1. The Data Link Layer
Chapter 3

2. The Medium Access Control Sublayer
Chapter 4

3. Channel Allocation Problem
Static channel allocation
Assumptions for dynamic

4. Assumptions for Dynamic Channel Allocation
Independent traffic
Single channel
Observable Collisions
Continuous or slotted time
Carrier sense or no carrier sense

5. Multiple Access Protocols
ALOHA
Carrier Sense Multiple Access
Collision-free protocols
Limited-contention protocols
Wireless LAN protocols

6. In pure ALOHA, frames are transmitted at completely arbitrary times
User A B C D E
Collision
Collision
Time
In pure ALOHA, frames are transmitted at completely arbitrary times

7. Vulnerable period for the shaded frame.
ALOHA (2)
Vulnerable period for the shaded frame.

8. Throughput versus offered traffic for ALOHA systems.

9. Persistent and Nonpersistent CSMA
Comparison of the channel utilization versus load for various random access protocols.

10. CSMA with Collision Detection
CSMA/CD can be in one of three states: contention, transmission, or idle.

11. Collision-Free Protocols (1)
The basic bit-map protocol.

12. Collision-Free Protocols (2)
Token
Station
Direction of
transmission
Token ring.

13. The binary countdown protocol. A dash indicates silence.

14. Limited-Contention Protocols
Acquisition probability for a symmetric contention channel.

15. The Adaptive Tree Walk Protocol
The tree for eight stations

16. Wireless LAN Protocols (1)
A wireless LAN. (a) A and C are hidden terminals when transmitting to B.

17. Wireless LAN Protocols (2)
A wireless LAN. (b) B and C are exposed terminals when transmitting to A and D.

18. Wireless LAN Protocols (3)
The MACA protocol. (a) A sending an RTS to B. (b) B responding with a CTS to A.

19. Ethernet Physical layer MAC sublayer protocol Ethernet performance
Switched Ethernet
Fast Ethernet
Gigabit Ethernet
10 Gigabit Ethernet
IEEE 802.2: Logical Link Control
Retrospective on Ethernet

20. Classic Ethernet Physical Layer
Architecture of classic Ethernet

21. MAC Sublayer Protocol (1)
Frame formats. (a) Ethernet (DIX). (b) IEEE

22. MAC Sublayer Protocol (2)
Collision detection can take as long as 2.

23. Efficiency of Ethernet at 10 Mbps with 512-bit slot times.
Ethernet Performance
Efficiency of Ethernet at 10 Mbps with 512-bit slot times.

24. Switched Ethernet (1)
(a) Hub. (b) Switch.

25. Switched Ethernet (2) An Ethernet switch. Switch Hub Switch ports
Twisted pair
An Ethernet switch.

26. The original fast Ethernet cabling.

27. A two-station Ethernet
Gigabit Ethernet (1)
A two-station Ethernet

28. A two-station Ethernet
Gigabit Ethernet (2)
A two-station Ethernet

29. Gigabit Ethernet cabling.

30. Gigabit Ethernet cabling

31. 802.11 architecture and protocol stack
Wireless Lans
architecture and protocol stack
physical layer
MAC sublayer protocol
frame structure
Services

32. 802.11 Architecture and Protocol Stack (1)
To Network
Access Point
Client
architecture – infrastructure mode

33. 802.11 Architecture and Protocol Stack (2)
architecture – ad-hoc mode

34. 802.11 Architecture and Protocol Stack (3)
Part of the protocol stack.

35. The 802.11 MAC Sublayer Protocol (1)
Sending a frame with CSMA/CA.

36. The 802.11 MAC Sublayer Protocol (2)
The hidden terminal problem.

37. The 802.11 MAC Sublayer Protocol (3)
The exposed terminal problem.

38. The 802.11 MAC Sublayer Protocol (4)
The use of virtual channel sensing using CSMA/CA.

39. The 802.11 MAC Sublayer Protocol (5)
Interframe spacing in

40. Format of the 802.11 data frame
Frame Structure
Format of the data frame

41. 802.16 architecture and protocol stack
Broadband Wireless
Comparison of with , 3G
architecture and protocol stack
physical layer
frame structure

42. Comparison of 802.16 with 802.11 and 3G
The architecture

43. 802.16 Architecture and Protocol Stack
The protocol stack

44. Frames structure for OFDMA with time division duplexing.
Physical Layer
Frames structure for OFDMA with time division duplexing.

