The X Window System over ISDN-a performance study

Most operational telematic services offer a poor user interface. The X Window System (or X for short) has been found to be a possible replacement for existing telematic protocols, such as Videotex. At present, X is used mainly in local area networks based on TCP/IP and ethernet. In future with telematic services, the X Window System will be used in wide area networks, such as the integrated services digital network (ISDN). Although ISDN is a major improvement over traditional (analogue) telephone systems, compared to local area networks it offers a relatively low data transfer rate. Consequently, performance problems may arise when ISDN is used in combination with X. The paper is based on a study carried out at PTT Research which investigated the above mentioned performance issues. The main objectives of this study were provide insight in traffic generation by X-applications and to produce the basis for a simulation tool for performance evaluation of complex X/ISDN configurations. The first objective was reached by measuring the traffic generated by two characteristic applications; the second by creating accurate, yet simple, model components which can be used to build models of generic complex configurations.