1. DATA COMMUNICATION
Lecture-42

2. Recap of Lecture 41 Synchronous Protocols Bit-Oriented Protocols HDLC
Link Access Protocols (LAPs)

3. Overview of Lecture 42 Local Area Networks (LANs) Project 802
Protocol Data Unit (PDU)
Ethernet

4. Local Area Networks (LANs)
A Local Area Network (LAN) is a data communication system that allows a number of independent devices to communicate directly with each other in a limited geographical area

5. Local Area Networks (LANs)
Four architectures of LANs
IEEE standards
Ethernet
Token Bus
Token Ring
ANSI standard
FDDI

6. LAN Compared with OSI Model

7. Project 802 A project started by the Computer Society of the IEEE
802.1: Internetworking standard for LANs (Not yet complete)
802.2(LLC): Non-architecture-specific upper sub layer
MAC: A number of modules for different LANs

8. Project 802

9. Protocol Data Unit (PDU)
PDU: The data unit in the LLC level
No flag,no CRC,no station address  Added in the MAC layer

10. Protocol Data Unit (PDU)

11. Control Field in PDU

12. Ethernet
Developed by Xerox, and extended by DEC, Intel and Xerox

13. Access Method: CSMA/CD
Multiple Access: Multiple users access to a single line
Carrier Sense: A device listens to the line before it transmits
Collision Detection: Extremely high voltage indicates a collision

14. Access Method: CSMA/CD

15. 10BASE5: Thick Ethernet
Total length of the bus  2500m  To reduce collisions
RG-8 coaxial cable

16. 10 BASE 5: Thick Ethernet

17. Topology of 10 BASE 5

18. Transceiver Connection in 10 BASE 5
Transceiver connecting mechanism
Tap
Often called a vampire tap

19. Transceiver Connection in 10 BASE 5

20. Summary Local Area Networks (LANs) Project 802
Protocol Data Unit (PDU)
Ethernet

21. Suggested Reading Section12.1, 12.2
“Data Communications and Networking” 2nd Edition by Behrouz A. Forouzan