sfpsL4CDRActiveFlowSubProtocol 1.3.6.1.4.1.52.4.2.4.2.6.2.4.1.2

If this is a Layer 4 flow, this value identifies the Layer 4 protocol (for IP, this value corresponds to the 'Protocol' field as described in the 'Assigned Numbers' RFC). If this is a Layer 3 flow, this value is zero.