Transcript COE 342 - 1 Data and Computer Communications

COE 342 - 1
Data and Computer Communications
Data Communications &
Networking Overview
Communication Model
Source System
Destination System
Source
Destination
Transmitter
Transmission System
Reciver
COE 205
Term 042
Dr.Talal AlKharobi
2
Communication Model
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Fundamental purpose of communications system is exchange of
data between two parties
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The key elements of a communication model are
 Source: Generates data to be transmitted
 Transmitter: Converts data into transmittable signals
(modulation, encoding, …)
 Transmission System: Carries data
 Receiver: Converts received signal into data (the opposite of
the “Transmitter” role)
 Destination: Takes incoming data
COE 205
Term 042
Dr.Talal AlKharobi
3
Communications Tasks

Transmission system utilization

Interfacing
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Signal generation

Synchronization

Exchange management

Error detection and correction

Flow control

Addressing

Routing

Recovery

Message formatting

Security

Network management
COE 205
Term 042
Dr.Talal AlKharobi
4
Communications Tasks
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Transmission system utilization
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Making efficient use of transmission facilities
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Multiplexing is used to allocate the total transmission medium among number
of users
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Congestion control is needed to assure that the transmission system is not
overwhelmed

Interfacing: Interfacing here refers to how to interface communicating devices
to the transmission system

Signal generation : Most forms of computer communication depend on the use
of electromagnetic signals propagated over transmission media. Thus, we need to
generate signals from the data to be transmitted.
COE 205
Term 042
Dr.Talal AlKharobi
5
Communications Tasks

Synchronization: The receiver needs to know when the signal start and ends.
Also, it needs to know the duration of each signal

Exchange management: The communicating parties need to agree on a variety
of requirements to communicate usefully. Such conventions include
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Signal timing
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How to start/end conversation
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Simultaneous transmission or taking turns
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Amount of data to be sent at one time
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Data format
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Dealing with errors
COE 205
Term 042
Dr.Talal AlKharobi
6
Communications Tasks
Error detection and correction:
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In all communication system there is a potential for error (signal distortion,
attenuation, interference)
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In most cases, error in transmission is not accepted (tolerated)
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We need to have a technique to detect errors in transmission and even better to
have a technique to correct errors
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Flow control: Flow control is required to assure that the source does not send
information too fast
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Addressing: When more than two devices share transmission facility:
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Each system need to have unique address.

Source need to identify the destination by its address.
COE 205
Term 042
Dr.Talal AlKharobi
7
Communications Tasks
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Routing: the transmission system must assure that the destination system
receive the data

Recovery: Recovery is needed when the information exchange is interrupted or
to restore the system to the point prior to the beginning of the exchange

Message formatting: Communicating parties need to agree on the form of data
to be transmitted such as the binary code for characters

Security:
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Data sender need to assure that only the intended destination receive the
data.

Destination need to be sure that what he recived was sent actually by the
purported sender.

Destination need to be sure that the data has not been altered
COE 205
Term 042
Dr.Talal AlKharobi
8
Communications Tasks

Network management: Network management is needed to
 configure the system
 Monitor the system status
 React to failures and overload
 Plan for future growth
COE 205
Term 042
Dr.Talal AlKharobi
9