6. Noisy Channel – Error free channels Noiseless Channel – Error creating channels PROTOCOLS FOR NOISY CHANNELS FOR NOISELESS CHANNELS SIMPLEST STOP AND WAIT ARQ STOP AND WAIT GO BACK N ARQ SELECTIVE REPEAT ARQ
14. (a) Frame 1 lost Time-out Time A Frame 1 Frame 1 Frame 2 Frame 0 ACK ACK B (b) ACK lost Time-out Time A Frame 0 Frame 1 Frame 1 Frame 2 ACK ACK ACK B Need for Sequence Numbers
21. Advantages of Stop and Wait ARQ over simple Stop and Wait protocol It can be used for noisy channels It has both error and flow control mechanism It has a timer implementation
26. Applications IBM Binary Synchronous Communication Protocol (Bisync): Character-oriented data link control. Xmodem: Modem file transfer protocol. Trivial file transfer protocol (RFC 1350): simple protocol for file transfer over UDP.