An Introduction to Software Defined Networking

Traditional Networking usually relies on fixed function network devices, eg. Switch, Router, MPLS switch, FC Switch, FCoE switch, Ethernet Switch. All these have the specific function and operate in coordination with each other to make your network work. It is faster because most of the functions are implemented as hardware constructs hence fast. The only “problem” being flexibility. Which is more hyped then true because of non-technical reasons.

Traditionally all switching hardware and software have been proprietary with not much of APIs exposed for provisioning. Even though they are exposed it usually works well with Proprietary Provisioning software which cant be changed swiftly according to the user(at least not if they have a small wallet).

Software Defined Networking on the other hand as I look at it is adding much programmability to the network. This could not be done on fixed function switches as Hardware is not subject to rapid transitions(Barefoot Networks and Cavium are changing this). Hence the control plane or I would say the decision making part was offloaded to software. Which makes it slow but more flexible as it can be changed and can talk to applications in the much better way than a traditional switch. This helps people with a small wallet as they can take a white box switch install an OpenFlow(or any southbound SDN) based OS and build there own controller and use them to program the switch.

This all sounds very good, but  it does not work that well and has not been able to beat traditional networking solely because traditional networking is tried and tested and is lightning fast compared to SDN. On the other hand, software-defined networking has the bottleneck of software. In computing, the industry was Network along with Von-Neuman bottleneck are the two most famous bottlenecks, SDN just makes the bottleneck more with only added the advantage of programmability.

Let’s take a look at some of the features that define the SDN along with the benefits they promise to deliver.

SDN vs Legacy

Networks are built around equipment such as routers, switches, and firewalls. Both the control plane and the data plane are baked into these hardware devices. The control plane determines where the traffic is sent. The data plane forwards that traffic based on how the control plane is configured. Making changes to the network configuration requires new hardware and more configuration.  Legacy networks also do not respond efficiently to changing network condition. Today that is important as virtualisation and mobility work best on dynamic networks.

SDNs take a play out of the server virtualisation playbook and insert an abstraction layer. This layer separates the control plane from the data plane. SDN effectively decouples the hardware from the software layer. This separation makes network virtualisation a reality because you are no longer executing control roles from the hardware devices. Legacy networks take time and effort to modify. SDNs promise administrators the ability to shape the network any way they want. The SDN also gives administrators the ability to set the rules and controls through a software interface.
Network administrators will embrace SDN because it allows for granular control of network traffic. It also promises to decrease reliance on hardware with proprietary firmware to perform these functions.

Primary Benefits

As I mentioned earlier, the SDN gives the administrator more control over how data flows along the network. It also allows them to change the network traffic rules on the fly. This saves both time and money. Let’s look at a few more benefits:

Centralized Provisioning – Because SDN is an open-source product, it will work with hardware across many vendors. Today one may standardize on Cisco hardware because it works well together. One can add hardware from other vendors, but that often makes the deployment and management of those assets a more complex. SDN moves the management layer to a software interface that promises to support hardware from any vendor.

Improved Security – Virtualization has made networks more complex and challenging for IT managers. Virtual machines come and go. That makes applying firewall and policies a challenge. Add mobile products like tablets, phones and  BYOD, and your security problems escalate quickly. The SDN controller gives the administrator a central point from which to enforce and distribute security policies.

Read More: 4 Security Tips For Implementing BYOD

Cloud Support – Whether you have migrated some or all of your services to the cloud, it is here to stay. SDN will help companies extend the data centre infrastructure to support various cloud environments without having to worry about the underlying protocols. This will allow them to connect various cloud services for their users and make hybrid cloud creation a lot easier.

Improved Content Delivery –  Not only is the number of content increases, but users are demanding it across all devices. Much of this content is in high definition. Companies like Netflix have benefited from new streaming technology that allows this rich content to be cached on the edge of the network. SDN provides the responsiveness that is required to deliver this content to the user.

Hardware Savings – SDN will not commoditize all hardware, but it will certainly reduce vendor lock-in. Moving the intelligence to the SDN controller allows IT to use less expensive hardware.


The most significant advantage of SDN today is that it is still mostly unproven. A lot of the benefits cited by companies with investments in the underlying technology are theoretical. That does not mean they will not work in practice, but it is too early to know for certain. Networking tools have been evolving now for more than 50 years. Whenever a new technology arrives and promises to overhaul the incumbent, there’s bound to be a few naysayers. I liken SDN to where the cloud was about a decade ago.
“At this time, there’s a lot to like about SDN – except the reality.” – Sam Masud

Another issue SDN will have to work through is its reliance on software. Hardware is expensive and takes time to configure. However, once optimized, it works for a long time. The software is buggy and requires developers to maintain it. The reliability of your network relies on the stability of the software managing it. Moving the intelligence from the hardware to the software layer sounds great in theory. Moreover, when it works, it will be a dream for administrators. However, when it goes down, that dream will turn into a nightmare.


Software Defined Networking (SDN) is predicted generate more than $ 400 billion in revenue. Several Companies such as Pica 8, Barefoot, Coarsa and, Amdocs to name a few are focused towards leveraging the principles of SDN to cleverly solve and introduce use cases related to internet ossification problem. Many well-established companies like Nuage from Nokia, Cisco, Blue planet from Ciena are some of the products related to the SDN-based orchestrator.

With so many companies investing in SDN and Network Function Virtualization (NFV) and so much of revenue to be tapped, I believe that SDN will most definitely go to prevail the industry. Because none of the recent past technologies (For ex: GMPLS) has captured the attention of Industry as did by SDN.

The above statements are just my opinion on the trend of SDN is going through. It may prove to be wrong or right. Nonetheless, for now, I do not see any major flaws and challenges in adapting SDN thus my answer is It has bright future.

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