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Data Communications and Networks: A Comprehensive Overview, Slides of Data Communication Systems and Computer Networks
This chapter provides an overview of data communications and networks, discussing various components of a communications model, communications tasks, and simplified data communications models. It also covers the concepts of wide area networks (wans), local area networks (lans), and networking configurations, including wan technologies like circuit switching, packet switching, frame relay, and asynchronous transfer mode (atm), as well as lan technologies such as switched ethernet, atm lan, fibre channel, and wireless networks.
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Chapter 1 Data Communications and Networks Overview
A Communications Model
- Source
- generates data to be transmitted
- Transmitter
- Converts data into transmittable signals
- Transmission System
- Carries data
- Receiver
- Converts received signal into data
- Destination
- Takes incoming data
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
Simplified Communications Model -
Diagram
Simplified Data Communications
Model
Networking
- Point to point communication not usually practical - Devices are too far apart - Large set of devices would need impractical number of connections
- Solution is a communications network
- Wide Area Network (WAN)
- Local Area Network (LAN)
Wide Area Networks
- Large geographical area
- Crossing public rights of way
- Rely in part on common carrier circuits
- Alternative technologies
- Circuit switching
- Packet switching
- Frame relay
- Asynchronous Transfer Mode (ATM)
Circuit Switching
- Dedicated communications path established for the duration of the conversation
- e.g. telephone network
Packet Switching
- Data sent out of sequence
- Small chunks (packets) of data at a time
- Packets passed from node to node between source and destination
- Used for terminal to computer and computer to computer communications
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
Asynchronous Transfer Mode
• ATM
- Evolution of frame relay
- Little overhead for error control
- Fixed packet (called cell) length
- Anything from 10Mbps to Gbps
- Constant data rate using packet switching technique
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
LAN Configurations
- Switched
- Switched Ethernet
- May be single or multiple switches
- ATM LAN
- Fibre Channel
- Switched Ethernet
- Wireless
- Mobility
- Ease of installation
Metropolitan Area Networks
• MAN
- Middle ground between LAN and WAN
- Private or public network
- High speed
- Large area