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CSMA/XX Protocols Emmanuel Fleury Distributed System and Semantic Group Aalborg University BRICS Denmark CSMA/XX Protocols p.1/17 CSMA Definition S S S S Medium CSMA = Carrier Sense Multi Access Describe the

slide-1
SLIDE 1

CSMA/XX Protocols

Emmanuel Fleury

Distributed System and Semantic Group Aalborg University – BRICS Denmark

CSMA/XX Protocols – p.1/17

slide-2
SLIDE 2

CSMA Definition

Medium

S

  • S
✁

S

✂

S

✄

CSMA = Carrier Sense Multi Access Describe the hardware model (medium, sources).

CSMA/XX Protocols – p.2/17

slide-3
SLIDE 3

CSMA Definition

Medium

S

  • S
✁

S

✂

S

✄

CSMA = Carrier Sense Multi Access Describe the hardware model (medium, sources). CS (Carrier Sense): Sources can sense the medium without modifying the signal.

CSMA/XX Protocols – p.2/17

slide-4
SLIDE 4

CSMA Definition

Medium

S

  • S
✁

S

✂

S

✄

CSMA = Carrier Sense Multi Access Describe the hardware model (medium, sources). CS (Carrier Sense): Sources can sense the medium without modifying the signal. MA (Multi Access): Several sources can access to the medium in the same time.

CSMA/XX Protocols – p.2/17

slide-5
SLIDE 5

CSMA General Protocol

enum bus = {idle,busy} timer t; message m,m;

CSMA/XX Protocols – p.3/17

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SLIDE 6

CSMA General Protocol

enum bus = {idle,busy} timer t; message m,m; Wait

CSMA/XX Protocols – p.3/17

slide-7
SLIDE 7

CSMA General Protocol

enum bus = {idle,busy} timer t; message m,m; Sense Wait

?m

CSMA/XX Protocols – p.3/17

slide-8
SLIDE 8

CSMA General Protocol

enum bus = {idle,busy} timer t; message m,m; Sense Random Wait Wait

?m bus!=idle, t:=rand() timeout(t)

CSMA/XX Protocols – p.3/17

slide-9
SLIDE 9

CSMA General Protocol

enum bus = {idle,busy} timer t; message m,m; Emit Sense Random Wait Wait

bus==idle ?m bus!=idle, t:=rand() timeout(t)

CSMA/XX Protocols – p.3/17

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SLIDE 10

CSMA General Protocol

enum bus = {idle,busy} timer t; message m,m; Emit Sense Random Wait Wait

!m bus==idle ?m bus!=idle, t:=rand() timeout(t)

CSMA/XX Protocols – p.3/17

slide-11
SLIDE 11

XX (Collision Resolution)

But, this general algorithm doesn’t fit with some hardware

constraints. We have to modify slightly the CSMA protocol for each specific case. For example, the protocol used to resolve collisions (signal collision) is different from one hardware to another.

CSMA/XX Protocols – p.4/17

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SLIDE 12

XX (Collision Resolution)

But, this general algorithm doesn’t fit with some hardware

constraints. We have to modify slightly the CSMA protocol for each specific case. For example, the protocol used to resolve collisions (signal collision) is different from one hardware to another. Several protocols are based on CSMA: CSMA/CD (Collision Detection) CSMA/CA (Collision Avoidance) CSMA/DCR (Deterministic Collision Resolution) . . .

CSMA/XX Protocols – p.4/17

slide-13
SLIDE 13

CSMA/CD History

CSMA/XX Protocols – p.5/17

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SLIDE 14

CSMA/CD History

1973 Ethernet (3 Mbps) (Bob Metcalf at Palo Alto Xerox Research Center),

CSMA/XX Protocols – p.5/17

slide-15
SLIDE 15

CSMA/CD History

1973 Ethernet (3 Mbps) (Bob Metcalf at Palo Alto Xerox Research Center), 1978 Ethernet (10 Mbps) (DEC, Intel, Xerox),

CSMA/XX Protocols – p.5/17

slide-16
SLIDE 16

CSMA/CD History

1973 Ethernet (3 Mbps) (Bob Metcalf at Palo Alto Xerox Research Center), 1978 Ethernet (10 Mbps) (DEC, Intel, Xerox), 1979 3Com Corp. foundation (Bob Metcalf),

