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Communication Systems Engineering Episode 2 Part 4

Tham khảo tài liệu 'communication systems engineering episode 2 part 4', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | Packet Multiple Access II Local Area Networks LANs Eytan Modiano Massachusetts Institute of Technology Department of Aeronautics and Astronautics Eytan Modiano Slide 1 CSMA CD and Ethernet Two way cable CSMA with Collision Detection CD capability - Nodes able to detect collisions - Upon detection of a collision nodes stop transmission Reduce the amount of time wasted on collisions Protocol - All nodes listen to transmissions on the channel - When a node has a packet to send Channel idle Transmit Channel busy wait a random delay binary exponential backoff - If a transmitting node detects a collision it stops transmission Eytan Modiano Slide 2 Waits a random delay and tries again Time to detect collisions WS T WS T prop delay A collision can occur while the signal propagates between the two nodes It would take an additional propagation delay for both users to detect the collision and stop transmitting If T is the maximum propagation delay on the cable then if a collision occurs it can take up to 2t seconds for all nodes involved in the collision to detect and stop transmission Eytan Modiano Slide