1. The Data Link Layer Chapter 3 10/28/2015www.noteshit.com1

2. Data Link Layer Design Issues Services Provided to the Network Layer Framing Error Control Flow Control 10/28/2015www.noteshit.com2

3. Functions of the Data Link Layer Provide service interface to the network layer Dealing with transmission errors Regulating data flow Slow receivers not swamped by fast senders 10/28/2015www.noteshit.com3

4. Functions of the Data Link Layer (2) Relationship between packets and frames. 10/28/2015www.noteshit.com4

5. Services Provided to Network Layer (a) Virtual communication. (b) Actual communication. 10/28/2015www.noteshit.com5

6. Services Provided to Network Layer (2) Placement of the data link protocol. 10/28/2015www.noteshit.com6

7. Framing A character stream. (a) Without errors. (b) With one error. 10/28/2015www.noteshit.com7

8. Framing (2) (a) A frame delimited by flag bytes. (b) Four examples of byte sequences before and after stuffing. 10/28/2015www.noteshit.com8

9. Framing (3) Bit stuffing (a) The original data. (b) The data as they appear on the line. (c) The data as they are stored in receiver’s memory after destuffing. 10/28/2015www.noteshit.com9

10. Error Detection and Correction Error-Correcting Codes Error-Detecting Codes 10/28/2015www.noteshit.com10

11. Error-Correcting Codes Use of a Hamming code to correct burst errors. 10/28/2015www.noteshit.com11

12. Error-Detecting Codes Calculation of the polynomial code checksum. 10/28/2015www.noteshit.com12

13. Elementary Data Link Protocols An Unrestricted Simplex Protocol A Simplex Stop-and-Wait Protocol A Simplex Protocol for a Noisy Channel 10/28/2015www.noteshit.com13

14. Protocol Definitions Continued  Some definitions needed in the protocols to follow. These are located in the file protocol.h. 10/28/2015www.noteshit.com14

15. Protocol Definitions (ctd.) Some definitions needed in the protocols to follow. These are located in the file protocol.h. 10/28/2015www.noteshit.com15

16. Unrestricted Simplex Protocol 10/28/2015www.noteshit.com16

17. Simplex Stop-and- Wait Protocol 10/28/2015www.noteshit.com17

18. A Simplex Protocol for a Noisy Channel A positive acknowledgement with retransmission protocol. Continued  10/28/2015www.noteshit.com18

19. A Simplex Protocol for a Noisy Channel (ctd.) A positive acknowledgement with retransmission protocol. 10/28/2015www.noteshit.com19

20. Sliding Window Protocols A One-Bit Sliding Window Protocol A Protocol Using Go Back N A Protocol Using Selective Repeat 10/28/2015www.noteshit.com20

21. Sliding Window Protocols (2) A sliding window of size 1, with a 3-bit sequence number. (a) Initially. (b) After the first frame has been sent. (c) After the first frame has been received. (d) After the first acknowledgement has been received. 10/28/2015www.noteshit.com21

22. A One-Bit Sliding Window Protocol Continued  10/28/2015www.noteshit.com22

23. A One-Bit Sliding Window Protocol (ctd.) 10/28/2015www.noteshit.com23

24. A One-Bit Sliding Window Protocol (2) Two scenarios for protocol 4. (a) Normal case. (b) Abnormal case. The notation is (seq, ack, packet number). An asterisk indicates where a network layer accepts a packet. 10/28/2015www.noteshit.com24

25. A Protocol Using Go Back N Pipelining and error recovery. Effect on an error when (a) Receiver’s window size is 1. (b) Receiver’s window size is large. 10/28/2015www.noteshit.com25

26. Sliding Window Protocol Using Go Back N Continued  10/28/2015www.noteshit.com26

27. Sliding Window Protocol Using Go Back N Continued  10/28/2015www.noteshit.com27

28. Sliding Window Protocol Using Go Back N Continued  10/28/2015www.noteshit.com28

29. Sliding Window Protocol Using Go Back N 10/28/2015www.noteshit.com29

30. Sliding Window Protocol Using Go Back N (2) Simulation of multiple timers in software. 10/28/2015www.noteshit.com30

31. A Sliding Window Protocol Using Selective Repeat Continued  10/28/2015www.noteshit.com31

32. Continued  A Sliding Window Protocol Using Selective Repeat (2) 10/28/2015www.noteshit.com32

33. A Sliding Window Protocol Using Selective Repeat (3) Continued  10/28/2015www.noteshit.com33

34. A Sliding Window Protocol Using Selective Repeat (4) 10/28/2015www.noteshit.com34

35. A Sliding Window Protocol Using Selective Repeat (5) (a) Initial situation with a window size seven. (b) After seven frames sent and received, but not acknowledged. (c) Initial situation with a window size of four. (d) After four frames sent and received, but not acknowledged. 10/28/2015www.noteshit.com35

36. Protocol Verification Finite State Machined Models Petri Net Models 10/28/2015www.noteshit.com36

37. Finite State Machined Models (a) State diagram for protocol 3. (b) Transmissions. 10/28/2015www.noteshit.com37

38. Petri Net Models A Petri net with two places and two transitions. 10/28/2015www.noteshit.com38

39. Petri Net Models (2) A Petri net model for protocol 3. 10/28/2015www.noteshit.com39

40. Example Data Link Protocols HDLC – High-Level Data Link Control The Data Link Layer in the Internet 10/28/2015www.noteshit.com40

41. High-Level Data Link Control Frame format for bit-oriented protocols. 10/28/2015www.noteshit.com41

42. High-Level Data Link Control (2) Control field of (a) An information frame. (b) A supervisory frame. (c) An unnumbered frame. 10/28/2015www.noteshit.com42

43. The Data Link Layer in the Internet A home personal computer acting as an internet host. 10/28/2015www.noteshit.com43

44. PPP – Point to Point Protocol The PPP full frame format for unnumbered mode operation. 10/28/2015www.noteshit.com44

45. PPP – Point to Point Protocol (2) A simplified phase diagram for bring a line up and down. 10/28/2015www.noteshit.com45

46. PPP – Point to Point Protocol (3) The LCP frame types. 10/28/2015www.noteshit.com46