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Networking. U2M3 Network Devices. Objectives. List the basic network hardware Describe various Transmission Media Explain the function of various network hardware Identify the OSI layer that the equipment resides. OSI layers.

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Network Devices

  • List the basic network hardware
  • Describe various Transmission Media
  • Explain the function of various network hardware
  • Identify the OSI layer that the equipment resides
osi layers
OSI layers
  • Application (Layer 7)Presentation (Layer 6)Session (Layer 5)Transport (Layer 4)Network (Layer 3)Data Link (Layer 2)Physical (Layer 1)
  • All People Seem To Need Data Processing
  • Please Do Not Through Sausage Pizza Away
  • A Node is any device on a network that is accessed directly.
    • server
    • workstation
    • printer
    • scanner
    • or any other kind of peripheral
  • A node has
    • an unique name or IP address so the rest of the network can identify it.
physical layer 1 network devices
Physical (Layer 1) –Network devices
  • Transmission Medium
  • Connectors
  • HUBS
  • Repeaters
  • Network Cards
  • Modems
  • Data Transmission via : electric voltages, radio frequencies, pulses of infrared or ordinary light
data flow
Data Flow
  • Simplex transmission
    • One direction only
      • Television and radio
  • Half-duplex transmission
    • Both direction – one direction at a time
      • CB radio, terminal
  • Full-duplex transmission
    • Both directions at the same time
      • Telephone, computer to computer
  • Asynchronous transmission
    • Start/stop bits for character synchronization
    • Mark (1or stop) /space (0 or start ) bits for bit synchronization
    • Simple, inexpensive, slow speed transmission
    • For personal computer
  • Synchronous transmission
    • Clock circuitry
    • One to four synchronization characters for each block of data
    • Large amount of data on dedicated line
transmission medium
Transmission Medium

Any material that is capable of carrying one or more signals

  • Twisted Pair
  • Coaxial Cable
  • Fiber Optics
  • wireless Signals
twisted pair cabling
Twisted pair cabling

Shielded and Unshielded.

  • Unshielded twisted pair (UTP)
  • Category 3 - Data to 10 Mbps (Ethernet)
    • Ethernet specification -10BaseT
  • Category 4 - Data to 20 Mbps (Token Ring)
  • Category 5 -Data to 100 Mbps (Fast Ethernet)
    • Ethernet specification -100BaseT
rj 45 connector
RJ-45 connector
  • The standard connector for twisted pair cabling is an RJ-45 connector
coaxial cable
Coaxial Cable
  • Coaxial cabling has a single copper conductor at its centre
    • Ethernet specification - 10Base2
  • resistant to signal interference.
  • supports greater cable lengths between network devices
  • Cable television (CATV) network wiring often uses coaxial cable
bayone neill concelman bnc connector
Bayone-Neill-Concelman (BNC) connector
  • connector used with coaxial cables
    • T-connector,
    • barrel connector
    • terminator
fiber optic
Fiber optic
  • consists of a centre glass core surrounded by several layers of protective materials
    • Ethernet specification -10BaseF
  • Transmit
    • light rather than electronic signals
    • signals over much longer distances
  • at greater speeds
    • 100Mbps to 1Gbps.
fiber optic connector
Fiber Optic Connector
  • ST connector
    • It is barrel shaped, similar to a BNC connector
  • SC connector
    • It has a squared face
communications media summary
Communications Media Summary
  • Twisted pair (copper cable)
    • used in telephone network and LANs
  • Coaxial cable
    • high quality, well insulated cable
  • Fibre optic cable
    • sends pulses of light rather than electricity
  • Microwave
    • almost line of sight (can be up to about 30 miles apart)
  • Communications satellite
    • in geosynchronous orbit (rotating at the same speed as earth, therefore stationary relative to Earth)
  • FireWire also known as IEEE 1394
    • transfers information between digital devices, especially audio and video equipment.
    • is fast -- speeds up to 800 Mbps.
wireless transmission media
  • Wireless Transmission media send communication signals through air or space using radio, microwave, and infrared signals.
  • Has a transceiver/antenna to send and receive the data.
  • Advantage
    • more convenient than installing cables
    • where installing cables are impossible.
  • The wireless transmission media
    • Satellite
    • Microwave
    • Wireless fidelity (WiFi)
  • This makes connectivity available via satellites that orbit the earth
    • provides access to users in remote areas
  • A communication satellite is a space station that receives microwave signals from an earth-based station, amplifies (strengthens) the signals, and broadcasts the signals back to earth over a wide area to any number of earth-based stations.
  • The earth-based stations -
    • microwave stations.
    • smart phones
    • GPS receivers,
  • Communication satellite’s transfer data rate is 1Gbps.
  • Uplink is the transmission from an earth-based station to a satellite.
  • Downlink is the transmission from a satellite to an earth-based station.
  • Microwaves are radio waves that provide a high-speed signal transmission
    • maximum rate of 150 Mbps
    • use line-of-sight transmission
    • fixed wireless, involving sending signals from one microwave station to another.
  • IEEE 802.11x.
    • 802.11a,
      • up to 54 Mbps
      • Uses 5 GHz range
    • 802.11b ,
      • 11 Mbps
      • Uses 2.4 GHz range
        • Interference
    • 802.11g,
      • 54 Mbps
      • Uses 2.4 GHz range
    • 802.11n
      • over 100 Mbps
      • multiple wireless signals and antennas (MIMO technology)
  • A hub is central device that (seldom still used today)
  • provides a common connection point for nodes on the network.
  • broadcast messages
hubs functions
Hubs - Functions
  • When a signal is sent from a computer, it is
    • received by the hub
    • make a clean, strong copy of the signal.
    • Broadcast
      • Retransmitted to all other computers connect to it.
    • accepted only by computer the signal is addressed.
hubs issues disadvantages problems
Hubs - Issues / Disadvantages/ Problems
  • If the hub goes down, the whole network goes down.
  • Broadcasting messages
    • slow down network
      • generate lot of traffic
    • Lowers security
  • Amplifies the input signals and retransmits.
  • It Is used to extend the range of a network segment.
network interface card
Network Interface Card
  • NICs play an important role in connecting a computer to the physical part of the network
  • A modem (Modulator DEModulator) is a device that modulates an analogue carrier signal to encode digital information, and also demodulates such a carrier signal to decode the transmitted information.
types modem connections
Types Modem Connections

