Networks

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Networks

• Adapting Computers to Telecommunications Media

2
Connecting to a Network

• Modems
• most often used to connect to WANs
• Network Interface Cards (NICs)
• used to connect to LANs

3
Modem

• a device that converts digital signals used in
  computers to analog signals that can be
  transferred over the phone lines
• modulate convert digital signals to analog
• demodulate convert analog signals to digital
• typical speeds - 14.4, 28.8, 33.6, 56 kbps
• faxmodems, internal, external
• modem PC card

4
Wide Area Networks

• transmit information over a large geographic
  region
• public
• private - intranets
• connection is usually through a dial-up lines
• modem, modem software
• service providers
• Commercial Online Services
• ISP - Internet Service Provider
• browser for Internet access
• higher speed connection options
• Integrated Services Digital Network (ISDN)
• DirecPC
• T1, T3 dedicated lines

5
Local Area Networks

• a collection of computers and other devices
  connected with a dedicated line
• usually confined to one geographic location
• used for sharing resources
• data
• hardware
• software
• privately run

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A Network Interface Card...

• Prepare data from the computer for the network
  cable
• Send the data to another computer
• Control the flow of data between the computer and
  the cabling system

Networkinterface card
Coaxial cableBNC connector
RJ-45 jack
Expansion slot
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Network Interface Cards...
are designed to support a particular network
standard and communication protocol...

• Ethernet (CSMA/CD)
• Token Ring (token passing)

...that determines how messages are distributed
to workstations and other network devices.
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Ethernet CSMA/CD Protocol
Every workstation examines the address, but only
the one to which it is addressed reads the
message.
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Ethernet CSMA/CD Protocol
Two messages sent simultaneously

• Collision and Resolution

Each sender waits
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Token-Passing Network Protocol
A signal speeds over the network.
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Communications Protocol Examples for WANs

• WAN protocols
• Transmission Control Protocol/Internet Protocol
  (TCP/IP)
• Systems Network Architecture (SNA)
• Fiber Distributed Data Interface (FDDI)

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Network Software Operating System

• allows users to access files and software from
  the server
• manages the software licenses
• controls network security
• manages the communication between the components
  of the LAN and WAN
• Novell Netware, Windows NT Server

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Network Configurations(Type)

• Hierarchical network
• Client-server networks
• Peer-to-peer network

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Hierarchical Local Network
Connects with other networks, terminals, or
workstations
Terminal
Mainframe printer
Mainframehostcomputer
Hub
Terminal
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Client-Server Networks File Server

• each workstation interacts with the server
• workstations do not directly interact with each
  other.
• processing done at the workstations

Workstation
Workstation
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Client-Server NetworksDatabase Server
establishes an interaction between workstations
and servers that alleviates heavy traffic from
using large database files
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Peer-to-Peer Network
File server

• Some workstations act as both workstations and
  file servers.
• Users can access programs and data files from the
  file server or from other workstation acting as a
  file server.

Workstation and server
Workstation
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Network Topologies(Shape)

• Star
• Bus
• Ring
• Combination topologies

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Network Topologies
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Communication Between Networks

• Repeaters
• Routers
• Bridges
• Gateways