COE 341: Data & Computer Communications (T081)Dr. Marwan Abu-Amara
Chapter 1: Data Communications & Networking Overview
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Acknowledgements
Many figures, slides, and course notes were made
available by: Pearson Prentice-Hall
Data & Computer Communications, W. Stallings McGraw-Hill
Data Communications & Networking, B. Forouzan Previous Course Offerings at KFUPM COE by:
Dr. Radwan E. Abdel-Aal Dr. Ashraf Mahmoud Dr. Taha Landolsi
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Course Outline Data Communications & Networking Overview (Ch. 1) Protocol Architecture (Ch. 2) Data Transmission (Ch. 3) Guided and Wireless Transmission (Ch. 4) Signal Encoding Techniques (Ch. 5) Digital Data Communication Techniques (Ch. 6) Data Link Control (Ch. 7) Multiplexing (Ch. 8)
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Agenda Introduction Communications Model
Main blocks and functionality Communication Tasks
Data Communications Data Communication Networking
Wide Area Networks Circuit switching Packet switching Frame Relay ATM
Local Area Networks
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Introduction Fundamental purpose of communications
system is exchange of data between 2 parties 3 general areas:
Data Communications (main concern of COE341) Transmission of signals in reliable & efficient manner Covers signal transmission, transmission media, signal
encoding, interfacing, data link control, multiplexing Networking
Covers technology & architecture of communication networks
Divided into LANs & WANs Protocols
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Simplified Communications Model - Diagram
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A Communications Model Source
Generates data to be transmitted Transmitter
Converts data into transmittable signals (modulation, encoding, …)
Transmission System Carries data
Receiver Converts received signal into data (opposite to “Transmitter”
role) Destination
Takes incoming data
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Communications Tasks
Transmission system utilization Addressing
Interfacing Routing
Signal generation Recovery
Synchronization Message formatting
Exchange management Security
Error detection and correction Network management
Flow control
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Simplified Data Communications Model
May involve buffering and/or encoding of digital data (Ch. 5) Modulated signal, s(t), matched to media (Ch. 3 & 4) Transmission Impairments: noise, distortion, etc. (Section 3.3) Ideally received info, m’, should be identical to original input info, m
(Ch. 7) If not, error correction may help restore m (Ch. 7) Else, retransmission is required (Ch. 7)
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Networking
Point to point communication not usually practical Devices are too far apart Large set of devices would need impractical
number of connections (full connectivity of N nodes is N (N – 1) / 2)
Solution is a communications network Wide Area Network (WAN) Local Area Network (LAN)
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Wide Area Networks
Large geographical area Rely in part on common carrier circuits Alternative technologies
Circuit switching Packet switching Frame relay Asynchronous Transfer Mode (ATM)
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Circuit Switching
Dedicated communications path established for the duration of the conversation
e.g. telephone network
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Packet Switching
Data sent out in sequence of small chunks (packets) of data
Packets passed from node to node between source and destination
Used for terminal to computer and computer to computer communications
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Frame Relay
Packet switching systems have large overheads to compensate for errors
Modern systems are more reliable Errors can be caught in end system Most overhead for error control is stripped out Variable-length packets (called frames)
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Asynchronous Transfer Mode (ATM) Evolution of frame relay Combines circuit switching & packet switching Little overhead for error control Fixed-length packets (called cells) Anything from 10Mbps to Gbps Constant data rate while using packet
switching technique
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Local Area Networks
Smaller scope Building or small campus
Usually owned by same organization as attached devices
Data rates much higher Usually broadcast systems Now some switched systems and ATM are
being introduced
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LAN Configurations
Switched Switched Ethernet
May be single or multiple switches ATM LAN Fibre Channel
Wireless Mobility Ease of installation
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Metropolitan Area Networks (MAN) Middle ground between LAN and WAN Private or public network High speed Large area
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NetworkingConfiguration