45. 802.16 MAC Sublayer Protocol Classes of service
Constant bit rate service.
Real-time variable bit rate service.
Non-real-time variable bit rate service.
Best-effort service.

46. (a) A generic frame. (b) A bandwidth request frame.
Frame Structure
(a) A generic frame. (b) A bandwidth request frame.

47. Bluetooth Architecture Applications Protocol stack Radio layer
Link layers
Frame structure

48. Bluetooth Architecture
Two piconets can be connected to form a scatternet

49. Bluetooth Protocol Stack
The Bluetooth protocol architecture.

50. Bluetooth Frame Structure
Typical Bluetooth data frame at (a) basic, and (b) enhanced, data rates.

51. RFID EPC Gen 2 architecture EPC Gen 2 physical layer
EPC Gen 2 tag identification layer
Tag identification message formats

52. EPC Gen 2 Architecture
RFID architecture.

53. Reader and tag backscatter signals.
EPC Gen 2 Physical Layer
Reader and tag backscatter signals.

54. EPC Gen 2 Tag Identification Layer
Example message exchange to identify a tag.

55. Tag Identification Message Formats
Format of the Query message.

56. Data Link Layer Switching
Uses of bridges
Learning bridges
Spanning tree bridges
Repeaters, hubs, bridges, switches, routers, and gateways
Virtual LANs

57. Bridge connecting two multidrop LANs
Learning Bridges (1)
Bridge connecting two multidrop LANs

58. Bridges (and a hub) connecting seven point-to-point stations.
Learning Bridges (2)
Bridges (and a hub) connecting seven point-to-point stations.

59. Protocol processing at a bridge.
Learning Bridges (3)
Protocol processing at a bridge.

60. Spanning Tree Bridges (1)
Bridges with two parallel links

61. Spanning Tree Bridges (2)
A spanning tree connecting five bridges. The dotted lines are links that are not part of the spanning tree.

62. Poem by Radia Perlman (1985) Algorithm for Spanning Tree (1)
I think that I shall never see A graph more lovely than a tree. A tree whose crucial property Is loop-free connectivity. A tree which must be sure to span. So packets can reach every LAN

63. Poem by Radia Perlman (1985) Algorithm for Spanning Tree (2)
. . . First the Root must be selected By ID it is elected. Least cost paths from Root are traced In the tree these paths are placed. A mesh is made by folks like me Then bridges find a spanning tree.

64. Repeaters, Hubs, Bridges, Switches, Routers, and Gateways
(a) Which device is in which layer. (b) Frames, packets, and headers.

65. A building with centralized wiring using hubs and a switch.
Virtual LANs (1)
A building with centralized wiring using hubs and a switch.

66. Two VLANs, gray and white, on a bridged LAN.
Virtual LANs (2)
Two VLANs, gray and white, on a bridged LAN.

67. The IEEE 802.1Q Standard (1)
Bridged LAN that is only partly VLAN-aware. The shaded symbols are VLAN aware. The empty ones are not.

68. The 802.3 (legacy) and 802.1Q Ethernet frame formats.
The IEEE 802.1Q Standard (2)
The (legacy) and 802.1Q Ethernet frame formats.

69. End
Chapter 4

70. Sliding Window Protocols (1)
. . .
A positive acknowledgement with retransmission protocol.
Computer Networks, Fifth Edition by Andrew Tanenbaum and David Wetherall, © Pearson Education-Prentice Hall, 2011

71. Sliding Window Protocols (2)
. . .
A positive acknowledgement with retransmission protocol.
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72. Sliding Window Protocols (3)
A positive acknowledgement with retransmission protocol.
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73. Sliding Window Protocols (4)
A sliding window of size 1, with a 3-bit sequence number. (a) Initially. (b) After the first frame has been sent.
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74. Sliding Window Protocols (5)
A sliding window of size 1, with a 3-bit sequence number
(c) After the first frame has been received. (d) After the first acknowledgement has been received.
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75. One-Bit Sliding Window Protocol (1)
. . .
A 1-bit sliding window protocol.
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76. One-Bit Sliding Window Protocol (2)
. . .
A 1-bit sliding window protocol.
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77. One-Bit Sliding Window Protocol (3)
A 1-bit sliding window protocol.
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78. One-Bit Sliding Window Protocol (4)
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
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79. Protocol Using Go-Back-N (1)
Pipelining and error recovery. Effect of an error when
(a) receiver’s window size is 1
Computer Networks, Fifth Edition by Andrew Tanenbaum and David Wetherall, © Pearson Education-Prentice Hall, 2011

