Software-defined Networking (SDN) is the technology that separates the control plane management of network devices from the underlying data plane that forwards network traffic. 

Software-defined Networking (SDN)
Fig - Software-defined Networking (SDN)

For example, it promises to reduce the complexity of statically defined networks make automating network functions much easier, and allow for simpler provisioning MD management of networked resources, everywhere from the data center to the compose wide area network. SDN is a technique for a network that network nodes manage through programming, rather than traditional system administration methods, SDN will become important as IoT matures and its demands on the network increase. 

What is Software Defined Networking (SDN)

Software-defined Networking (SDN) is a function of computer networking that allows network administrators to govern network services through abstraction of lower-level purposes. SDN means responding to the fact that the static formation of conventional networks doesn't support the dynamic, scalable computing and storage needs of more radical computing environments such as data centers. This is done by demerging the system that makes decisions about where traffic is sent (the control plane) from the lurking systems that forward traffic to the selected destination (the data plane). 

SDN facilitates security benefits. A customer can divide a network connection between an end-user and the data center and have different security settings for the various types of network traffic. A network could have one public-facing, low-security network that does not touch any sensitive information. Another segment could have much more fine-grained remote access control with software-based firewall and encryption policies on it, which allow sensitive data to traverse over it. "For example, if a customer has a group it doesn't feel is all that mature with regards to security, via the SDN controller you can segment that group off away from the critical high-value corporate traffic. 

Different Types of SDN 

In this SDN, a virtual overlay network is created between vSwitches. The traffic paths between switches run over a traditional routed/switched network, or perhaps a switched fabric network. Because it relies on vSwitches as the overlay network endpoints, it is primarily a data center SDN solution. 

Deep SDN is a method of controlling packet forwarding behavior, one that can perform policy routing without complex combinations of protocols, as is required in shallow SDN. The logically centralized controller is able to see the entire network topology and make smarter decisions about the paths to use for each traffic type.