The network emulation testbed is a promising research area because it provides a platform to fulfill testing requirements, creating emulated environments for conducting experiments. Through such testbeds, heterogeneous resources can be well controlled as emulated environment, and new ideas can be verified in the environment without interfering the real world. Thus, it can be used to reduce the time of the developers for conducting experiment to explore new inventions. Various kinds of network emulation testbed have been around for years, and it can be expected that more testbeds will emerge. To provide an integrated perspective of network emulation testbed, this paper surveys the issues associated in developing network emulation testbeds, including the state-of-the-art of architecture, the interoperability of orchestrating resources, and the way of managing components. Several wide-area, geographically distributed and large-scale network testbeds have been reviewed and discussed. Finally, critical research findings, open issues, and possible future research directions have also been provided.