A B C 0 10 20 30 40 50 60 70 80 Ty F0 F1 F2 F3 F4 F5 ACK1 ACK2 ACK3 F0 F0 F1 F2 F3 ACK1 ACK1 ACK2 ACK3 ACK4 dp A B 20 msec dt A B 10 msec dp B C 5 msec dt B C Tg Tg Ty 30 3 x 10 dt 80 dt 1000 R 20 3 R 3000 20 150 Kbps A 0 10 20 30 40 50 60 F0 F1 F2 F3 F4 F5 B C ACK1 ACK2 ACK3 F0 F1 F2 F3 ACK1 ACK2 ACK3 ACK4 dp A B 20 msec dt A B 10 msec dp B C 5 msec dt B C In terms of 3 frames Throughput A B Throughput B C A can transmit three frames to B and then must wait for the acknowledgment of the first frame before transmitting additional frames B can transmit one frame to C at a time dt A B 2 x dp A B 3 x dt A B dp A B R 3000 20 150 Kbps Data Link Control Protocols Error Detection Frame Check Sequence 1 1 0 1 1 1 1 1 1 1 1 0 0 1 1 0 1 0 0 0 0 1 1 0 1 XOR 1 0 0 1 1 1 0 1 1 0 0 0 1 1 0 1 1 0 1 1 1 1 0 1 1 1 0 0 1 1 0 1 1 0 0 0 1 1 0 1 1 0 1 Transmitted pattern 1 0 0 1 1 0 1 0 1 0 1 which is exactly divisible by 1101 1 0 0 1 1 0 1 0 1 0 1 Flip MSB LSB 1 1 0 1 1 0 0 0 1 1 0 1 0 1 0 0 1 1 0 1 1 0 0 Error Detected for 100 sure 1 0 0 1 1 0 1 0 1 0 1 Flip 3 bits 1 1 0 1 1 0 0 0 1 1 0 1 0 0 0 0 1 1 0 1 0 0 0 Error Not Detected Automatic Repeat Query ARQ dp dt 1 sec A Go Back N SWS 3 RWS 1 F0 Selective Reject SWS RWS 4 C B F1 F2 F2 F3 F4 F5 F6 F4 F5 F6 ACK1 F3 F1 ACK1 ACK1 ACK2 ACK3 ACK4 ACK4 ACK4 ACK5 ACK6 ACK7 F0 F1 F2 F3 F4 F5 F6 F4 F1 F2 F3 F4 F5 F6 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 ACK0 ACK1 ACK2 ACK3 ACK5 ACK6 ACK4 F4 A B Throughput 7 x 1000 bits 19 sec 368 4 bps B C Throughput 7 x 1000 bits 22 sec 318 2 bps A C Throughput 7 x 1000 bits 24 sec 292 bps