(ONF) defines SDN as follows:
an emerging architecture that is dynamic, manageable,
cost-effective, and adaptable, making it ideal for the
high-bandwidth, dynamic nature of 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.An SDN controller possesses a “global” view of the entire
network. It knows about all the network elements that
constitute the network, the best paths between them, and
other potential routes. As indicated in the ONF SDN
definition, SDN is a network architecture that separates
the control and data planes for network devices and
provides centralized management. There are two widely
popular controllers:
OpenFlow: The ONF manages this standard used for communication
between the SDN controller and managed network devices.
OpenDayLight: The Linux Foundation (LF) manages this standard,
which uses OpenFlow to manage network devices.As shown in Figure 17-23, SDN involves three layers:
application layer, control layer, and infrastructure layer.
Figure 17-23 Software-Defined Networking:
Layered Architecture