The Data Link Layer- part 3

Report
IN THE NAME OF GOD
COMPUTER NETWORKS
CHAPTER 3:
THE DATA LINK LAYER
(PART3)
Dr. Shahriar Bijani
Shahed University
March 2014

References:




A. S. Tanenbaum and D. J. Wetherall, Computer
Networks (5th Edition), Pearson Education, the
book slides, 2011.
Chapter 6, Data Communications and Computer
Networks: A Business User's Approach, 6th
Edition
B. A. Forouzan, Data Communications and
Networking, 5th Edition, Behrouz A. Forouzan,
McGraw Hill, lecture slides, 2012.
Mc Graw Hill, Data Link Layer, 2004.
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DATA LINK PROTOCOLS
 Elementary


Utopian Simplex Protocol
Simplex Stop-and-Wait Protocol


Data Link Protocols
Error-Free Channel
Simplex Stop-and-Wait Protocol

Noisy Channel
 Sliding
Window Protocols
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ELEMENTARY DATA LINK PROTOCOLS
Implementation of the physical, data link, and
network layers.
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ELEMENTARY DATA LINK PROTOCOLS
Some definitions needed in the protocols to follow.
These definitions are located in the file protocol.h.
...
5
ELEMENTARY DATA LINK PROTOCOLS
Some definitions needed in the protocols to follow.
These definitions are located in the file protocol.h.
...
6
ELEMENTARY DATA LINK PROTOCOLS
Some definitions needed in the protocols to follow.
These definitions are located in the file protocol.h.
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UTOPIAN SIMPLEX PROTOCOL (1)
A utopian simplex protocol.
8
...
UTOPIAN SIMPLEX PROTOCOL (2)
A utopian simplex protocol.
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STOP AND WAIT
Receiver
Timeout Timeout
Simplest form of reliability
 Example: Bluetooth
 Problems?

Sender
Utilization
 Can only have one frame in flight
at any time

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SIMPLEX STOP-AND-WAIT PROTOCOL
FOR A NOISY CHANNEL (1)
A simplex stop-and-wait protocol.
11
...
SIMPLEX STOP-AND-WAIT PROTOCOL
FOR A NOISY CHANNEL (2)
A simplex stop-and-wait protocol.
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
ARQ (Automatic Repeat reQuest) or PAR
(Positive Acknowledgement with
Retransmission): Protocols in which the sender
waits for a positive acknowledgement before
advancing to the next data
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SLIDING WINDOW PROTOCOLS
Allow multiple outstanding, un-ACKed frames
 Number of un-ACKed frames is called the window
Window


Sender
Made famous by TCP
Receiver
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SLIDING WINDOW PROTOCOLS (1)
A positive acknowledgement, unidirectional with
retransmission protocol.
...
15
SLIDING WINDOW PROTOCOLS (2)
A positive acknowledgement with retransmission
protocol.
...
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SLIDING WINDOW PROTOCOLS (3)
A positive acknowledgement with retransmission
protocol.
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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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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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ONE-BIT SLIDING WINDOW PROTOCOL (1)
...
A bidirectional 1-bit sliding window protocol.
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ONE-BIT SLIDING WINDOW PROTOCOL (2)
...
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A bidirectional 1-bit sliding window protocol.
ONE-BIT SLIDING WINDOW PROTOCOL (3)
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A bidirectional 1-bit sliding window protocol.
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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PROTOCOL USING GO-BACK-N (1)
Pipelining and error recovery. Effect of an error when
(a) receiver’s window size is 1
Go-back-N
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PROTOCOL USING GO-BACK-N (2)
Pipelining and error recovery. Effect of an error when
(b) receiver’s window size is large.
Selective-repeat
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PROTOCOL USING GO-BACK-N (3)
A sliding window protocol using go-back-n.
...
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PROTOCOL USING GO-BACK-N (4)
A sliding window protocol using go-back-n.
...
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PROTOCOL USING GO-BACK-N (5)
A sliding window protocol using go-back-n.
...
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PROTOCOL USING GO-BACK-N (6)
A sliding window protocol using go-back-n.
...
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PROTOCOL USING GO-BACK-N (7)
A sliding window protocol using go-back-n.
...
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PROTOCOL USING GO-BACK-N (8)
A sliding window protocol using go-back-n.
...
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PROTOCOL USING GO-BACK-N (9)
A sliding window protocol using go-back-n.
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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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PROTOCOL USING GO-BACK-N (11)
Send window for Go-Back-N ARQ
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PROTOCOL USING GO-BACK-N (12)
Receive window for Go-Back-N ARQ
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PROTOCOL USING GO-BACK-N (13)
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A Design of Go-Back-N ARQ
PROTOCOL USING SELECTIVE REPEAT (1)
A sliding window protocol using selective repeat.
...
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PROTOCOL USING SELECTIVE REPEAT (2)
A sliding window protocol using selective repeat.
...
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PROTOCOL USING SELECTIVE REPEAT (3)
A sliding window protocol using selective repeat.
...
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PROTOCOL USING SELECTIVE REPEAT (4)
A sliding window protocol using selective repeat.
...
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PROTOCOL USING SELECTIVE REPEAT (5)
A sliding window protocol using selective repeat.
...
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PROTOCOL USING SELECTIVE REPEAT (6)
A sliding window protocol using selective repeat.
...
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PROTOCOL USING SELECTIVE REPEAT (7)
A sliding window protocol using selective repeat.
...
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PROTOCOL USING SELECTIVE REPEAT (8)
A sliding window protocol using selective repeat.
...
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PROTOCOL USING SELECTIVE REPEAT (9)
A sliding window protocol using selective repeat.
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PROTOCOL USING SELECTIVE REPEAT (10)
Send window for Selective Repeat ARQ (above)
Receive window for Selective Repeat ARQ (bellow)
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PROTOCOL USING SELECTIVE REPEAT (11)
a)
b)
c)
d)
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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EXAMPLE DATA LINK PROTOCOLS
1. Packet
over SONET
2. ADSL (Asymmetric Digital Subscriber Loop)
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