Software Defined Networking (SDN) involves an application interacting with a network (composed of domain-specifc devices) for the purpose of simplifying operations or enabling a service. A controller is positioned between the application and network and interacts with network elements (e.g. switches) in the southbound direction using a variety of different protocols. In the northbound direction it presents an abstraction of the network using in practice common REST APIs. The controller vehicle for this applicatin is ODL. This innovation supports applications for managing openflow networks called Openflow Manager (OFM).
Figure 1 show the OFM architecture
From the bottom-up we have a network of openflow switches employing a "Match/Action" forwarding paradigm to execute flow switching operations through the network. Openflow switches support an openflow agent and use the running MPLS for label switching packets across the network, and either OSPF or ISIS to maintain and distribute the topology (link-state) database amongst all routers in the network. One of the routers is a BGP-LS and it transports a copy of the topology database to the ODL controller. The routers will also run a PCEP (stands for path computation element protocol) used by the ODL controller to instruct a source router to setup an MPLS traffic engineered path to a destination router. This is very network- and protocol-specific details, which frankly the end-user may not know or care about. This is where OpenDaylight and applications come into play.
Figure 2 shows the initial display once the OF inventory is collected and rendered. To support topological context for all functions, each panel described below will include this topology/inventory display.
The basic sub functions of OFM as arranged across the top consist of:
A key objective of SDN in general and enabled in open source by ODL is network abstraction thus simplify network operations. Instead of cubersome per-device configuration and managment, we provide a web browser user interface that operators use to manage openflow networks and deivces. OFM is that application.