Several transport protocols have been proposed for use in the Internet. The specifications of these protocols are based on the assumption that a general purpose transport protocol can be designed to be used by a variety of applications, including time-constrained applications. A widespread consensus among the researchers is that a general purpose transport protocol is not optimized for any applications, and thus cannot deliver the high performance required by real-time applications such as voice, motion and still video, and large file transfer. The purpose of the proposed paper is to investigate the validity of the above claim based on the gathering of empirical data. A generic "protocol benchmark" will be used to assess the real-time performance of a set of known transport protocols, and analyze their suitability to handle the requirements of real-time applications.