OpenFlow operations with Ryu

To begin with, let's look at two basic components of Ryu code that we have seen in the switch application:

• ryu.base.app_manager: The component that centrally manages Ryu applications. ryu.base.app_manager.RyuApp is the base class that all Ryu applications inherit. It provides contexts to Ryu applications and routes messages among Ryu applications (contexts are ordinary Python objects shared among Ryu applications). It also contains methods such as send_event or send_event_to_observers to raise OpenFlow events.
• ryu.controller: The ryu.controller.controller handles connections from switches and routes events to appropriate entities:
  • ryu.controller.ofp_event: This is the OpenFlow event definition.
  • ryu.controller.ofp_handler: This is the handler of an OpenFlow event. A Ryu application registers itself to listen for specific events using ryu.controller.handler.set_ev_cls decorator. We have seen the decorator set_ev_cls as well as CONFIG_DISPATCHER and MAIN_DISPATCHER...