BUSI 4404 Lecture Notes - Lecture 4: Binary Number, Forward Error Correction, Data Transmission
30 May 2017
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Document Summary
Responsible for moving messages from one device to another. Controls the way messages are sent on media. Organizes physical layer bit streams into coherent messages for the network layer. Major functions: media access control, error control, message delineation. Transmit whenever circuit is available with no centralized control, common in. When devices transmit at the same time, a collision occurs. Devices must be polite and follow these steps: listen for traffic. If another device is transmitting, wait to transmit: otherwise, transmit (keep listening) If another device begins to transmit, stop and wait. Each device must get permission to transmit, similar to raising a hand. Roll-call polling: central device (controller) determines which devices can transmit. Each client is checked periodically to see if it needs to transmit. Hub polling (token passing): one device begins the poll and then passes it to another device until it reaches them all. Types: corrupted data and lost data: caused by problems in transmission (not humans)
