networking: computer connections
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Networking: Computer Connections. Chapter 7. Data Communications. Send and receive information over communications lines. Distributed Data Processing. Network. Uses communication equipment to connect two or more computers and their resources - PowerPoint PPT PresentationTRANSCRIPT
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Networking: Computer Connections
Chapter 7
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Data Communications
•Send and receive information over communications lines
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Distributed Data Processing
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Network
• Uses communication equipment to connect two or more computers and their resources
• LAN – shares data and resources among users in close proximity (same floor/building)
• WAN – shares data among users who are geographically distant
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Basic Components
• Sending device
• Communications link
• Receiving device
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Data Transmissionbandwidth
• Digital lines– Sends data as distinct pulses– Need digital line
• Analog lines– Sends a continuous electrical signal in the form of
a wave– Conversion from digital to analog needed– Telephone lines, coaxial cables, microwave
circuits
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Modemlow bandwidth connection
• Modulate– Convert from digital to analog
• Demodulate– Convert from analog to digital
• Speeds up to 56,000 bps (56K)
• (bps: is speed of transferring data
(bits per second)
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Types of Modems
• Direct-connect– External– Internal
• PCMCIA– Personal Computer Memory Card International
Association– Notebook and laptop computers
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Broad bandwidth connections
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ISDNIntegrated Services Digital Network
• Digital transmission• Speeds of 128,000 bps• Connect and talk at same time• Need
– Adapter– Upgraded phone service
• Initial costs high• Ongoing monthly fees may be high• Not available in all areas
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DSLDigital Subscriber Line
• Uses conventional telephone lines• No industry standard
– Cost– Speed
• Phone line shared between computer and voice• Always on• Speed ranges from 1mbps & Up to 10 Mbps• (security problems since its always on)
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Cable Modem
• Coaxial cables
• Does not interfere with cable TV reception
• Up to 10 million bps
• Always on
• Shared capacity
• Security problem
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High Capacity Digital Lines
• T1– 1.54 Mbps
• T3
– 43 Mbps
• Expensive
• High-volume traffic
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Summary of bandwidth connections available for individuals and businesses
• Low speed PPP (modem) : – Modem connections: 28,000k - 56,000K
• High-speed (broad bandwidth) connection to the Internet– ISDN, Cable Modem, DSL, T1, T2, & T3:
• ISDN (Integrated Service Digital Network): Digital transmission over telephone lines. Its speed is up to 128Kbps. Available from Telephone company.
• Cable Modem: connects you PC to a local cable TV line and receives data at 1.5-10 Mbps (Millions bits per second). RCN Cables
• DSL(Digital subscriber line): Digital transmission of data over telephone line. Available from Telephone company.
Speed is about 1- 10 Mbps.• T1: The T-carrier system transmits at 1.43 Mbps.
Used by ISP’s• T2: The T-carrier system transmits at 6.3 Mbps.
Used by ISP’s• T3: Also used by ISP’s. 44 Mbps
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Network Cable
• Twisted pair• Coaxial cable• Fiber optic cable• Wireless
– No cables– Easy to set up and reconfigure– Slower transmission rates– Small distance between nodes– Uses infrared or low-power radio wave transmissions
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Twisted PairWire Pair
• Inexpensive
• Susceptible to electrical interference (noise)
• Telephone systems
• Physical characteristics– Twisted around each other to reduce electrical interference– Plastic sheath
• Shielded twisted pair– Metallic protective sheath– Reduces noise– Increases speed
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Coaxial Cable
• Higher bandwidth
• Less susceptible to noise
• Used in cable TC systems
• Physical characteristics– Center conductor wire– Surrounded by a layer of insulation
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Fiber Optics• Transmits using light
• Higher bandwidth
• Less expensive
• Immune to electrical noise
• More secure – easy to notice an attempt to intercept signal
• Physical characterizes– Glass or plastic fibers– Very thin (thinner than human hair)– Material is light
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Microwave Transmission• Line-of-site
• High speed
• Cost effective
• Easy to implement
• Weather can cause interference
• Physical characteristics– Data signals sent through atmosphere
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Satellite Transmission
• Microwave transmission with a satellite acting as a relay
• Long distance• Components
– Earth stations – send and receive signals– Transponder – satellite
• Receives signal from earth station (uplink)• Amplifies signal• Changes the frequency• Retransmits the data to a receiving earth station
(downlink)
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Satellite Transmission
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CombinationExample – East and West coast:
• Request made– Twisted pair in the phone lines on the East Coast– Microwave and satellite transmission across the
country– Twisted pair in the phone lines on the West coast
• Data transferred– Twisted pair in the phone lines on the West Coast– Microwave and satellite transmission across the
country– Twisted pair in the phone lines on the East coast
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Network TopologyLAN & WAN
• Physical layout– Star– Ring– Bus
• Node – any device connected to the network– Server– Computer– Printer– Other peripheral
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LAN (Local Area Network)
•Connections over short distances through communications media– Same floor or building
Components
• PCs• Network cable
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WANWide Area Network
•Link computers in geographically distant locations