1. DATA COMMUNICATION
Lecture-40

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

3. Overview of Lecture 40 Data Link Protocols Asynchronous Protocols

4. Asynchronous Protocols

5. XMODEM

6. Other Asynchronous Protocols
YMODEM
ZMODEM
BLAST
(Blocked Asynchronous Transmission)
KERMIT

7. Synchronous Protocols
Fast transmission for LAN, MAN, and WAN
Synchronous Protocols
Character(Byte)-oriented protocols
Bit-oriented protocols

8. Synchronous Protocols

9. Character-Oriented Protocols
Not as efficient as Bit-Oriented Protocols
Seldom used now
Easy to comprehend and provide the basis to study Bit-Oriented Protocols

10. BSC (Binary Synchronous Communication)
A popular character-oriented data link protocol
Developed by IBM in 1964
Half-duplex transmission with stop-and-wait ARQ
Usable in both point-to-point and multipoint configuration

11. BSC (Binary Synchronous Communication)

12. Data Frames
Simple BSC data frame

13. Data Frames
BSC frame with a header

14. Data Frames A Multiblock Frame
Text in a message is often divided between several blocks
 To increase the likelihood of error detection

15. Data Frames Multiframe Transmission

16. Control Frames Control frames serve three purposes:
Establishing connections
Maintaining flow and error control during data transmission
Terminating connections

17. Control Frames
Contain control characters but no data

19. Summary Data Link Protocols Asynchronous Protocols

20. Suggested Reading Section11.1, 11.2
“Data Communications and Networking” 2nd Edition by Behrouz A. Forouzan