Recent advances in semiconductor technology have resulted in techniques that can build miniaturized radios and sensor-actuators, which can be deployed in the physical world in a large scale. These inexpensive devices can be used to provide coordinated dense sensing, processing, and communicating. Combining these capabilities with robust system software will empower physical sciences with real-time data of high fidelity. To realize this opportunity, computer scientists must address new challenges posed for development of robust system software for the large scale resource constrained wireless networks of embedded devices (sensors). These devices have limited resources in terms of processing, memory, radio bandwidth, and energy. Further, once deployed these devices will necessarily remain untouched and expect to work for an extended period of time. All though Internet is a large scale network, all of the above mentioned constrained do not apply to the nodes in the Internet. Therefore, network services must be designed specifically for the large scale wireless sensor networks. The network services for large scale sensor network must have low time complexity and memory complexity. We provide low complexity reliable and secure data transport for large scale wireless networks of embedded devices. We focus on bulk data transport for two of the most commonly used services, viz. data dissemination and data collection. Our services are better than the state-of-the-art. We address the problem of key maintenance for providing secured communication in the presence of key compromise and denial-of-service attacks. We also investigate the use of testbed to facilitate experimentations for large scale wireless networks.