Software Defined Networking (SDN)

- The Traditional Wide Area Network (WAN)

A wide area network (WAN) is a telecommunications network that extends over a large geographical distance for the primary purpose of computer networking. WANs are often established with leased telecommunication circuits. Business, education and government entities use WANs to relay data to staff, students, clients, buyers, and suppliers from various locations across the world. In essence, this mode of telecommunication allows a business to effectively carry out its daily function regardless of location. 

Many technologies are available for WAN links. Examples include circuit-switched telephone lines, radio wave transmission, and optical fiber. New developments in technologies have successively increased transmission rates. However, the traditional WAN function was to connect users at the branch or campus to applications hosted on servers in the data center. This doesn't work in a cloud-centric world.

WANs face important operational challenges, including network congestion, packet delay variation, packet loss, and even service outages. Modern applications such as VoIP calling, videoconferencing, streaming media, and virtualized applications and desktops require low latency. Bandwidth requirements are also increasing, especially for applications featuring high-definition video. It can be expensive and difficult to expand WAN capability, with corresponding difficulties related to network management and troubleshooting.

- Today's IT Challenges

Times have changed. That is because WANs designed for a different era are not ready for the unprecedented explosion of WAN traffic that cloud adoption brings. That traffic causes management complexity, application-performance unpredictability, and data vulnerability. Further, opening the enterprise to the Internet and the cloud exposes major threat and compliance issues. It is extremely challenging to protect the critical assets of an enterprise when applications are accessed by a diverse workforce, including employees, partners, contractors, vendors, and guests. Enabling broadband on the WAN makes the security requirements more acute, creating challenges for IT in balancing user experience, security, and complexity. New business models drive the need for a new network model.

- Software Defined Networking (SDN)

Software-defined networking (SDN) is an architecture designed to make a network more flexible and easier to manage. SDN centralizes management by abstracting the control plane from the data forwarding function in the discrete networking devices.

SDN is cloud-based software that allows for management of the network from one central point. The key is virtualization, which makes it so software can run separately from hardware. It would be automatically responsive, and information technology personnel could view all problems from one location and have a much easier time troubleshooting.

An SDN architecture delivers a centralized, programmable network and consists of the following:

• A controller, the core element of an SDN architecture, that enables centralized management and control, automation, and policy enforcement across physical and virtual network environments
• Southbound APIs that relay information between the controller and the individual network devices (such as switches, access points, routers, and firewalls)
• Northbound APIs that relay information between the controller and the applications and policy engines, to which an SDN looks like a single logical network device

- SD-WAN

Software-defined networking in a wide area network (SD-WAN) simplifies the management and operation of a WAN by decoupling the networking hardware from its control mechanism. This concept is similar to how software-defined networking (SDN) implements virtualization technology to improve data center management and operation. 

SD-WAN addresses the current IT challenges. This new approach to network connectivity can lower operational costs and improve resource usage for multisite deployments. Network administrators can use bandwidth more efficiently and can help ensure high levels of performance for critical applications without sacrificing security or data privacy.

A key application of SD-WAN is to allow companies to build higher-performance WANs using lower-cost and commercially available Internet access, enabling businesses to partially or wholly replace more expensive private WAN connection technologies such as MPLS.