined Networking (SDN): Business Drivers

What’s driving the need to change from the transitional method of managing networks and move towards a SDN approach?  There are three key catalysts in the industry driving the need for network change as show in the graphic below.

SDN Business Drivers

Mobility, cloud, and IoT are three very real ways in which business is being digitally transformed and I will cover them in more detail in future blogs.

SDN, along with Network Function Virtualization (NFV) and other network virtualization technologies, are key to successfully transitioning to a data center that can adopt and deliver cloud solutions.  In this series of short blogs, I hope to give you some insights on topics important to better understanding SDN.

There are also three main ways to approach Software Defined Networking (SDN):

1. Open SDN

2. SDN by APIs

3. SDN by overlays

In this blog, I will be focusing on the Open SDN approach.  What is meant by Open SDN?  Both SDN and NFV technologies have a large open source community, committed to contributing to projects that promote open standards. As you see in the image below, separating the control and forwarding planes removes the controlling software from the device and onto a controller.  The device then handles the forwarding and data plane functions, while the controller handles the control plane functions.

Software Defined Networking_2

This approach tends to be focused around OpenFlow (OF), which is considered to be one of the first SDN standards, and allows a SDN controller to directly interact with network devices (routers, switches, etc.) as you see in the image below.  OF is just the protocol, so you could have Open SDN with other protocols if you choose.

This approach you see in the image below provides:

  • Simplified devices
  • A centralized controller
  • Enforcement of rules implemented by devices
  • Open environment for research and innovation
  • Interoperability
  • True network operating system
  • OF as the southbound standard protocol

Software Defined Networking_3


Check back for the next blog in the series where I will cover the SDN Approach by API.

Looking for more information on SDN and NFV? Check out NFV Operating Models – How to Mix Oil and Water (also known as IT Operations and Network Operations)

Javier Guillermo

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