#### Transcript ch11Review

```Assume that a file is transferred from a node A to a node B. The
file has been fragmented in 5 frames. Frame 0 is corrupted, the
ACK of frame 1 is corrupted, ACK of frame 4 arrived after the
time of frame 4 expired. Show the flow of frames exchanged
between the two nodes, and the status of the windows after the
transmission/reception of each information/control frame, if the
field of sequence number is three-bit-length, and the sender and
receiver are using the maximum possible window size, for the
following data link control techniques:
•
•
•
•
•
Simplest
Stop-And-Wait
Stop-and-wait ARQ
Go-back-N ARQ
Selective- Repeat ARQ
Simplest (ideal
channel,
no
error)
A
B
f0
f1
f2
f3
f4
Stop and Wait in ideal channel (no error)
A
B
f0
ACK 1
f1
ACK 0
f1
ACK 0
f0
ACK 1
Stop and Wait ARQ
A
B
f0
Time out
f0
ACK 1
accepted
f1
ACK 0
accepted
f1
ACK 0
f0
ACK 1
accepted
f1
Time out
f1
ACK 0
accepted
Go-Back-N ARQ
0 1 2 3 4 5 6 7 0
A
Time out
Time out
0 1 2 3 4 5 6 7 0
B
f0
f1
f2
f1 f0
ACK 1
f2
ACK 2
f2
f3
0 1 2 3 4 5 6 7 0 …
0 1 2 3 4 5 6 7 8
0 1 2 3 4 5 6 7 8
f1
ACK 4
0 1 2 3 4 5 6 7 8
f4
Time out
0 1 2 3 4 5 6 7 0 …
ACK 5
f4
ACK 5
0 1 2 3 4 5 6 7 8
Duplex Communication
with Stop-and-Wait ARQ
Assume that computer A and computer B communicate with
each other. Each has 3 frames to send to the other. The three
data frames sent by A are denoted as A1, A2, A3 and the frames
from B are B1, B2, B3. They use duplex Stop-and-Wait ARQ for
the communication, i.e., each data frame has a sequence # field
and an Ack # field.
Suppose each data frame needs 1 ms to transmit and each
ack-only frame needs no time to transmit. The time-out value is
set to be 5ms. The round trip time is always 2 ms. Use “A1, (0,1)”
denote a frame with data A1 and sequence 0, ack 1.
Ideal channel without any error/lost or congestion
A1
A2
A3
A
B
B1
B2
B3
Algorithm 11.5 Sender-site algorithm for Stop-and-Wait ARQ
(continued)
11.8
Algorithm 11.5 Sender-site algorithm for Stop-and-Wait ARQ
11.9
(continued)
Algorithm 11.6 Receiver-site algorithm for Stop-and-Wait ARQ Protocol
11.10
Rn is the sequence number of
the next packet expected
Stop-and-Wait ARQ Example
Assume that computer A sends 3 frames to computer B. The
three data frames sent by A are denoted as A1, A2, A3. Suppose
each data frame needs 1 ms to transmit and each ack frame
needs no time to transmit. The time-out value is set to be 4ms.
The round trip time is always 2 ms. Use “A1, 0” denote a frame
with data A1 and sequence 0. Use “Ack 1” denote an ack frame
with ack number 1.
Case 1: Ideal channel without any error/lost or
congestion
A1
A2
A3
A
B
Case 2: second frame from A to B is lost
A1
A2
A3
A
B
Case 3: second frame from A to B uses 3 ms
A1
A2
A3
A
B
Case 4: second ack frame from B to A uses 3ms
A1
A2
A3
A
B
```