Telecommunications and Networks

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• Telecommunications and Networks
• Why Networks?
• Communication
• Coordination
• Collaboration
• Information and resource sharing.

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• Networks reduce cost of doing business
• Networks improve business efficiency
• Networks open new business opportunities.
• ..
• Network is the Business!!!

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Netwo

• Networks will dramatically change the way we
  Work, Live, Learn and Play
• Bold Prediction
• A business that does not leverage networks
  (Internet) within the next year may not exist in
  five years.

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• Host Independent computer system connected to
  the network.
• Node Component connected to the network

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• Nodes Hubs, Hosts, Router, gateways, bridge,
  switch ..
• Example of a network
• ARPANET --gt Internet.

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• Classification of Networks
• By Geography (how big?)
• By type of Wiring, connections
• By type of use
• By type of technology
• By type of protocol
• .

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• Types of Networks
• LAN (Local Area Networks )
• WAN (Wide Area Networks)
• MAN (Metropolit Area Networks)
• Campus Networks

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• What is a LAN?

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• Network Topologies
• Physical Topology Physical configuration of
  nodes.
• Bus, Ring, Star, Hybrid, mesh
• Logical Topology Electrical circuit of the
  network. How data is sent.

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• Bus Topology Nodes connected to common shared
  cable (backbone).
• Broadcast in both directions.Terminator

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Bus topology
Star topology
Hub
Ring topology
GOLDMAN DATACOMM
FIG. 05-07
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• Ring Connected in a circle. Data passes in one
  direction only.
• Token passing access method.
• Not robust.

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• Star Topology All Devices connected to central
  hub.
• Robust. Complicated wiring

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• Mesh Topology Every node is connected to every
  other node.
• Extremely Fault-tolerant. One or more failures
  does not disrupt the network.
• Used in WANs, not LANs.

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• Access Methods
• Rules governing how nodes share the transmission
  medium.
• Carrier Detection in Ethernet
• Token Passing in token ring
• Demand priority in 100VG-anyLAN

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• LAN Technologies
• EthernetPopular architecture Contention Based.
  10, 100Mbps or Gigabit. Carrier detection access
  method. Uses baseband All capacity of
  transmission medium to one communication Channel
• Token Ring 4, 16mbps. Uses Tokens to access the
  medium.
• FDDI Dual Rings. 100Mbps. Up to 100Km wide LANs
  are possible.

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• Broadband Multiple channels of communication on
  one Transmission media.
• Ex Cable, ISDN, DSL
• Bandwidth Capacity of medium to transmit data.
  Like how big a pipe. Bits per sec. Bps

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• Ethernet Technology Shorthand
• 10BASE2
• 10 Bandwidth, 10 MBPS
• BASE Baseband
• 2 Type of Medium, Thin Coaxial,
• Segment length at most 185 meters

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• 10BASE5 Thick Coaxial. Segment length at most
  500 meters
• 10BASET (Unshielded Twisted Pair)
• 100BASET (Unshielded Twisted Pair)
• 10BASE-FL
• 100VG-AnyLAN or
• 100BASE-VG

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• Direction of Communication
• Simplex One way Radio, TV
• Half-Duplex Two way, but one way at a time. CB
  radio
• Full-Duplex Two way. Phone, Computers.

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• Analog Data Continuous Data. Measurement of
  data.
• Radio waves, phone voice.
• Digital Discrete data 0, 1
• 1
• 0

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• To transmit data first data must be converted
  into digital form.
• To send MBA620, we need to convert each one of
  the letters and numbers into digital form.
• How to convert M into sequence of 1s and 0s.
  This conversion is called encoding.

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• Encoding Agreed on method of representing
  characters we use by a sequence of bits.
• Conventions for Encoding
• ASCII 7 bits for each character
• Extended ASCII 8 bits/char
• EBCDIC 8 bits/char
• Unicode 16 bits/char.
• How many characters? (216 65,536)

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• Transmission Types
• How many channels of communication to transmit
  data?
• Serial Transmission 1 channel of communication.
  Bit after bit after bit.
• Parallel Transmission Many simultaneous
  transmissions of data.