CSMA/XX Protocols – p.5/17

slide-17
SLIDE 17

CSMA/CD History

1973 Ethernet (3 Mbps) (Bob Metcalf at Palo Alto Xerox Research Center), 1978 Ethernet (10 Mbps) (DEC, Intel, Xerox), 1979 3Com Corp. foundation (Bob Metcalf), 1985 IEEE 802.3 (Ethernet, 10 Mbps) ISO norm,

CSMA/XX Protocols – p.5/17

slide-18
SLIDE 18

CSMA/CD History

1973 Ethernet (3 Mbps) (Bob Metcalf at Palo Alto Xerox Research Center), 1978 Ethernet (10 Mbps) (DEC, Intel, Xerox), 1979 3Com Corp. foundation (Bob Metcalf), 1985 IEEE 802.3 (Ethernet, 10 Mbps) ISO norm, 1995 IEEE 802.3u (Fast Ethernet, 100 Mbps) ISO norm,

CSMA/XX Protocols – p.5/17

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SLIDE 19

CSMA/CD History

1973 Ethernet (3 Mbps) (Bob Metcalf at Palo Alto Xerox Research Center), 1978 Ethernet (10 Mbps) (DEC, Intel, Xerox), 1979 3Com Corp. foundation (Bob Metcalf), 1985 IEEE 802.3 (Ethernet, 10 Mbps) ISO norm, 1995 IEEE 802.3u (Fast Ethernet, 100 Mbps) ISO norm, 1999 IEEE 802.3z (Gigabit Ethernet, 1 Gbps) ISO norm.

CSMA/XX Protocols – p.5/17

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SLIDE 20

CSMA/CD Hypothesis

Facts

CSMA/XX Protocols – p.6/17

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SLIDE 21

CSMA/CD Hypothesis

Facts

  • 1. Medium = Copper Wire (AUI, BNC, RJ45),

CSMA/XX Protocols – p.6/17

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SLIDE 22

CSMA/CD Hypothesis

Facts

  • 1. Medium = Copper Wire (AUI, BNC, RJ45),
  • 2. Signal = Electrical Signal (Manchester Code),

CSMA/XX Protocols – p.6/17

slide-23
SLIDE 23

CSMA/CD Hypothesis

Facts

  • 1. Medium = Copper Wire (AUI, BNC, RJ45),
  • 2. Signal = Electrical Signal (Manchester Code),
  • 3. Sources = Ethernet Network Cards.

CSMA/XX Protocols – p.6/17

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SLIDE 24

CSMA/CD Hypothesis

Facts

  • 1. Medium = Copper Wire (AUI, BNC, RJ45),
  • 2. Signal = Electrical Signal (Manchester Code),
  • 3. Sources = Ethernet Network Cards.

Synthesis

CSMA/XX Protocols – p.6/17

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SLIDE 25

CSMA/CD Hypothesis

Facts

  • 1. Medium = Copper Wire (AUI, BNC, RJ45),
  • 2. Signal = Electrical Signal (Manchester Code),
  • 3. Sources = Ethernet Network Cards.

Synthesis

  • 1. Diffusion takes time (signal speed about
✂✁ ✄ ✄✆☎

),

CSMA/XX Protocols – p.6/17

slide-26
SLIDE 26

CSMA/CD Hypothesis

Facts

  • 1. Medium = Copper Wire (AUI, BNC, RJ45),
  • 2. Signal = Electrical Signal (Manchester Code),
  • 3. Sources = Ethernet Network Cards.

Synthesis

  • 1. Diffusion takes time (signal speed about
✂✁ ✄ ✄✆☎

),

  • 2. Asynchronous model,

CSMA/XX Protocols – p.6/17

slide-27
SLIDE 27

CSMA/CD Hypothesis

Facts

  • 1. Medium = Copper Wire (AUI, BNC, RJ45),
  • 2. Signal = Electrical Signal (Manchester Code),
  • 3. Sources = Ethernet Network Cards.

