Data Link Control
- 2. Data Link Control • Line Discipline • Flow Control • Error Control
- 3. Functions of Data Link Layer Functions of Data Link Layer Figure 10-1
- 4. Figure 10-2
- 5. Figure 10-3
- 11. Figure 10-9 Flow control – set of procedures that tells the sender how much data it can transmit before it must wait for an acknowledgement from the receiver Flow control – set of procedures that tells the sender how much data it can transmit before it must wait for an acknowledgement from the receiver
- 12. Stop and WaitStop and Wait Figure 10-10
- 13. Sliding WindowSliding Window Figure 10-11
- 14. Figure 10-12 Sender Sliding WindowSender Sliding Window
- 15. Figure 10-13 Receiver Sliding WindowReceiver Sliding Window
- 16. Figure 10-14 Sliding Window ExampleSliding Window Example
- 19. Figure 10-15
- 20. Flow Diagram: Normal Operation Time Sender Receiver Time Frame 0 ACK 1 Frame 1 ACK 0 S = 0 S = 1 R = 0 R = 1 R = 0 Deliver Deliver
- 21. Damaged FrameDamaged Frame Figure 10-16
- 22. Flow Diagram: Lost Frame Time Sender Receiver Time Frame 0 ACK 1 Frame 1 ACK 0 S = 0 R = 0 R = 1 R = 0 S = 1 Timeout Frame 1 Deliver Deliver
- 23. Flow Diagram: Lost ACK Time Sender Receiver Time Frame 0 ACK 1 Frame 1 ACK 0 S = 0 R = 0 R = 1 R = 0 Frame 1 S = 1 Timeout ACK 0 S = 1 S = 0 R = 0 Frame 0 expected; discard Deliver Deliver
- 24. Damaged FrameDamaged Frame Figure 10-19
- 25. Lost FrameLost Frame Figure 10-20
- 26. Lost ACKLost ACK Figure 10-21
- 27. Selective RejectSelective Reject Figure 10-22
Editor's Notes
- #6: Two ways
- #7: Dedicated links between two devices
- #8: Initiator – ENQ Responder – ACK or NAK if no response – initiator will assume that the frame was lost - initiator will make 3 attempts before giving up
- #9: All exchanges must be made through the primary PRIMARY – always the initiator
- #10: Selecting – the primary wants to send data to the secondary
- #11: Polling – the primary is asking the secondary if they have something to send NOTE: every secondary device has address
- #12: TWO METHODS RECEIVER – has limited speed at which it can process incoming data - has limited amount of memory in which to store incoming data