Software-Defined Networking (SDN)

 

Software-defined networking (SDN) is an architecture that aims to make networks agile and flexible. The goal of SDN is to improve network control by enabling enterprises and service providers to respond quickly to changing business requirements.

A typical representation of SDN architecture comprises three layers: the application layer, the control layer and the infrastructure layer.

The application layer, not surprisingly, contains the typical network applications or functions organizations use, which can include intrusion detection systems, load balancing or firewalls. Where a traditional network would use a specialized appliance, such as a firewall or load balancer, a software-defined network replaces the appliance with an application that uses the controller to manage data plane behavior.

SDN architecture separates the network into three distinguishable layers, connected through northbound and southbound APIs. The control layer represents the centralized SDN controller software that acts as the brain of the software-defined network. This controller resides on a server and manages policies and the flow of traffic throughout the network. The infrastructure layer is made up of the physical switches in the network.

With SDN, an administrator can change any network switch's rules when necessary -- prioritizing, deprioritizing or even blocking specific types of packets with a granular level of control and security. This is especially helpful in a cloud computing multi-tenant architecture, because it enables the administrator to manage traffic loads in a flexible and more efficient manner. Essentially, this enables the administrator to use less expensive commodity switches and have more control over network traffic flow than ever before. SDN also virtualizes hardware and services that were previously carried out by dedicated hardware, resulting in the touted benefits of a reduced hardware footprint and lower operational costs.

Security is both a benefit and a concern with SDN technology. The centralized SDN controller presents a single point of failure and, if targeted by an attacker, can prove detrimental to the network. It also provides the following technical and business benefits:

• Directly Programmable: SDN network policy is directly programmable because the control functions are decoupled from forwarding functions, which enables the network to be programmatically configured by proprietary or open source automation tools, including OpenStack, Puppet , Salt, Ansible, and Chef.


• Centralized Management: Network intelligence is logically centralized in an SDN controller software that maintains a global view of the network, which appears to applications and SDN network policy engines as a single, logical switch.


• Reduce capex: Software-Defined Networking potentially limits the need to purchase purpose-built, ASIC-based networking hardware, and instead supports pay-as-you-grow models with its scaling capabilities.


• Reduce opex: SDN enables algorithmic control of the network and network elements (such as hardware or software switches/routers) that are increasingly programmable, making it easier to design, deploy, manage, and scale networks. The ability to automate provisioning and orchestration optimizes service availability and reliability by reducing overall management time and the chance for human error.


• Deliver Agility and Flexibility: SDN can help organizations rapidly deploy new applications, services, and infrastructure to quickly meet changing business goals and objectives.


• Enable Innovation: SDN enables organizations to create new types of applications, services, and business models that can offer new revenue streams and more value from the network.