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• To transmit 1100110101001
• Serial 1, then 0, then 0, then 1, then 0, ..
• Parallel simultaneously many channels
• 1 ? 1
• 0 ? 0
• 1 ? 1
• 0 ? 0
• 1 ? 1
• 0 ? 0
• 0 ? 0
• 1 ? 1

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• Everything else being the same, which
  transmission is faster?
• In the computers in front of us, what are serial
  and parallel devices?
• How can we tell which is which?

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• Transmission Mode
• Asynchronous Each character transmitted
  individually. Start bit and stop bit to indicate
  when the transmission of character begins and
  ends.

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• Synchronous Combining data into blocks improves
  transmission rate. Clocking mechanism to indicate
  beginning of transmission.
• Asynchronous Each character sent individually.
  Start bit and stop bit.
• Inefficient - too much overhead.

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• Transmission Problems
• Impulse Noise EMI, RFI. Outside noise distorts
  signal. AM Radio signal during vacuum cleaning,
  lightning
• Attenuation Weakening of signal as it travels
  the medium (wire).
• Crosstalk Interference caused by adjacent
  wires.
• Shielding the cable will help many problems
• These are problems due to sending electrical
  signals over a metal wire.
• Will these problems occur if light pulses are
  sent over a fiber optic cable?
• Additional problems of fiber-optic cables.

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• Error Detection
• Parity Parity bit added to data to tell even or
  odd 1s
• Even Add 0 to data if even of 1s. 1 otherwise

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• A 01000001 Even 1s
• Transmit 010000010
• I 01001001 odd 1s
• Transmit 10010011
• Error if A is received as
• 010010010 why?
• Most Reilable Cyclical Redundancy Check (CRC).

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• Carrier Wave Neutral wave used to transmit data.
  
• Carrier wave is modulated (changed) to transmit
  information
• Amplitude Modulation Strength of the wave
  decreased to indicate a 1
• Normal Strength indicates 0
• Frequency Modulation Frequency increased to
  indicate 1.

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• Phase Modulation Frequency or amplitude not
  changed. Instead Phase is changed.
• A Complete cycle is 360 degree phase.
• No phase shift 0
• 180 degree phase shift 1
• Baud Number of signals per second.
• Typically 1 bit per baud.

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• Baud Rate Bits/sec.
• If 1 bit is transmitted per second, it is the
  transmission rate.
• Phase shift modulation allows for more than one
  bit to be transmitted during baud.

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• Modem Converts analog data to digital data.
• Transmitting Analog Data Amplitude, Freq and
  phase Modulation

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• Public Switched Telephone Networks
• Leased Lines T1, T3, Digital Service, Switched
  service.
• T1 1.544Mbps, T3 45 Mbps

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• Basic ISDN
• 2 B channels _at_ 64kbps
• 1 D channel _at_ 16kbps
• Primary ISDN
• 23 B channels, 1 D _at_ 64

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• Network ProtocolsOSI Model
• Application Comm. Comp of applic
• Presentation Code formatting, conv.
• Session establish, manage, term. sess
• Transport end to end connectivity
• Network Interface networks, deliver
• Data link Connection, access to wire
• Physical Physical Structure, bits,

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• Transmission Media
• UTP Unshielded Twisted Pair.
• STP Shielded Twisted Pair.

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• Connectivity Devices
• NIC Network interface Card
• modem.
• Hub or concentrator
• Switch
• repeater and regenerator
• Bridge Segments LAN.
• Router Sends data to internetwork
• gateway, firewall, ..

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• In broadband how to transmit multiple channels on
  one medium.
• Multiplexing
• Frequency
• Time division
• Statistical Time Division

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• Network Models
• Server Based Client/Server.
• Unix (sun, IBM, HP, ..) Windows NT (server,
  Workstation) Novell
• Netware ...
• Peer-to-peer (workgroup) Win 3.1, win 95, win 98

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• Peer-to-peer Resources distributed throughout
  the network. Each computer both provides and
  receives services.
• User of each PC responsible for administering,
  sharing and security of that computer.
• Relevant for small companies.

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• Client/Server Computing Resources located on a
  central server or group of servers. Client
  accesses resources on the server.
• Efficient Resources concentrated.
• Clients thin (lower hw config.)
• File server, Print server, application servers
  (web, SQL, )

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• Client Server Security, administration are
  improved and resources are centralized.
• Scalability Ability to gracefully increase or
  decrease the size of the network.
• Client server networks are scalable.