Communication Links

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Communication Links

• Communication Link Physical connection or
  Physical Medium
• Types
• Wire Pair or Twisted Pair
• Coaxial Cable
• Fiber Optics
• Bandwidth, Optical Fiber, Light as medium, Low
  noise susceptibility as compared to others
• Micro Wave Transmission
• Satellite Transmission
• Transponder, Geosynchronous sat. orbits _at_ 22,300
  miles

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Microwave and satellite transmission. (a) To relay microwave signals, dish-shaped antennas such as these are often located atop buildings, towers, and mountains. Microwave signals can follow a line-of-sight path only, so stations must relay this signal at regular intervals to avoid interference from the curvature of the earth. (b) In satellite transmission, a satellite acts as a relay station and can transmit data signals from one earth station to another. A signal is sent from an earth station to the relay satellite, which changes the signal frequency before transmitting it to the next earth station. Transponder
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Mixing and Matching
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Protocols

• Set of rules for the exchange of data between a
  terminal and a computer or between two computer
• or precommunication agreement about the form in
  which messages or data is to be sent and receipt
  acknowledged.
• two devices must be able to ask each other
  questions (Are you ready to receive a message?
  Did you get my last message? Is there trouble at
  your end?) and to keep each other informed

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Standard Protocol

• software development can be a nightmare because
  different vendors use different protocols.
  Standards help
• Communications standards exist and are constantly
  evolving and being updated for new communications
  forms
• the most important protocol is the one that makes
  Internet universality possible called
  Transmission Control Protocol/ Internet Protocol
  (TCP/IP)

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Network Topologies

• Physical Layout
• Node (any computer or component)
• Types
• Star
• Hub computer
• Message routed through hub computer
• Ring
• Unidirectional, one at a time
• Bus
• Possible collision, retry if collision

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Kinds of Network

• WAN (wide area network)
• MAN (Metropolitan area network)
• Mainframe to PC connection
• Terminal emulation software
• Micro to mainframe
• Host computer
• File transfer software
• Download, Upload

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Kinds of Network

• LAN (local area network)
• Physical Medium
• Twisted Pair, Co-Axial Cable, Fiber optics etc.
• Wireless (using infra-red or radio waves) Easy
  to install and configure but slow and of short
  range.
• NIC (network interface card)
• The card contains circuitry that handles sending,
  receiving, and error checking of transmitted
  data.

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Networking Components

• Bridge
• Similar networks can be connected by a bridge, a
  hardware/software combination that recognizes the
  messages on a network and passes on those
  addressed to nodes in other networks
• Router
• A router is a special computer that directs
  communications traffic when several networks are
  connected together. If traffic is clogged on one
  path, the router can determine an alternative
  path
• IP Switch
• IP used as Protocol
• routers are being replaced with IP switches,
  which are less expensive and, since no
  translation is needed, faster than routers

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Networking Components

• Gateway
• A gateway is a collection of hardware and
  software resources that lets a node communicate
  with a computer on another dissimilar network
• The main task of Gateway is Protocol conversion

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Types of LAN

• Client Server
• Thin client A computer that has no disk storage
  ability and is used basically to send input to
  the server for processing and then receive the
  output
• Peer to Peer
• All computers in a arrangement have equal status

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LAN Protocols

• Ethernet
• the network protocol that dominates the industry
• uses a high-speed network cable.
• Ethernet uses a bus topology and is inexpensive
  and relatively simple to set up.
• The transmission method used by Ethernet is know
  as carrier sense multiple access with collision
  detection or CSMA/CD
• Token Ring
• Token needed
• Token Ring Uses Ring topology

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Work of Networking

• Office Automation
• E-mail
• Fax (Facsimile)
• Groupware
• Teleconferencing
• Video conferencing
• EDI (electronic Data Interchange)
• Electronic Fund Transfer Instant Banking
• ATM machines
• Telecommuting
• Online services
• Weather, news, online ordering of food, clothing
  etc.