1. DATA COMMUNICATION
Lecture-39

2. Recap of Lecture 38 Flow Control Stop-and-Wait Sliding Window
Error Control
Stop-and-Wait ARQ

3. Overview of Lecture 39 Error Control Stop-and-Wait ARQ
Sliding Window ARQ
Go-back-n
Selective Reject
Data Link Protocols

4. Error Control

5. Stop-and-Wait ARQ: Damaged Frame

6. Stop-and-Wait ARQ: Lost Frame

7. Stop-and-Wait ARQ: Lost ACK

8. Go-Back-n ARQ: Damaged Frame

9. Go-Back-n ARQ: Lost Frame

10. Go-Back-n ARQ: Lost ACK

11. Selective-Reject ARQ: Damaged Frame

12. Data Link Protocols
Data link protocol is a set of specifications used to implement the data link layer
It contains rules for line discipline, flow control, and error handling

13. Data Link Protocols

14. Asynchronous Protocols
Start and stop bits, variable-length gaps between characters  Inherent slowness
Not complex and inexpensive
Used primarily in modems
Being replaced by higher-speed synchronous mechanisms

15. Asynchronous Protocols

16. XMODEM File transfer protocol between PCs using telephone line
Half-duplex stop-and-wait ARQ protocol
Control frames from the receiver
ACK: Acknowledgement
NAK: Error or start of transmission
CAN: Aborts the transmission

17. XMODEM

18. Summary Error Control Stop-and-Wait ARQ Sliding Window ARQ Go-back-n
Selective Reject
Data Link Protocols

19. Suggested Reading Section 10.3, 11.1,
“Data Communications and Networking” 2nd Edition by Behrouz A. Forouzan