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Networking and TeleCommunication

Telecommunication is the exchange of data or instruction over a distance using signals or electromagnetic waves.

  • Devices used in telecommunication systems are known as nodes.

Data communication is the telecommunication which involves computers and computer network.

Data Transmission/Communication Mode:​

Transmission mode refers to way in which data communication occurs based on direction of transfer.

  • There are three modes:
    • Simplex: Transmission of data takes place in a single direction. E.g: Radios, Televisions etc.
    • Half Duplex: Transmission of data takes place in both directions but only one direction at a time.
    • Full Duplex: Transmission of data can take place in both direction simultaneously.

Components of data communication:​

  • Message: Data/information that is to be communicated
  • Sender: Computer/Computing device that creates and sends the message
  • Receiver: Computer/Computing device that receives the message
  • Medium: Channel/path through which message is transferred
  • Protocol: Set of rules followed by sender and receiver.

Communicaton/Transmission Media​

A channel or path through which data and information are transmitted between connected devices in a network environment is called communication media.

  • Two types:
    • Guided / Wired / Bounded
    • Unguided / Wireless / Unbounded

Guided Transmission Media​

Guided transmission media uses cable or wire to transfer data and information among computers.

  • Types:
    • Co-axial (BNC connector)
    • Twisted pair (RJ-45 connector)
    • Fiber Optics (ST, SMA, SC connectors)

Co-Axial Cable​

Consists of a inner conductor surrounded by an insulating layer and again surrounded by conducting shield.

  • Advantages:
    • Higher bandwidth as compared to twisted pair
    • Better shielding
    • Good noise resistance
    • Lower error rates
  • Disadvantages:
    • More expensive than twisted pair

Twisted Pair Cable​

Consists of multiple pair of copper wires twisted together and insulated with plasic.

  • Types:

    • Unshielded Twisted Pair: These don't have a metallic shield/sheath.
    • Unshielded Twisted Pair: These have a metallic shield/sheath.

  • Advantages:

    • Relatively easy to implement and terminate
    • Least expensive

  • Disadvantages:

    • Poor noise immunity
    • High attenuation
    • Lower bandwidth

Fiber Optic Cable​

Made up of plastic or glass fiber to transmit data.

  • Advantages:

    • High bandwidth and Fast
    • low power loss
    • Longer distance support
    • Good resistance
    • Low attenuation

  • Disadvantages: -

    • Most Expensive
    • Difficult to join (splice)
    • Easily breakable

Unguided transmission media​

Unguided transmission media doesn't use wire or cable for data transmission.

  • Types:
    • Radio Wave
    • Micro Wave
    • Satellite Communication

Radio wave​

High frequency wave(30MHz to 1GHz) wave that can travel long distance.

  • Data is changed to signal with FM(Frequency modulation), AM(Amplitude modulation) and PM(Phase Modulation)

Microware​

Super High Frequency wave(1GHz to 40GHz) wave that can travel short distance(30 to 40KHz) and need repeaters.

  • Needs tall towers

Satellite Communication​

Uses artificial satellite stationed in space for this specific purpose.

  • Earth station communicates with the satellite.

Other unguided mediums​

  • Infrared: short range, used in remotes
  • Bluetooth: short range, used for short range communication (mostly to connect peripherals). (2.4GHz)

Computer Network​

Computer network is a group of two or more computers and devices connected to each other through wired or wireless media to share resources.

  • Advantages:

    • Can be used to share hardware(printer, storage devices etc.).
    • Can be used to share data and software.
    • Can be used to communicate.
    • Supports central control and administration.

  • Disadvantages:

    • Malware can be transferred.
    • Skilled manpower is required to setup and manage.
    • Initial setup cost is high.
    • Cybercrimes can occur and need to be handled.

Elements/Componentts of Computer Network​

  • Hardware Components:
    • Computer System:
      • Server: Provides service/resources and controls and manages other computers on the network
        • File Server
        • Database Server
        • Print Server
        • Network Server
        • Mail Server etc.
      • Workstation: Uses resources of the network
    • Network Adapter/NIC card: Network Interface card provides ports to connect computer to network. In can come built-in or needs to be placed on expansion slot on motherboard.
    • Connectors: Used to connect communication media with network devices.(BNC, RJ-45, ST)
    • Network devices: Devices used for setting up network like hub, switch etc.

