OpenFlow

Improved hardware limitations – OpenFlow

OpenFlow principle

The specific implementation of SDN

The traditional network information transmission (Data Path) decided by hardware router; therefore, causing the hardware-specific information for each transmission path on their own, in the condition of the original path fails, it will cause a lot of repeat transmission, waste system resources; and when companies want to update the transmission, they need IT staffs manually update the software hard body, resulting in rising operational costs. OpenFlow plan to handed over the transmission path to a dedicated controller (OpenFlow controller), depending on the transmission path can be optimized transmission needs to save business costs.

When A, B, D are required to send packets to G, in the original structure, no uniform control, the transmission path from the distribution router, three hardware router would choose the same route, i.e., R3, R3 path causing heavy traffic, and other resources (R1, R2, R4) dummy waste. If R3 path transmission fails, ABD will refer both to the new path R2, R2 during limited load, only completed A packet is sent, B and D are both alternates to R4, R4 same packet is sent only to complete the B, D is Finally, use R1 to complete, F point will return a message to the controller, and the controller is assigned A packet through R1, B by R2, C completed by R4 transmission, to avoid wasting resources which under the original framework packet B and D required to repeated twice more to complete the transfer.

OpenFlow protocol separates the data path and the control path. Data forwarding (data path) functions still reside in the exchanger, but the Control path decision unit is transferred to the OpenFlow Controller. OpenFlow Controller and OpenFlow communication with each other through the OpenFlow protocol, which defines a set of message protocol group, such as data packet is received, the packet forwarding, forwarding the routing table changes, as well as access to state statistics. In addition, OpenFlow controller routing table (Flow table entry) packet processing logic can be established, so that it can carry all types of packets that the action taken (for example: sent to the communications port, modify the fields, or discard). When dealing with an unknown packet, Controller also able to create new logic to respond quickly to such an unknown packet processing in the future.

OpenFlow switching

 

OpenFlow Basics