Synthesis

  • 1. Diffusion takes time (signal speed about
✂✁ ✄ ✄✆☎

),

  • 2. Asynchronous model,
  • 3. Sources can both sense and emit in the same time,

CSMA/XX Protocols – p.6/17

slide-28
SLIDE 28

CSMA/CD Hypothesis

Facts

  • 1. Medium = Copper Wire (AUI, BNC, RJ45),
  • 2. Signal = Electrical Signal (Manchester Code),
  • 3. Sources = Ethernet Network Cards.

Synthesis

  • 1. Diffusion takes time (signal speed about
✂✁ ✄ ✄✆☎

),

  • 2. Asynchronous model,
  • 3. Sources can both sense and emit in the same time,
  • 4. Collision can be detected,

CSMA/XX Protocols – p.6/17

slide-29
SLIDE 29

CSMA/CD Hypothesis

Facts

  • 1. Medium = Copper Wire (AUI, BNC, RJ45),
  • 2. Signal = Electrical Signal (Manchester Code),
  • 3. Sources = Ethernet Network Cards.

Synthesis

  • 1. Diffusion takes time (signal speed about
✂✁ ✄ ✄✆☎

),

  • 2. Asynchronous model,
  • 3. Sources can both sense and emit in the same time,
  • 4. Collision can be detected,
  • 5. Medium has three modes (idle, busy, jammed).

CSMA/XX Protocols – p.6/17

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SLIDE 30

CSMA/CD WRONG Algorithm

Trying to apply CSMA general algorithm enum bus = {idle,busy,jammed} timer t; message m,m; Emit Sense Random Wait Wait

!m bus==idle ?m bus!=idle, t:=rand() timeout(t)

CSMA/XX Protocols – p.7/17

slide-31
SLIDE 31

What’s WRONG ?

Emit Sense Random Wait Wait

!m bus==idle ?m bus!=idle, t:=rand() timeout(t)

S

  • ,S
✁

,S

✂

,S

✄

Idle

S

  • S
✁

S

✂

S

✄

CSMA/XX Protocols – p.8/17

slide-32
SLIDE 32

What’s WRONG ?

Emit Sense Random Wait Wait

!m bus==idle ?m bus!=idle, t:=rand() timeout(t)

S

✁

,S

✂

S

  • ,S
✄

Idle

S

  • ?

S

✁

S

✂

S

✄

?

CSMA/XX Protocols – p.8/17

slide-33
SLIDE 33

What’s WRONG ?

Emit Sense Random Wait Wait

!m bus==idle ?m bus!=idle, t:=rand() timeout(t)

S

✁

,S

✂

S

✄

S

  • Idle

S

  • S
✁

S

✂

S

✄

?

CSMA/XX Protocols – p.8/17

slide-34
SLIDE 34

What’s WRONG ?

Emit Sense Random Wait Wait

!m bus==idle ?m bus!=idle, t:=rand() timeout(t)

S

✁

,S

✂

S

  • ,S
✄

Idle

S

  • S
✁

S

✂

S

✄

CSMA/XX Protocols – p.8/17

slide-35
SLIDE 35

What’s WRONG ?

Emit Sense Random Wait Wait

!m bus==idle ?m bus!=idle, t:=rand() timeout(t)

S

✁

,S

✂

S

  • ,S
✄

Idle

S

  • S
✁

S

✂

S

✄

Jammed

CSMA/XX Protocols – p.8/17

slide-36
SLIDE 36

CSMA/CD REAL Algorithm

enum bus = {idle,busy,jammed} timer t; message m,m; const float d; // Time to go and back Wait Sense Random Wait Emit

?m bus!=idle, t:=rand() timeout(t) bus==idle !m

CSMA/XX Protocols – p.9/17

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SLIDE 37

CSMA/CD REAL Algorithm

enum bus = {idle,busy,jammed} timer t; message m,m; const float d; // Time to go and back Wait Sense Random Wait

?m bus!=idle, t:=rand() timeout(t)

CSMA/XX Protocols – p.9/17

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SLIDE 38

CSMA/CD REAL Algorithm

enum bus = {idle,busy,jammed} timer t; message m,m; const float d; // Time to go and back Unsafe Emit Wait Sense Random Wait

?m bus==idle, t:=d bus!=idle, t:=rand() timeout(t) (t<d)

  • (bus==jammed),

t:=rand()

CSMA/XX Protocols – p.9/17

slide-39
SLIDE 39

CSMA/CD REAL Algorithm

enum bus = {idle,busy,jammed} timer t; message m,m; const float d; // Time to go and back Safe Emit Unsafe Emit Wait Sense Random Wait

!m timeout(t), bus!=jammed ?m bus==idle, t:=d bus!=idle, t:=rand() timeout(t) (t<d)

  • (bus==jammed),

t:=rand()

CSMA/XX Protocols – p.9/17

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SLIDE 40

CSMA/CD Mini-project

What is expected: Groups of 2-3 people, Report of 4 or 5 pages, Deadline: 12

  • ✁
  • f April.

