NUS.SOC.CS2105

1
Application
Transport
you are still here
Network
Link
Physical
2
previously, on CS2105
3
techniques for reliable protocol
4
techniques for reliability

1. checksum
2. timer
3. seq number
4. ack
5. nak

5
R 6000 kbpsL 1500 bytesRTT 300 ms
6
(No Transcript)
7
1. increase range of sequence numbers2.
need to buffer more packets
8
Go-Back-N
9
(No Transcript)
10
(No Transcript)
11
Send 1 Packet
12
Receive ACK 3
13
Receive ACK 6
14
Full Window
15
Empty Window
16

• sender

• call from above
• receive ACK (ok)
• receive ACK (err)
• timeout

17

• call from above

18

• recv ACK (ok)

19

• recv ACK (err)

20

• timeout

21

• receiver

1. recv expected packets
2. recv unexpected or corrupted packets

22

• recv expected

23

• recv others

24
Go-Back-N
25
Mid-Term Test11 March 2006LT33 10am-12noon
26
Continuous Assessment
27
Scopeapplication and transport layer(including
labs)
28
Open Bookone double sided, A4 paper allowed
29
QuestionsMCQs and short questions
30
Selective Repeat
31
(No Transcript)
32

• sender

• receiver

33
recv ACK 6

• receiver

34
sender
recv pkt 8
35
recv ACK 3

• receiver

36

• sender

recv pkt 3
37

• sender

• call from above
• receive ACK (ok)
• receive ACK (err)
• timeout

38

• call from above

39

• recv ACK (ok)

40

• recv ACK (err)

41

• timeout

42

• receiver

1. recv pkts in window
2. recv pkts before window
3. recv other packets

43

• recv pkts in windows

44

• recv pkts before windows

45
Sequence Number and Window Size
46
(No Transcript)
47
techniques for reliability

1. checksum
2. timer
3. seq number
4. ack
5. nak
6. window, pipeline