5/1/2020 11:43 Rivier College CS575: Advanced LANs

Chapter 6: Logical Link Control

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5/1/2020 11:43 IEEE 802 Protocol Layers Compared to OSI Model 2

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5/1/2020 11:43 Logical Link Control Services

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Unacknowledged connectionless service Connection-mode service Acknowledged connectionless service

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5/1/2020 11:43 Logical Link Control (LLC) Primitives 4

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5/1/2020 11:43 Three LLC Protocols (referred to as types of operation)

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Type 1 operation supports unacknowledged connectionless service Type 2 operation supports connection-mode service Type 3 operation supports acknowledged connectionless service 6

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5/1/2020 11:43 LLC Classes available for a single station 7

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5/1/2020 11:43 LLC Protocol Data Unit Formats 8

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5/1/2020 11:43 LLC Protocol Data Units 9

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5/1/2020 11:43 Examples of High-Level Data Link Control (HDLC) Operation 10

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5/1/2020 11:43 Examples of High-Level Data Link Control (HDLC) Operation 11

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5/1/2020 11:43 Service Primitive Types 12

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5/1/2020 11:43 Time Sequence Diagrams for Service Primitives 13

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5/1/2020 11:43 Flow Control: Model of Frame Transmission 14

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5/1/2020 11:43 Stop-and-Wait Flow Control: Link Utilization 15

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5/1/2020 11:43 Sliding-Window Flow Control Process 16

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5/1/2020 11:43 Example of a Sliding-Window Protocol * Error-detection technique requires an Error-Detecting Code (e.g., CRC) 17

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5/1/2020 11:43 Error Control Mechanisms Two Types of Possible Errors:

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Lost PDU Damaged PDU (some of the bits have been altered during transmission)

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Methods of Error Control:

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Error detection (the receiver detects errors and discards PDUs) Positive acknowledgement is sent confirming error-free PDUs received

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Retransmission after timeout Negative acknowledgement and retransmission

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Automatic Repeat Request (ARQ) turns an unreliable data link into a reliable one.

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5/1/2020 11:43 Stop-and-Wait Automatic Repeat Request (ARQ) 19

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5/1/2020 11:43 Go-Back-N Automatic Repeat Request (ARQ) 20

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