Questions: Model this protocol for 2 sources in order to check the safety of the emission, Check that if the protocol is in the Safe Emit state, then the message can’t be jammed, Explain the differences between the untimed model and a timed model. Give some examples.

CSMA/XX Protocols – p.10/17

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SLIDE 41

CSMA/CA History

CSMA/XX Protocols – p.11/17

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SLIDE 42

CSMA/CA History

1990 IEEE Working Group on Wireless LAN

CSMA/XX Protocols – p.11/17

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SLIDE 43

CSMA/CA History

1990 IEEE Working Group on Wireless LAN 1997 IEEE 802.11 (1Mbps, 2Mbps) AMD PCnet-Modile (802.11)

CSMA/XX Protocols – p.11/17

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SLIDE 44

CSMA/CA History

1990 IEEE Working Group on Wireless LAN 1997 IEEE 802.11 (1Mbps, 2Mbps) AMD PCnet-Modile (802.11) 1999 IEEE 802.11b (1Mbps, 2Mbps, 5.5Mbps, 11Mbps) Apple Airport (802.11b)

CSMA/XX Protocols – p.11/17

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SLIDE 45

CSMA/CA History

1990 IEEE Working Group on Wireless LAN 1997 IEEE 802.11 (1Mbps, 2Mbps) AMD PCnet-Modile (802.11) 1999 IEEE 802.11b (1Mbps, 2Mbps, 5.5Mbps, 11Mbps) Apple Airport (802.11b) 2000 3Com AirConnect (802.11b) Intel PRO/Wireless 2011 (802.11b)

CSMA/XX Protocols – p.11/17

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SLIDE 46

CSMA/CA History

1990 IEEE Working Group on Wireless LAN 1997 IEEE 802.11 (1Mbps, 2Mbps) AMD PCnet-Modile (802.11) 1999 IEEE 802.11b (1Mbps, 2Mbps, 5.5Mbps, 11Mbps) Apple Airport (802.11b) 2000 3Com AirConnect (802.11b) Intel PRO/Wireless 2011 (802.11b) 2001 IEEE 802.11g, IEEE 802.11h, IEEE 802.11i (1Mbps, 2Mbps, 5.5Mbps, 11Mbps, 54 Mbps)

CSMA/XX Protocols – p.11/17

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SLIDE 47

CSMA/CA Hypothesis

Facts

CSMA/XX Protocols – p.12/17

slide-48
SLIDE 48

CSMA/CA Hypothesis

Facts

  • 1. Medium = Air

CSMA/XX Protocols – p.12/17

slide-49
SLIDE 49

CSMA/CA Hypothesis

Facts

  • 1. Medium = Air
  • 2. Signal = Radio Waves

CSMA/XX Protocols – p.12/17

slide-50
SLIDE 50

CSMA/CA Hypothesis

Facts

  • 1. Medium = Air
  • 2. Signal = Radio Waves
  • 3. Sources = Wireless Network Cards

CSMA/XX Protocols – p.12/17

slide-51
SLIDE 51

CSMA/CA Hypothesis

Facts

  • 1. Medium = Air
  • 2. Signal = Radio Waves
  • 3. Sources = Wireless Network Cards

Synthesis

CSMA/XX Protocols – p.12/17

slide-52
SLIDE 52

CSMA/CA Hypothesis

Facts

  • 1. Medium = Air
  • 2. Signal = Radio Waves
  • 3. Sources = Wireless Network Cards

Synthesis

  • 1. Diffusion takes no time (lightspeed),

CSMA/XX Protocols – p.12/17

slide-53
SLIDE 53

CSMA/CA Hypothesis

Facts

  • 1. Medium = Air
  • 2. Signal = Radio Waves
  • 3. Sources = Wireless Network Cards

