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Prince Mohammed bin Fahd University COEN 4331 Network Theory Sec: 201 Name: Zainab Al-Mabuk ID: 200800942 10-2-2013 Assignment: WAN Technologies. A WAN is a data communications network that covers a relatively broad geographic area and that often uses transmission facilities provided by common carriers, such as telephone companies. WAN technologies generally function at the lower three layers of the OSI reference model: the physical layer, the data link layer, and the network layer. It has different technologies such as: Circuit switching: • Seeking out and establishing a physical copper path from end-to-end [historic definition • Circuit switching implies the need to first set up a dedicated, end-to-end path for the connection before the information transfer takes place. • Once the connection is made the only delay is propagation time. Packet switching: • A store-and-forward network where the block of transfer is a complete packet. A packet is a variable length block of data with a tight upper bound. Using packets improves mean message delay. A setup stage is used to determine the end-to-end path before a connection is established. Frame relay: Frame relay is a telecommunication service designed for cost-efficient data transmission for intermittent traffic between local area networks LANs and between end-points in a wide area network WAN Frame relay puts data in a variable-size unit called a frame and leaves any necessary error correction (retransmission of data) up to the end-points, which speeds up overall data transmission. ATM ATM (asynchronous transfer mode) is a dedicated-connection switching technology that organizes digital data into 53-byte cell units and transmits them over a physical medium using digital signal technology. Individually, a cell is processed asynchronously relative to other related cells and is queued before being multiplexed over the transmission path.