Distributed computer simulation systems use a general-purpose architecture known as HLA (High Level Architecture). HLA aims to provide common architecture for all types of distributed modeling and simulations by providing interoperability and reusability among simulations. A middleware known as RTI (Run Time Infrastructure) provides distributed simulation services under HLA. RTI offers a communication framework which is necessary for federates to interact during simulation process. Many RTI implementations are available commercially and are open source to achieve reusability and interoperability by implementing HLA. However, functionality and performance of RTI is based on its structure. This review presents the performance analysis of multiple RTI implementations, so that the best suitable RTI can be selected for a given simulation scenario and provides the structural comparison of central and service distributed RTI. It also presents the performance analysis of multiple RTI implementations and provides the structural comparison of CeRTI (Central Run Time Infrastructure) and SDRTI (Service Distributed Run Time Infrastructure). Many simulations use HLA, and RTI as basic part of these simulations. This comparative study describes characteristics of different RTIs, their comparisons and implementations that will help the reader to select suitable RTI according to environment and requirements.