Software-Defined Networking – SDN


Software Defined Network


In Simple layman terms physical separation of the network control plane from the forwarding plane, and where a control plane controls several devices and direct the data plane that how forwarding devices will function into the network.

Software-Defined Networking (SDN) is an emerging architecture that is dynamic, manageable, cost-effective, and adaptable, making it ideal for the high-bandwidth, dynamic nature of today’s applications. This architecture decouples the network control and forwarding functions enabling the network control to become directly programmable and the underlying infrastructure to be abstracted for applications and network services. So for better understanding of the above topic first of all we should know the basic difference between Control Plan and Data Plane because every network appliance works on these 2 architecture and The Control Plane, Data Plane in Networks is the heart core DNA in today’s networking hardware to move IP packets from A to Z.


Control Plane – The control plane is the part of a network that carries signaling traffic and is responsible for routing. Control packets originate from or are destined for a router. Functions of the control plane include system configuration and building adjacency between all the routers which ensure end to end routing takes place. Example Routing protocol, network middle box configuration.

Data Plane – The data plane (sometimes known as the user plane, forwarding plane, carrier plane or bearer plane) is the part of a network that carries user traffic. The data plane, the control plane and the management plane are the three basic components of a telecommunications architecture. The control plane and management plane serve the data plane, which bears the traffic that the network exists to carry. Example – CEF, Ip Forwarding, L2/3 Switching.

Example – Control Plane =>Our planning stage, which includes learning which paths the buses will take, is similar to the control plane in the network. We haven’t picked up people yet, nor have we dropped them off, but we do know the paths and stops due to our plan. The control plane is primarily about the learning of routes.

Data Plane => actually moving the packets based on what we learned. The data plane is the actual movement of the customer’s data packets over the transit path we learned in the control plane stage.

In conventional networking, all three planes are implemented in the firmware of routers and switches. Software-defined networking (SDNdecouples the data and control planes, removes the control plane from network hardware and implements it in software instead, which enables programmatic access and, as a result, makes network administration much more flexible. Moving the control plane to software allows dynamic access and administration. A network administrator can shape traffic from a centralized control console without having to touch individual switches. The administrator can change any network switch’s rules when necessary — prioritizing, de-prioritizing or even blocking specific types of packets with a very granular level of control.





Why Separation of Control Plane and Data Plane is important.

  • One reason is that by separating the control plane and data plane each can be evolved and developed independently in particular software controlling the network can evolve independently the hardware that means one can buy router switches middle boxes so forth deploy them into network and not be bound by the capability a software that shipped with the hardware at that particular time.
  • To separate the Control plane and data plane that it allowed the network to be allowed to be controlled from a single high level software program. So higher program could control the behavior the entire network and in doing so not only is it easier to be said about behaviour the network but it’s also to debug to check the behaviour.
  • Load balancing is required every time accordingly to traffic behaviour at peak time but separating control plane from data plane technology can easily allocate the resources from one end to another end.



The need of the new network Architecture – The explosion of mobile devices and content, server  virtualization, and advent of cloud services are among the trends driving the networking industry to reexamine traditional network architectures. Many conventional networks are hierarchical, built with tiers of Ethernet switches arranged in a tree structure. This design made for simple client-server architecture is acceptable for small customer but such a static architecture is ill-suited to the dynamic computing and storage needs of today’s enterprise data centers, campuses, and carrier environments. Some of the key computing trends driving the need for a new network paradigm include:


  • Changing traffic pattern – Within the enterprise data center, traffic patterns have changed significantly. In contrast to client-server applications where the bulk of the communication occurs between one client and one server, today’s applications access different databases and servers which are resides in data centers across globe. At the same time, users are changing network traffic patterns as they push for access to corporate content and applications from any type of device (including their own), connecting from anywhere, at any time.
  • The rise of the cloud services – Enterprises are keen to opt both public and private cloud services, resulting in unprecedented growth of these services. Enterprise business units now want the agility to access applications, infrastructure, and other IT resources on demand model. To add to the complexity, IT’s planning for cloud services must be done in an environment of increased security, compliance, and auditing requirements, along with business reorganizations, consolidations, and mergers that can change assumptions overnight. Providing self-service provisioning, whether in a private or public cloud, requires elastic scaling of computing, storage, and network resources.
  • Big Data Means more Bandwidth – Handling today’s “big data” or mega datasets requires massive parallel processing on thousands of servers, all of which need direct connections to each other with bigger bandwidth requirement.





SDN Controller – An SDN Controller platform typically contains a collection of “pluggable” modules that can perform different network tasks. Some of the basic tasks including inventorying what devices are within the network and the capabilities of each, gathering network statistics, etc. Extensions can be inserted that enhance the functionality and support more advanced capabilities, such as running algorithms to perform analytic’s and orchestrating new rules throughout the network.

SDN Technology will help to reduce the cost of managing Large Enterprise/Data Centre Network because instead of putting every Layer 2 switch into the network of any good vendor which cost around $5K, Now Network Team can place any commodity (Bare Metal) switch in between Large Server Farm and switches for connectivity which cost around $1K. Hence if you have to procure 10K switches across 5 Data Center it will save you approx. $40Mn cost and it is also easy to manage all the switches through SDN Controller. There are several more advantages also in respect to manipulating Network traffic pattern which also gives

There are several emerging companies who started offering SDN solutions into the market Like Cisco, HP, Juniper, Ericsson, Big Switch Networks, Inflobox, LineRate Systems , Cumulus Networks, Plum grid, IBM, Dell, Broadcom, Adara Network, Extreme Network, NEC, Netronome, Nicira, Pertino and there are several startup companies also into this cutting edge technology who all are putting their effort on development of SDN platform.

The Open Networking Foundation (ONF) is a nonprofit, mutually beneficial trade organization, funded by prominent companies such as, FacebookGoogleMicrosoftVerizon and Yahoo! aimed at improving networking through software-defined networking (SDN) and standardizing the Open Flow protocol and related technologies.

OpenFlow® is the first standard communication interface defined between the controls and forwarding layers of an SDN architecture. Open Flow® allows direct access to and manipulation of the forwarding plane of network devices such as switches and routers, both physical and virtual (hypervisor-based).Open Flow-based SDN technologies enable IT to address the high-bandwidth, dynamic nature of today’s applications, adapt the network to ever-changing business needs, and significantly reduce operations and management complexity.

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