Abstractions for Software-Defined Networks

Software-Defined-Network (SDN) is a new network architecture that decouples the software that controls a network from the devices that implement it. By providing global visibility into network state, SDN can dramatically simplify the way that many network algorithms are expressed. SDN also makes it possible to evolve the functionality of a network without having to change the underlying hardware. SDN is enabling the development of new network programming models, systems abstractions, and verification tools. SDN controllers are built using relatively small collections of tightly-coupled servers, which makes them amenable to distributed algorithms that maintain consistent versions of network-wide structures such as topology, traffic statistics, and others. The OpenFlow specification defines a standard collection of features switches must provide, as well as an interface controllers can use to communicate with switches. Consistent update abstractions allow a controller to update the forwarding state of the entire network while ensuring a packet will never traverse a path that is in transition between two state. By standardizing the interfaces for controlling networks, SDN makes it feasible to build tools for verifying configurations and controllers against precise formal models.