This volume contains the proceedings of the IFIP WG 6. 1 International Workshop on Testing of Communicating Systems (lWTCS'96), held in Darmstadt, Germany, on September 9 through II, 1996, continuing the IFIP WG 6. 1 series of International Workshops on Protocol Test Systems (IWPTS). In this series of working conferences, held annually since 1988, many valuable contributions have been presented with an emphasis both on the OSI conformance testing methodology and framework as well as the standardization effort on formal methods in conformance testing. While there are stilI open issues and...