Network measurement is the basis of scenes including network performance monitoring, traffic management, and fault diagnosis, and in-band network telemetry (INT) has become the focus of network measurement research due to its timeliness, accuracy, and scalability. With the emergence and development of programmable data planes, many practical INT solutions have been proposed thanks to their rich information feedback and flexible function deployment. First, this study analyzes the principles and deployment challenges of typical INT solutions INT and AM-PM. Second, according to the optimization measures and extension of INT, it studies the characteristics of the optimization mechanism from the aspects of the data collection process and multi-tasking, as well as the feasibility of technology extension in terms of wireless networks, optical networks, and hybrid networks. Third, in view of the applications of INT in typical scenes, the characteristics of these INT applications are comparatively investigated from the perspectives of in-network performance sensing, network-level telemetry systems, traffic scheduling, and fault diagnosis. Finally, a research summary of INT is made, and the future research directions are predicted.