Telephone service

  • Dial-up Modems

Broadband Telephone Service

  • Integrated Services Digital Network (ISDN)
  • DSL (Digital Service Line)

TV service

    • Cable modem
dial up modems
Dial-up Modems
  • Features
    • Analogue
    • dial-up connections
      • normal phone lines
      • dial-up service
    • data rate up to 56 Kbps
    • voice or data
      • on the phone or internet
        • Connect drops when phone rigns
integrated services digital network isdn
Integrated Services Digital Network (ISDN)
  • Features
    • dial-up service
    • Digital
    • special ISDN telephone line
    • Data rate use 64Kpbs channels
      • combined channels for higher speeds.
digital service line dsl
Digital Service Line (DSL)
  • Features
    • Digital
    • Telephone lines
    • Always connected
    • Data rate up to 6 Mbps
    • Use both data and voice (be on the phone and internet)
cable modem
Cable modem
  • Features
    • Analogue or digital
    • Uses coaxial cable
    • Always connected
    • data rate up to 30 Mbps
data link layer 2
Data Link (Layer 2)
  • Network Interface Card
  • Switches – uses MAC address
  • Bridges
network interface card1
Network Interface Card
  • a NIC operates at both layer 1 and Layer 2.
  • At Layer 2
    • the NIC MAC address are used by switches to make connections between nodes
  • A switch is a network device that connects a number of computers together to make a LAN.
  • Function
    • each computer has its cables plugged into it
    • on receiving a message, it checks who it is addressed to, and only sends it to that specific computer.
  • Is an ‘intelligent’ device
    • Compared to a hub
    • networks that use switches are more secure than those that use hubs,
    • more expensive than hubs.
  • The typical use of a switch
    • At the centre of a star network (or as part of a hybrid network)
  • A bridge is a network device that typically links together two different parts of a LAN.
bridge functions
Bridge Functions
  • analyze incoming data packets
    • Determine which segment of the network to send the given packet.
  • filters data traffic at a network boundary
    • reduce the amount of traffic on a LAN
      • divided into two segments
network layer 3
Network (Layer 3)
  • Routers - uses the IP address
  • Layer Three switches (brouter)

A network device that

  • is used to connect together two or more networks.
    • a LAN to a WAN
router functions
Router Functions
  • forwards data packets across and between computer networks.
    • different from a switch which works within a single network
  • selects the fastest available path
    • For data packets to reach their destination
  • allows multiple computers to share a single high-speed (Internet) connection
  • A wireless router is a router and wireless switch combined.
  • It links a wireless LAN to a WAN
transport layer 4
Transport (Layer 4)
  • Gateways
    • Proxy Server
  • Firewalls
transport layer 41
Transport (Layer 4)
  • Gateways
    • Proxy Server
transport layer 42
Transport (Layer 4)


  • are very intelligent devices
    • can be a computer running the appropriate software


  • connect and translate data between networks with different protocols or architecture,
    • much more complex than a normal router
a proxy server
A proxy server
  • is a computer setup to share an Internet connection.
  • additional software can be easily installed
      • such as anti-virus,
      • web filtering

FunctionOther computers request a web page via the proxy server.

    • The proxy server gets the page using its Internet connection, and passes it back to the computer who asked for it.
  • A firewall is a device, or software that protects a network from external threats
    • Hackers
  • Normally placed
    • between the LAN and the Internet connection.
firewall functions
Firewall Functions
  • inspects all the information which is passed over the system
  • determines if it is a threat or not based upon a variety of RULES.
    • prohibits forbidden information from passing though
    • allows approved information to pass