Dell EMC SmartFabric OS10 User Guide Release 10.5.0

OpenFlow use cases

OS10 OpenFlow protocol support allows the flexibility of using vendor-neutral applications and to use applications that you create. For example, the OS10 OpenFlow implementation supports L2 applications similar to the ones found in the following websites:

• https://github.com/osrg/ryu/tree/master/ryu/app (only L2 applications are supported)
• https://github.com/osrg/ryu/tree/master/ryu/app

• Switching loop removal

  Consider the case of a single broadcast domain where switching loops are common. This issue occurs because of redundant paths in an L2 network.

  Switching loops create broadcast storms with broadcasts and multicasts being forwarded out of every switch port. Every switch in the network repeatedly re-broadcasts the messages and floods the entire network.

  To solve broadcast storms in an OpenFlow network, a centralized controller makes all the control plane decisions and manages the switches. The controller has the complete view of the topology. MAC address learning is centralized. OpenFlow identifies the correct path and forwards the packets to the relevant switch thereby avoiding switching loops.

• Reactive flow installation

  Consider the case of dynamic learning of flows for bidirectional traffic. Flows are learnt as and when a packet arrives.

  With dynamic learning in an OpenFlow network, the OpenFlow switch receives a packet that does not match the flow table entries and sends the packet to the SDN controller to process it. The controller identifies the path the packet has to traverse and updates the flow table with a new entry. The controller also decides the caching time of the flow table entries.