Telecommunications

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Telecommunications Networks.

• Communications Hardware
• Modulation Protocols
• Transmission Media
• Synchronous and Asynchronous
• DSL
• Uses of Telecommunications

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LANs, WANs, MANs, and Intranets

• Networks
• LAN s
• WANs
• MANs
• Intranets

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Background

• Early systems processed in batch
• Centralized system
• routine processing delays
• SO...Data Communication was born

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Data Communication

• Combination of computer and communications
  technologies
• Telephone system first choice

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Networks

• Share hardware, software, and data resources
• LANS
• WANS

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Local Area Networks

• Share hardware, software, and data resources
• Confined to one geographical area
• Hardware Components
• Network Cable
• Cable Interface Unit (Hub)
• Network Interface Card (NIC)
• Node (Addressable)
• Server (Shared file, print, or communications)
• Can be wireless, as well

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Network Architecture

• Client/Server
• Peer-to-Peer
• Internet Peer-to-Peer (P2P)

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Network Architecture

• Client/Server
• Server host
• May be dedicated to particular task (file server,
  print server, etc)
• Client other computers and mobiles devices that
  rely on server for its resources
• Scalable
• Centralized security and updating

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Network Architecture

• Peer-to-Peer
• Simple, inexpensive network
• Each computer has equal responsibilities
• Each computer shares hardware and data
• All computers share any peripheral devices
• Internet Peer-to-Peer (P2P)
• File sharing network
• Each user has access to shared files on other
  users hard disks
• Networking software BitTorrent, Limewire,
  Grokster, Gnutella, Gator, etc

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Network Topology

• Star
• Ring
• Modified Ring
• Bus

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Star Topology

• Requires a host computer
• All messages are routed through the host (switch)
• Very Fast
• If peripheral node fails, system stays up
• If the central computer fails, so does the network

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Ring Topology

• All nodes are attached in a circle
• Actually attached to a hub, and ring is inside
  hub
• Messages travel around the ring (with token)
  until they reach the computer to which they are
  addressed
• If the ring is broken, all devices before the
  failed device are unaffected
• Slower than Star, but more RELIABLE in a sense

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Modified Ring Topology

• All nodes are attached to all other nodes
• Messages travel through any combination until
  they reach the computer to which they are
  addressed
• Fast, Very Reliable, but EXPENIVE

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Bus Topology

• Does not require a central or host computer
• Each node manages part of the network
• Information can be transmitted from one computer
  directly to another without traveling through
  every other node
• Terminators at each end to prevent reflection
• The most popular LAN topology
• But large numbers of users
• greatly decrease performance

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Wide Area Networks

• Spread over a large geographical area
• Metropolitan Area Network
• Transmission Media
• Telephone Lines
• Fiber Optic Cables
• Coaxial Cables
• Microwaves
• Satellites

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DATA COMMUNICATIONS

• Problems
• Drop in intensity

Noise
Solution
Amplification
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Hardware

• Digital Signals
• Analog Signals
• Modulationfrom digital to analog
• Demodulationfrom analog to digital
• Modems

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Network Communications Standards

• Defines guidelines for
• how computers access the medium
• Type(s) of media used
• Speeds used on different types of networks
• Physical cable or wireless technology used
• Standard for how two devices communicate is
  called a PROTOCOL

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Protocol

• Modulation Protocols
• handshaking standards
• standards for establishing maintaining
  communication
• May define data format, coding schemes, error
  handling, and sequencing techniques

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Common Protocols and Network Communication
Standards

• Ethernet no central computer most popular
• Token Ring (one token/network)
• TCP/IP rules for packets
• 802.11 (a-n) rules for wireless communication
• Radio waves
• WiFi any network based on 802.11 standards
• Hot spots
• Bluetooth (protocol) for Bluetooth-enabled
  wireless devices
• Short distances (10 meters)
• Usually only two devices (one mobile)

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WAN Hardware

• Multiplexor
• Controller
• polling
• Contention (ethernet)
• Concentrator
• Front-End Processor

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Hardware

• Modulation Protocols
• Transmission Speed
• bps
• baud rate
• Bandwidth
• voice grade
• broadband

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BANDWIDTH

• HIGHEST LOWEST FREQUENCY
• PHONE LINE 3000 300 2700
• HUMAN VOICE 20,000 20 19980
• UNFORMATTED TEXT PAGE
• 5000 BYTES (40,000 bits)
• TV-QUALITY VIDEO (on computer screen)
• 640x480 resolution 307,200 pixels/ screen
• 8 bits/ pixel (256 colors) 2,457,600
  pixels/frame
• Motion requires 30 frames/second, so
• 73,728,00 bps
• Compression allows video at 1.5 Mbps

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Wired Channels

• Wired Transmission Media
• Twisted-Pair Cable
• 9600 bps
• But CAT6 up to 1Gbps
• Highly susceptible to interference
• Coaxial Cable
• 10-36 Mbps
• Fiber-optic Cable
• 10 Gbps ? ?
• Not susceptible to interference (EMI or RFI)

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Wireless Channels-

• Wireless Transmission Media
• Radio
• Bluetooth - 1-2 Mbps
• 802.11b 11Mbps
• 802.11a 54Mbps
• Terrestrial Microwave
• 100-200Mbps
• Satellite Microwave
• 1 Gbps

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Hardware

• Networking Protocols
• simplex
• half-duplex
• full-duplex
• circuit-switching vs. packet switching

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Hardware

• Channels-Transmission Modes
• Synchronous Transmission
• Asynchronous Transmission

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Hardware

• Bridges
• Gateways
• Routers

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Virtual Network Computing

• Server software
• Viewer software
• TCP/IP connection
• www.realvnc.com

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