Power grid digital communication networks are needed for the delivery of Phasor Measurement Unit(PMU)  sensor data with real time guarantees to the control centers for timely decisions. Present day network systems are unable to ensure real-time needs of the PMU data as they are not designed to support PMU devices. Hence, the need arises for new communication and control protocols. This paper describes the Cooperative Congestion Control (CCC) framework to ensure real-time guarantees for PMU data and to respond if transient deviations in real-time PMU network traffic occur. The framework utilizes a) NASPI ,  aligned multiple service class queuing architecture; b) Cooperative real-time flow scheduling and bandwidth reassignment; and c) Cooperative coordination and back-pressure approaches among neighboring nodes. It then yields real-time PMU data guarantees during transient traffic pattern changes and/or overload situations. Our experiments confirm that the framework delivers real-time performance very well under different transient stress scenarios.