The sampling parameter in openvswitch to enable IPFIX what it refers to? For example, a value of 1 means what? Furthermore, as the difference there is per-bridge sampling and per-flow sampling?
Almost certainly 1 out of x packets. This is a common technique to reduce overhead for flow processing. A value of 1 means no sampling. If you use a higher value you need to make sure your collection / analysis tools are similarly configured to allow for proper interpolation.