Abstract of the Master Thesis
The frame relay technology has been proposed to satisfy the requirements of Integrated Services Digital Network (ISDN) concept with a transmission rate of 2 Mbps. Frame relay is a connection oriented packet switching technique and is intended for the interconnection of local area networks. The basic characteristic of frame relay is the division of the data link layer into two sublayers. These are the Data Link Core (DL_CORE) and the Data Link Control (DL_CONTROL) sublayers. The DL_CORE sublayer operates at User-Network Interface (UNI) and reduces the interface functionality as compared to the other packet switching technologies like X.25. The interface functionality includes the detection of transmission and frame errors, framing operations and congestion control. The DL_CONTROL sublayer performs all the usual data link layer functions in an end-to-end manner. In the thesis, a design for the DL_CORE sublayer has been proposed and the corresponding software has been implemented. This is actually the UNI of a communication system based on frame relay. The design for DL_CORE is based on a state transition model. The sublayer software has been developed in C language. The software for frame relay includes both the classical DL_CORE functions as well as the generation of a simulation output. Simulation output consists of the recording of all critical events. The design and implementation are based, but not limited to, the CCITT standards on frame relay.