Synthesis

  • 1. Diffusion takes no time (lightspeed),
  • 2. Source can either sense or emit,

CSMA/XX Protocols – p.12/17

slide-54
SLIDE 54

CSMA/CA Hypothesis

Facts

  • 1. Medium = Air
  • 2. Signal = Radio Waves
  • 3. Sources = Wireless Network Cards

Synthesis

  • 1. Diffusion takes no time (lightspeed),
  • 2. Source can either sense or emit,
  • 3. Collision cannot be sensed,

CSMA/XX Protocols – p.12/17

slide-55
SLIDE 55

CSMA/CA Hypothesis

Facts

  • 1. Medium = Air
  • 2. Signal = Radio Waves
  • 3. Sources = Wireless Network Cards

Synthesis

  • 1. Diffusion takes no time (lightspeed),
  • 2. Source can either sense or emit,
  • 3. Collision cannot be sensed,
  • 4. Medium has two modes (signal, noise),

CSMA/XX Protocols – p.12/17

slide-56
SLIDE 56

CSMA/CA Hypothesis

Facts

  • 1. Medium = Air
  • 2. Signal = Radio Waves
  • 3. Sources = Wireless Network Cards

Synthesis

  • 1. Diffusion takes no time (lightspeed),
  • 2. Source can either sense or emit,
  • 3. Collision cannot be sensed,
  • 4. Medium has two modes (signal, noise),
  • 5. Each source can reach all the others.

CSMA/XX Protocols – p.12/17

slide-57
SLIDE 57

CSMA/CA Algorithm

enum bus = {signal,noise} timer t; message m,m,SYN,ACK,END; const float d; // Max time to wait for ACK Emit Sense ACK Wait Sense Air Random Wait Stop

!m

  • !END

t<d,?ACK timeout(t) ?m air!=signal, t:=rand() timeout(t), !SYN, t:=d stop(t), ?ACK restart(t), ?END

CSMA/XX Protocols – p.13/17

slide-58
SLIDE 58

CSMA/CA Algorithm – An Example

Emit Sense ACK Wait Sense Air Random Wait Stop S

  • ,S
✁

,S

✂

!m

  • !END

t<d,?ACK timeout(t) ?m air!=signal, t:=rand() timeout(t), !SYN, t:=d stop(t), ?ACK restart(t), ?END

S

✁

S

  • S
✂

Wait Wait Wait

CSMA/XX Protocols – p.14/17

slide-59
SLIDE 59

CSMA/CA Algorithm – An Example

Emit Sense ACK Wait Sense Air Random Wait Stop S

  • S
✁

,S

✂

!m

  • !END

t<d,?ACK timeout(t) ?m air!=signal, t:=rand() timeout(t), !SYN, t:=d stop(t), ?ACK restart(t), ?END

S

✁

S

  • S
✂

Wait m Wait Sense Air

CSMA/XX Protocols – p.14/17

slide-60
SLIDE 60

CSMA/CA Algorithm – An Example

Emit Sense ACK Wait Sense Air Random Wait Stop S

  • S
✁

,S

✂

!m

  • !END

t<d,?ACK timeout(t) ?m air!=signal, t:=rand() timeout(t), !SYN, t:=d stop(t), ?ACK restart(t), ?END

S

✁

S

  • S
✂

Wait Wait Random Wait

CSMA/XX Protocols – p.14/17

slide-61
SLIDE 61

CSMA/CA Algorithm – An Example

Emit Sense ACK Wait Sense Air Random Wait Stop S

✂

S

✁

S

  • !m
  • !END

t<d,?ACK timeout(t) ?m air!=signal, t:=rand() timeout(t), !SYN, t:=d stop(t), ?ACK restart(t), ?END

S

✁

S

  • S
✂

Wait m Sense Air Random Wait

CSMA/XX Protocols – p.14/17

slide-62
SLIDE 62

CSMA/CA Algorithm – An Example

Emit Sense ACK Wait Sense Air Random Wait Stop S

✂

S

  • ,S
✁

!m

  • !END

t<d,?ACK timeout(t) ?m air!=signal, t:=rand() timeout(t), !SYN, t:=d stop(t), ?ACK restart(t), ?END