80. Protocol Using Go-Back-N (2)
Pipelining and error recovery. Effect of an error when
(b) receiver’s window size is large.
Computer Networks, Fifth Edition by Andrew Tanenbaum and David Wetherall, © Pearson Education-Prentice Hall, 2011

81. Protocol Using Go-Back-N (3)
. . .
A sliding window protocol using go-back-n.
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82. Protocol Using Go-Back-N (4)
. . .
A sliding window protocol using go-back-n.
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83. Protocol Using Go-Back-N (5)
. . .
A sliding window protocol using go-back-n.
Computer Networks, Fifth Edition by Andrew Tanenbaum and David Wetherall, © Pearson Education-Prentice Hall, 2011

84. Protocol Using Go-Back-N (6)
. . .
A sliding window protocol using go-back-n.
Computer Networks, Fifth Edition by Andrew Tanenbaum and David Wetherall, © Pearson Education-Prentice Hall, 2011

85. Protocol Using Go-Back-N (7)
. . .
A sliding window protocol using go-back-n.
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86. Protocol Using Go-Back-N (8)
. . .
A sliding window protocol using go-back-n.
Computer Networks, Fifth Edition by Andrew Tanenbaum and David Wetherall, © Pearson Education-Prentice Hall, 2011

87. Protocol Using Go-Back-N (9)
A sliding window protocol using go-back-n.
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88. Protocol Using Go-Back-N (10)
Simulation of multiple timers in software. (a) The queued timeouts (b) The situation after the first timeout has expired.
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89. Protocol Using Selective Repeat (1)
. . .
A sliding window protocol using selective repeat.
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90. Protocol Using Selective Repeat (2)
. . .
A sliding window protocol using selective repeat.
Computer Networks, Fifth Edition by Andrew Tanenbaum and David Wetherall, © Pearson Education-Prentice Hall, 2011

91. Protocol Using Selective Repeat (3)
. . .
A sliding window protocol using selective repeat.
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92. Protocol Using Selective Repeat (4)
. . .
A sliding window protocol using selective repeat.
Computer Networks, Fifth Edition by Andrew Tanenbaum and David Wetherall, © Pearson Education-Prentice Hall, 2011

93. Protocol Using Selective Repeat (5)
. . .
A sliding window protocol using selective repeat.
Computer Networks, Fifth Edition by Andrew Tanenbaum and David Wetherall, © Pearson Education-Prentice Hall, 2011

94. Protocol Using Selective Repeat (6)
. . .
A sliding window protocol using selective repeat.
Computer Networks, Fifth Edition by Andrew Tanenbaum and David Wetherall, © Pearson Education-Prentice Hall, 2011

95. Protocol Using Selective Repeat (7)
. . .
A sliding window protocol using selective repeat.
Computer Networks, Fifth Edition by Andrew Tanenbaum and David Wetherall, © Pearson Education-Prentice Hall, 2011

96. Protocol Using Selective Repeat (8)
. . .
A sliding window protocol using selective repeat.
Computer Networks, Fifth Edition by Andrew Tanenbaum and David Wetherall, © Pearson Education-Prentice Hall, 2011

97. Protocol Using Selective Repeat (9)
A sliding window protocol using selective repeat.
Computer Networks, Fifth Edition by Andrew Tanenbaum and David Wetherall, © Pearson Education-Prentice Hall, 2011

98. Protocol Using Selective Repeat (10)
Initial situation with a window of size7
After 7 frames sent and received but not acknowledged.
Initial situation with a window size of 4.
After 4 frames sent and received but not acknowledged.
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99. Example Data Link Protocols
Packet over SONET
ADSL (Asymmetric Digital Subscriber Loop)
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100. Packet over SONET (1)
Packet over SONET. (a) A protocol stack. (b) Frame relationships
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101. Packet over SONET (2) PPP Features Separate packets, error detection
Link Control Protocol
Network Control Protocol
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102. Packet over SONET (3)
The PPP full frame format for unnumbered mode operation
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103. Packet over SONET (4)
State diagram for bringing a PPP link up and down
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104. ADSL (Asymmetric Digital Subscriber Loop) (1)
ADSL protocol stacks.
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105. ADSL (Asymmetric Digital Subscriber Loop) (1)
AAL5 frame carrying PPP data
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106. End
Chapter 3
Computer Networks, Fifth Edition by Andrew Tanenbaum and David Wetherall, © Pearson Education-Prentice Hall, 2011