Data Link Protocols Asynchronous Protocols XMODEM frame ...

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IBM’s Binary SynchronousCommunication (BSC)• Character-oriented protocol• Half-duplex, stop-and-wait ARQ• 2 frame types• Data frame(data transmission)• Control frame(connect/disconnect and flow/error control)A simple BSC data frameSYN = Synchronous idle = 0010110STX = Start of text = 0000010ETX = End of text = 00000117of 538of 53A BSC frame with a headerA multiblock frameHeader Fields:• address (sender/receiver)• #frame identifier (0/1 for stop-and-wait ARQ)ITB = Intermediate text block9of 5310 of 53Multiframe transmissionControl frameETB = End of transmission Block11 of 53Note: Control Frame is used to send command* Establish connection* Maintaining flow & error control* terminating connection12 of 532
Control framesControl frames13 of 5314 of 53Control framesData Transparency• BSC is designed for text message• Now, non-text message (graphics,…)• Problem?• BSC control character problem• Data transparency: should be able tosend any data15 of 5316 of 53Byte stuffingData Link ProtocolsAsynchronousProtocolsSynchronousProtocols• Xmodem• Ymodem• Zmodem• BLAST• KermitCharacter-oriented(Byte-oriented)Bit-orientedDLE = data link escape17 of 53• BSC18 of 533
Page 1: Data Link ProtocolsData Link Protoc
Page 5 and 6: HDLC Configurations:SymmetricalHDLC
Page 7 and 8: HDLC frame: Poll / FinalHDLC Frame:
Page 9: HDLC: U-Frame control fieldHDLC: Po

Data Link Protocols Asynchronous Protocols XMODEM frame ...

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