SDN architectures decouple network control and forwarding functions, enabling the network control to become directly programmable and the underlying infrastructure to be abstracted from applications and network services.
The OpenFlow protocol can be used in SDN technologies. The SDN architecture is:
Directly programmable: Network control is directly programmable because it is decoupled from forwarding functions.
Agile: Abstracting control from forwarding lets administrators dynamically adjust network-wide traffic flow to meet changing needs.
Centrally managed: Network intelligence is (logically) centralized in software-based SDN controllers that maintain a global view of the network, which appears to applications and policy engines as a single, logical switch.

The Agile Controller-Campus is a cloud management platform developed by Huawei for
campus networks. It cloudifies traditional network management functions using cloud computing technologies, and provides various features, such as multitenant management, plug and play, user access, cloud-based network planning, cloud-based PMI, and open APIs,
implementing flexible expansion of enterprise campus network services.

The explosion of mobile devices and content, server virtualization, and the advent of cloud services are among the trends driving the networking industry to re-examine traditional network architectures. Many conventional networks are hierarchical, built with tiers of Ethernet switches arranged in a tree structure. This design made sense when client-server computing was dominant, 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 patterns
The “”consumerization of IT””
The rise of cloud services
“”Big data”” means more bandwidth

SDN Application
SDN Controller
SDN Datapath
SDN Control to Data-Plane Interface (CDPI)
SDN Northbound Interfaces (NBI)

Centralized – Hierarchical – Distributed
The implementation of the SDN control plane can follow a centralized, hierarchical, or decentralized design. Initial SDN control plane proposals focused on a centralized solution, where a single control entity has a global view of the network. While this simplifies the implementation of the control logic, it has scalability limitations as the size and dynamics of the network increase.

Controller Placement
A key issue when designing a distributed SDN control plane is to decide on the number and placement of control entities. An important parameter to consider while doing so is the propagation delay between the controllers and the network devices, especially in the context of large networks. Other objectives that have been considered involve control path reliability, fault tolerance, and application requirements.

SDMN
SD-WAN
SD-LAN
Security using the SDN paradigm
SDN architecture may enable, facilitate or enhance network-related security applications due to the controller’s central view of the network, and its capacity to reprogram the data plane at any time. While security of SDN architecture itself remains an open question that has already been studied a couple of times in the research community,[48][49][50][51] the following paragraphs only focus on the security applications made possible or revisited using SDN.
Group Data Delivery Using SDN
Group Data Delivery (RGDD).