Chapter 1. Introduction
1. DATA COMMUNICATIONS
• Telecommunication: communication at a distance
• Data: information presented in whatever form is
agreed upon by the parties creating and using the data
• Data communications: exchange of data between two
users / devices via some form of transmission medium
such as a wire cable
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–
–
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Delivery
Accuracy
Timeliness
Jitter
Five components of data
communication
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•
•
•
•
Message
Sender
Receiver
Medium for transmission
Protocol: set of (explicit and implicit) rules
Data Representation
•
•
•
•
•
Text: ASCII, Unicode, …
Numbers
Images
Audio
Video
Data flow (simplex, half- and full-duplex)
• Communication can be two-way by nature
2. NETWORKS
• Network: a set of devices (often referred to as
users or nodes) connected by communication
links
– A node can be a computer, printer, or any other device
capable of sending and/or receiving data generated by
other nodes on the network
• Performance of network
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–
–
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Throughput
Delay
Reliability (Accuracy and freq. of failures)
Security
Physical Structure of Network
• Types of connections
– Point-to-point, multi-point
• Types of topologies
– Mesh, star, bus, ring
• Covering areas
– LAN, MAN, WAN
Types of connections
Categories of Topology
Ring
Mesh
Star
Bus
Hybrid Topology
• Star + Bus
Covering Area
LAN: Local Area Network
WAN: Wide Area Network
MAN: Metropolitan Area
Network – between LAN
and WAN, e.g., Campus
networks
Inter-network
• A heterogeneous network made of four WANs
and two LANs
3. THE INTERNET
• Impact of “the Internet”
– Revolutionized many aspects of our daily lives:
business, leisure, communications, …
• History
– ARPANET Project (1960s) led by Advanced
Research Project Agency (ARPA) in the Dept. of
Defense (DoD) to establish reliable networks
– Evolves in 1970s and 1980s – TCP/IP
Hierarchical organization of the
Internet
4. PROTOCOLS AND STANDARDS
• Protocols: a set of rules for communications
– Syntax – format
– Semantics – meaning / interpretation
– Timing – when data should be sent, and how fast
they can be sent
• Standards
– Essential in guaranteeing interoperability, and in
creating and maintaining an open and competitive
market
Standards
• Two types
– De facto: not formally approved, but everyone accepts
• MS Word (except Korea), MS Excel
– De jure: formally approved
• WIPI (middleware platform in Korea)
• Standards Organizations
– ISO, ITU-T, CCITT, ANSI, IEEE, EIA, …
• Internet Standards
– Internet Draft, Request for Comment (RFC)
Homework
• Exercise in Chap. 1
– 16
– 17
– 22
– 25