Networking: Computer Connections

1
Networking Computer Connections

• Chapter 7

2
Data Communications

• Send and receive information over communications
  lines

3
Distributed Data Processing
4
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

5
Basic Components

• Sending device
• Communications link
• Receiving device

6
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

11
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)

12
Cable Modem

• Coaxial cables
• Does not interfere with cable TV reception
• Up to 10 million bps
• Always on
• Shared capacity
• Security problem

13
High Capacity Digital Lines

• T1
• 1.54 Mbps
• T3
• 43 Mbps
• Expensive
• High-volume traffic

14
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 ISPs
• T2 The T-carrier system transmits at 6.3 Mbps.
• Used by ISPs
• T3 Also used by ISPs. 44 Mbps

15
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

17
Coaxial Cable

• Higher bandwidth
• Less susceptible to noise
• Used in cable TC systems
• Physical characteristics
• Center conductor wire
• Surrounded by a layer of insulation

18
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

19
Microwave Transmission

• Line-of-site
• High speed
• Cost effective
• Easy to implement
• Weather can cause interference
• Physical characteristics
• Data signals sent through atmosphere

20
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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Combination

• Example 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)

• Components
• PCs
• Network cable

• Connections over short distances through
  communications media
• Same floor or building

25
WANWide Area Network

• Link computers in geographically distant locations