OpenFlow per-flow rate limiting

OpenFlow supports per-flow rate-limiters for OpenFlow 1.0 as HPE vendor extensions.

A rate-limiter controls the rate of packets passing through a switch. Per-flow rate-limiters associate an arbitrary number of flows with a rate-limiter. Using OpenFlow with per flow rate-limiters, any number of flows can be flexibly mapped to a rate-limiter, regardless of their source and destination ports. Rate-limiters can be used via the HPE VAN SDN controller, which includes support for HPE QoS extensions. A limiter id (an arbitrary 32-bit number) addresses rate-limiters. Configuration of rate-limiters is done through a simple message from the controller, which can add, modify or remove a rate-limiter. Flows are directed to rate-limiters through an action. Multiple flows can be associated with the same rate-limiter. Statistics can be read from the OpenFlow controller for each rate-limiter.