Learning Objectives

After successfully completing this section, you should be able to

  1. describe some of the protocols commonly used for the link layer.
  2. explain in detail some important LAN technologies.
  3. run the CSMA/CD protocol step-by-step to solve certain network problems.

Learning Tasks

Required:

  1. Watch the slideshow for this section.
  2. Study the following sections in the textbook:

6.3 Multiple Access Links and Protocols
6.4 Switched Local Area Networks

Terms and Topics

Section 3 – Link-Layer Protocols and Local Area Networks

Multiple access links
Multiple access protocols
Point-to-point link
Broadcast link
Multiple access problem
Frame collision
Random access protocols
Characteristics of a multiple access protocol for a broadcast channel
Time frames
Time slots
Code division multiple access (CDMA) protocol
Slotted ALOHA
ALOHA protocol
Carrier sensing
Carrier Sense Multiple Access (CSMA)
Collision detection
Important rules for polite human conversation
Carrier Sense Multiple Access with collision detection (CSMA/CD)
Channel propagation delay
Binary exponential backoff
CSMA/CD efficiency
Taking-turn protocols
Polling protocol
Polls
Token-passing protocol
Token

DOCSIS: link-layer protocol for cable access
Channel partitioning protocols
Switched local area networks
Link-layer addressing
LAN address
Physical address
MAC addresses
Address resolution protocol (ARP)
MAC broadcast address
ARP table
ARP packet
Ethernet
Ethernet frame structure
Technologies for Ethernet
Repeater, hub, switch
Gigabit Ethernet
Buffered distributors
Link-layer switches
Forwarding and filtering at switches
Switch table
Self-learning of switches
Properties of link-layer switches
Differences between switches and routers
Virtual local area networks (VLANs)
VLAN trunking
VLAN tag 

Leading Questions

  1. What is a point-to-point link?
  2. What is a multicast link?
  3. What is the multiple-access problem? How is it solved?
  4. What are channel partitioning protocols? How do they work?
  5. What are random access protocols? How do they work?
  6. What are taking-turns protocols? How do they work?
  7. What is TDM? What is FDM? How do they work?
  8. What is code division multiple access (CDMA)? How does it work?
  9. What is the chipping rate?
  10. What are the ALOHA protocols?
  11. What is the slotted ALOHA protocol?
  12. What are the carrier sense multiple access (CSMA) protocols?
  13. How does the CSMA/CD protocol work?
  14. What are two desirable properties of a multiple access protocol?
  15. What is a LAN address?
  16. Why does a node in a network have a LAN address in addition to a network-layer address?
  17. What is the broadcast address for a LAN?
  18. What is the address resolution protocol (ARP)? Why is it necessary?
  19. How does ARP help send a datagram to a node outside the LAN?
  20. What are the main reasons for the success of Ethernet?
  21. What is the structure of Ethernet frames?
  22. Why is Ethernet said to provide unreliable connectionless services?
  23. What band is used for data transmission in Ethernet?
  24. Why is Manchester encoding used in Ethernet?
  25. What multicast access protocol is used in Ethernet?
  26. Why is a jam signal used in Ethernet?
  27. How is the efficiency of Ethernet defined?
  28. What is a repeater in LANs?
  29. What is 10BASE2 Ethernet?
  30. What physical medium is used to network computers in a 10BASE2 Ethernet?
  31. What are the main topologies for LAN implementation?
  32. What are the important devices used to build 10BASE-T or 100BASE-T Ethernet?
  33. What is Gigabit Ethernet?
  34. What are hubs?
  35. What are bridges?
  36. What are switches?
  37. What are the differences between a hub and a bridge?
  38. What are the differences between a bridge and a switch?
  39. What is a backbone hub?
  40. What is a multi-tier hub design? What is a LAN segment?
  41. Why is it said that all the LAN segments are in the same collision domain?
  42. What are the limitations of using a backbone hub as an interconnection device?
  43. What abilities does a bridge have?
  44. How is the self-learning capability accomplished in bridges?
  45. Why are bridges described as transparent?
  46. What are the advantages of pure hierarchical design for interconnected LAN segments?
  47. Why are multiple paths between LAN segments necessary? What problems are caused by using multiple paths? How is this problem solved by using bridges?
  48. What is the spanning tree protocol?
  49. What are the differences between bridges and routers?
  50. What are the pros and cons of routers?
  51. Which IEEE standard is used for Ethernet?
  52. What advantages does a switch have?
  53. What is cut-through switching?
  54. What is the PPP protocol and where is it commonly used?
  55. What are the original requirements for the design of PPP?
  56. What fields are contained in a PPP frame?
  57. What is byte stuffing? How is it used in PPP design?