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Overview of Data Communication and Computer Networks
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When we communicate, we are sharing information.
This sharing can be local or remote. Between individuals, local communication usually occurs face to face, while remote communication takes place over distance.
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The term telecommunication, which includes telephony, telegraphy, and television, means communication at a distance (tele means "far“ in Greek) The effectiveness of a data communications system depends on four fundamental characteristics: delivery, accuracy, timeliness, and jitter.
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Data Communication: Definition
Transfer of data from one device to another via some form of transmission medium.
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Data Communication Hi, how are you? 01010001 01010001 Hi, how are you?
Computer
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Components in Communication
1 Message Hi, how are you? 5 Protocol 2 Sender 3 Receiver 4 Medium
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Data Representation Numbers Text Images
8/16/32 bit integers floating point Text ASCII, Unicode Images Bit patterns, Graphics formats JPG/GIF/etc Audio Samples of continuous signal Video Sequence of bitmap images 150 2 255
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Protocols and Standards
A set of rules governing data communications Syntax: format of data block Semantics: meaning of each section Timing: speed and sequencing Standards De facto (in practice) standards not approved but widely adopted De jure (in law) standards approved by an organization
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Direction of Data Flow Simplex: One direction only data flow Server
Monitor data flow data flow Keyboard
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Direction of Data Flow Half Duplex: Both directions, one at a time
E.g., walkie-talkies data flow at time 1 data flow at time 2
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Direction of Data Flow Full Duplex: Both directions simultaneously
E.g., telephone Can be emulated on a single communication link using various methods data flow data flow
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Types of Connections Point-to-point Multipoint (multidrop)
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Point-To-Point Connection
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Multipoint Connection
Wireless
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Topology Topology: physical or logical arrangement of devices
Point-to-point Mesh Star Bus Ring Hybrid
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Point-to-Point Connection
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Fully Connected Mesh Topology
A D B C
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Fully Connected Mesh Topology
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Fully Connected Mesh Topology
Pros: Dedicated links Robustness Privacy Easy to identify fault Cons: A lot of cabling I/O ports Difficult to move
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Star Topology A D Drop Hub B C Drop
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Star Topology A D Switch B C
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Star Topology A D Hub B C
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Star Topology Pros: Cons: One I/O port per device Little cabling
Easy to install Robustness Easy to identify fault Cons: Single point of failure More cabling still required Hub
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Bus Topology Drop line Tap Terminator
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Bus Topology A B C D
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Bus Topology
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Bus Topology Pros: Cons: Little cabling Easy to install
Difficult to modify Difficult to isolate fault Break in the bus cable stops all transmission
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Ring Topology C D B A
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Ring Topology
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Ring Topology Pros: Cons: Easy to install Easy to identify fault
Delay in large ring Break in the ring stops all transmission
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Hybrid Topologies
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Networks Network: a set of devices connected by media links Laptop
Printer Workstation Laptop Scanner Server
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Network Categories Local Area Network (LAN) Wide Area Network (WAN)
Metropolitan Area Network (MAN)
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Local Area Networks Network in a single office, building, or campus
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Wide Area Networks Network providing long-distance communication over a country, a continent, or the whole world
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Metropolitan Area Networks
Network extended over an entire city Bangkhen Kampangsaen
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Network of Networks Company B Company A Company C Company D
Network Interface Card (NIC) Company A Company C Company D
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Internetworking How to allow devices from different standards to communicate Gateways/routers – devices capable of communicating in several standards These become "network of networks"
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Internetworks Two or more networks connected become an internetwork, or internet Example: The Internet Network1 Network2 Gateway Network3
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The Internet The largest internetwork (network of networks) in the world Devices communicating with TCP/IP protocol suite Stanford U. of Utah UC Santa Barbara UCLA
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Summary Data communication Computer networks
Protocols and standards Computer networks Topologies LAN/MAN/WAN Internetworks (networks of networks)
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