SDNs could be a game changer for next generation provider networks. OpenFlow (OF) - the dominant SDN protocol, is rigid in its South Bound Interface (SBI) - any new protocol field that the hardware must support, must await complete OF standardization. In contrast, OF alternatives such as protocol oblivious forwarding (POF) and ForCES have simpler schemes for insertion of new protocol identifiers. Even with these there is an inherent limitation on network hardware - the tables must support specific table format and configuration at each node as per protocol semantics. We ask the question - can we design an open system - one that is carrier-class, yet able to meet the requirements of any protocol forwarding/action with a minimal set of dataplane function. We propose bitstream, a low-latency, source-routing based scheme that can support new protocols, be compatible with existing protocols and facilitate a minimum semantic set for acting on a packet. A prototype is built to show bitstream working.