S

✁

S

  • S
✂

Wait Random Wait Random Wait

CSMA/XX Protocols – p.14/17

slide-63
SLIDE 63

CSMA/CA Algorithm – An Example

Emit Sense ACK Wait Sense Air Random Wait Stop S

✂

S

  • ,S
✁

!m

  • !END

t<d,?ACK timeout(t) ?m air!=signal, t:=rand() timeout(t), !SYN, t:=d stop(t), ?ACK restart(t), ?END

S

✁

S

  • S
✂

Wait SYN SYN Random Wait Random Wait

CSMA/XX Protocols – p.14/17

slide-64
SLIDE 64

CSMA/CA Algorithm – An Example

Emit Sense ACK Wait Sense Air Random Wait Stop S

✂

S

  • S
✁

!m

  • !END

t<d,?ACK timeout(t) ?m air!=signal, t:=rand() timeout(t), !SYN, t:=d stop(t), ?ACK restart(t), ?END

S

✁

S

  • S
✂

Wait Sense ACK Random Wait

CSMA/XX Protocols – p.14/17

slide-65
SLIDE 65

CSMA/CA Algorithm – An Example

Emit Sense ACK Wait Sense Air Random Wait Stop S

✂

S

  • S
✁

!m

  • !END

t<d,?ACK timeout(t) ?m air!=signal, t:=rand() timeout(t), !SYN, t:=d stop(t), ?ACK restart(t), ?END

S

✁

S

  • S
✂

Wait ACK ACK Sense ACK Random Wait

CSMA/XX Protocols – p.14/17

slide-66
SLIDE 66

CSMA/CA Algorithm – An Example

Emit Sense ACK Wait Sense Air Random Wait Stop S

✂

S

  • S
✁

!m

  • !END

t<d,?ACK timeout(t) ?m air!=signal, t:=rand() timeout(t), !SYN, t:=d stop(t), ?ACK restart(t), ?END

S

✁

S

  • S
✂

Wait Message Message Emit Stop

CSMA/XX Protocols – p.14/17

slide-67
SLIDE 67

CSMA/CA Algorithm – An Example

Emit Sense ACK Wait Sense Air Random Wait Stop S

✂

S

  • S
✁

!m

  • !END

t<d,?ACK timeout(t) ?m air!=signal, t:=rand() timeout(t), !SYN, t:=d stop(t), ?ACK restart(t), ?END

S

✁

S

  • S
✂

Wait END END Emit Stop

CSMA/XX Protocols – p.14/17

slide-68
SLIDE 68

CSMA/CA Algorithm – An Example

Emit Sense ACK Wait Sense Air Random Wait Stop S

✂

S

  • S
✁

,

!m

  • !END

t<d,?ACK timeout(t) ?m air!=signal, t:=rand() timeout(t), !SYN, t:=d stop(t), ?ACK restart(t), ?END

S

✁

S

  • S
✂

Wait Wait Random Wait

CSMA/XX Protocols – p.14/17

slide-69
SLIDE 69

Hidden Node Problem

Emit Sense ACK Wait Sense Air Random Wait Stop

!m

  • !END

t<d,?ACK timeout(t) ?m air!=signal, t:=rand() timeout(t), !SYN, t:=d stop(t), ?ACK restart(t), ?END

S

✁

S

  • S
✂

CSMA/XX Protocols – p.15/17

slide-70
SLIDE 70

Hidden Node Problem

Emit Sense ACK Wait Sense Air Random Wait Stop

!m

  • !END

t<d,?ACK timeout(t) ?m air!=signal, t:=rand() timeout(t), !SYN, t:=d stop(t), ?ACK restart(t), ?END

S

✁

S

  • S
✂

S

  • CSMA/XX Protocols – p.15/17
slide-71
SLIDE 71

Hidden Node Problem

Emit Sense ACK Wait Sense Air Random Wait Stop

!m

  • !END

t<d,?ACK timeout(t) ?m air!=signal, t:=rand() timeout(t), !SYN, t:=d stop(t), ?ACK restart(t), ?END

S

✁

S

  • S
✂

S

✁

CSMA/XX Protocols – p.15/17

slide-72
SLIDE 72

Hidden Node Problem

Emit Sense ACK Wait Sense Air Random Wait Stop

!m

  • !END

t<d,?ACK timeout(t) ?m air!=signal, t:=rand() timeout(t), !SYN, t:=d stop(t), ?ACK restart(t), ?END

