The field of teleoperation coupled with force-feedback will undergo a paradigm shift in the forthcoming years with the advent of Tactile Internet (TI). Through TI, humankind will enjoy the ability to control and manipulate remote environments in real time by creating a perception of physical collocation for the human operator. While research and development in TI have seen a surge in the past few years, the overall progress is constrained by two major barriers. First, lack of a TI testbed has made it difficult to establish a performance benchmark. Second, asynchronous efforts led by sub-groups belonging to different research disciplines have severely impeded the overall progress of TI. In this work, we take the first step toward addressing these open issues by developing a common testbed for TI applications -- Tactile Internet eXtensible Testbed (TIXT). We begin by presenting a classification of the diverse range of TI applications. This helps in making TIXT generic, modular, and extensible. We then present the design principles of TIXT and shed light on its implementation guidelines. Finally, we present the proof of concept of TIXT through demonstration of two realistic use cases of TI.