In this paper the requirement for designing transport layer protocol for wireless sensor network is propose. As the sensor network contains sensor node which has limited power supply in the form of battery, so an important issue is saving energy at the sensor node. So the majority of the functionality is implemented at the base station. Many of the wireless sensor network are heterogeneous data flow support e.g. continuous and event driven flow, so the proposed protocol support multiple applications in the same network. The wireless sensor networks are scalable as the number of sensor node increase rapidly. The proposed protocol offers congestion detection and avoidance by setting congestion notification bit using probabilistic approach.