S

✁

S

  • S
✂

S

✂

CSMA/XX Protocols – p.15/17

slide-73
SLIDE 73

Hidden Node Problem

Emit Sense ACK Wait Sense Air Random Wait Stop S

  • S
✁

,S

✂

!m

  • !END

t<d,?ACK timeout(t) ?m air!=signal, t:=rand() timeout(t), !SYN, t:=d stop(t), ?ACK restart(t), ?END

S

✁

S

  • S
✂

Random Wait Wait Random Wait

CSMA/XX Protocols – p.15/17

slide-74
SLIDE 74

Hidden Node Problem

Emit Sense ACK Wait Sense Air Random Wait Stop S

  • S
✁

,S

✂

!m

  • !END

t<d,?ACK timeout(t) ?m air!=signal, t:=rand() timeout(t), !SYN, t:=d stop(t), ?ACK restart(t), ?END

S

✁

S

  • S
✂

SYN Random Wait Wait Random Wait

CSMA/XX Protocols – p.15/17

slide-75
SLIDE 75

Hidden Node Problem

Emit Sense ACK Wait Sense Air Random Wait Stop S

  • S
✁

S

✂

!m

  • !END

t<d,?ACK timeout(t) ?m air!=signal, t:=rand() timeout(t), !SYN, t:=d stop(t), ?ACK restart(t), ?END

S

✁

S

  • S
✂

Sense ACK Wait Random Wait

CSMA/XX Protocols – p.15/17

slide-76
SLIDE 76

Hidden Node Problem

Emit Sense ACK Wait Sense Air Random Wait Stop S

  • S
✁

S

✂

!m

  • !END

t<d,?ACK timeout(t) ?m air!=signal, t:=rand() timeout(t), !SYN, t:=d stop(t), ?ACK restart(t), ?END

S

✁

S

  • S
✂

ACK ACK Sense ACK Wait Random Wait

CSMA/XX Protocols – p.15/17

slide-77
SLIDE 77

Hidden Node Problem

Emit Sense ACK Wait Sense Air Random Wait Stop S

  • S
✁

S

✂

!m

  • !END

t<d,?ACK timeout(t) ?m air!=signal, t:=rand() timeout(t), !SYN, t:=d stop(t), ?ACK restart(t), ?END

S

✁

S

  • S
✂

Message Emit Wait Stop

CSMA/XX Protocols – p.15/17

slide-78
SLIDE 78

Hidden Node Problem

Emit Sense ACK Wait Sense Air Random Wait Stop S

  • S
✁

S

✂

!m

  • !END

t<d,?ACK timeout(t) ?m air!=signal, t:=rand() timeout(t), !SYN, t:=d stop(t), ?ACK restart(t), ?END

S

✁

S

  • S
✂

END Emit Wait Stop

CSMA/XX Protocols – p.15/17

slide-79
SLIDE 79

Hidden Node Problem

Emit Sense ACK Wait Sense Air Random Wait Stop S

  • ,S
✁

S

✂

!m

  • !END

t<d,?ACK timeout(t) ?m air!=signal, t:=rand() timeout(t), !SYN, t:=d stop(t), ?ACK restart(t), ?END

S

✁

S

  • S
✂

Wait Wait Stop

CSMA/XX Protocols – p.15/17

slide-80
SLIDE 80

CSMA/CA Mini-project

What is expected: Groups of 2-3 people, Report of 4 or 5 pages, Deadline: 12

  • ✁
  • f April.

Questions: Model this protocol for 3 sources in order to check the hidden node problem, Check the existence of the hidden node problem, Explain the differences between the untimed model and a timed model. Give some examples.

CSMA/XX Protocols – p.16/17

slide-81
SLIDE 81

References

802.3:

http://grouper.ieee.org/groups/802/3/

More about Ethernet:

http://www.ethermanage.com/ethernet/ethernet.html

Wireless LAN:

http://grouper.ieee.org/groups/802/11/

More about Wireless protocols:

http://standards.ieee.org/wireless/

Another Wireless Technology: Bluetooth:

http://www.bluetooth.com/

CSMA/XX Protocols – p.17/17