Network Devices​

Hub​

Networking device with multiple port that transmits received data to all connected computers including sender.

  • Passive hub: No electricity and no amplification.
  • Active hub: Requires electricity and amplifies signal

Switch​

Networking device with multiple port that can determine source and destination of data packets.

  • Switch is upgrade of hub.

Hub is cheaper but it is less efficient and slower as it broadcasts packets to all connected computers and is half duplex.

Bridge​

Bridge connects two networks with similar/same protocol.

  • Bridge inspects incoming signals (MAC address) and decides whether to forward or discard it making it efficient.

Gateway​

Gateway connects two networks having different protocol.

  • It is like a dedicated server that acts as protocol converter.

Router​

Router joins multiple wired or wireless networks together and routes(determine path and send) data based on IP address.

Repeater​

Repeater is a network connectivity device that regenerates/amplifies weak signals.

MODEM​

Modulator Demodulator is a network device that transfers data through telephone wire.

  • Modulation: Conversion of digital signals to analog signals.

  • Demodulation: Conversion of analog signal to digital signal.

  • Modulation is required as telephone wire can only transfer analog signal and demodulation is required as computers understand digital signal.

Network Topology​

Network topology is the inter-connection pattern of network components.

  • Types:
    • Bus topology
    • Ring Topology
    • Star Topology
    • Mesh Topology

Bus Topology​

This topology uses a segmeent of single cable to connect nodes. This cable is called bus.

  • Terminators are attached at start and end.

  • Advantages:

    • Easy to setup
    • Easy to expand
    • Cheap
    • Easy to understand

  • Disadvantages:

    • Single point of failure(If main cable breaks, whole network malfunctions)
    • Network performance degrades with heavy traffic.

Ring/Loop Topology​

In this topology, a closed loop is formed by computers.

  • Data is transmitted in one direction(clockwise or anticlockwise).

  • Advantages:

    • Cheap to install and expand.
    • Each computer acts as client or server.

  • Disadvantage:

    • If a node fails, whole network is disturbed.
    • Difficult to troubleshoot.
    • Adding or removing node disturbs the network.

Star Topology​

Type of topology in which all nodes are connected to a central device (hub/switch) through a cable.

  • Advantage:

    • Fast
    • Easy to troubleshoot
    • Easy to setup and modify
    • Node failure doesn't disturb network

  • Disadvantages:

    • Initial cost is high due to hub/switch.
    • If hub/switch fails, network fails.

Mesh Topology​

In this each computer is connected to every other computer.

  • Advantage:

    • Fast
    • Privacy is maintained

  • Disadvantages:

    • Requires lot of wires
    • Not practical for large number of devices.

Hybrid topology can be made by combining different topology.

Types of Computer Network(Based on size)​

  • Three types:
    • Local Area Network: Small network limited within a small area like a room, a building, school, college etc. Eg. A buildings CCTV network.
    • Metropolitan Area Network: Network mostly within cities and is used for sharing of regional resources. Eg. Traffic light network of a city.
    • Wide Area Network: Very large network that covers country, countries or even the world. Eg. Internet.

Network Architecture/Model​

Network Architecture specifies how computers on the network interact and communicate with each other.

  • Types:
    • Client-Server Model: There is at least one server that provides services and some clients/workstations that receive service from server. Servers are usually powerful computers and can administer the network and share resources.
    • Peer to Peer Model: There is no server that manages the network or share resources. Each computer connected is called peer and each per has equal rights.
    • Centralized Network Model: Here all client nodes are entirely dependent on the central server.

Peer to Peer models are easy to set up but lack security, need individual hardware and software, and have limited expansion and network performance.

Centralized Network save a lot of resource and are highly secure and administerd but have single point of failure.

Internet and its services​

Internet is a WAN that connects computers all over the work based on TCP/IP protocol suite.

  • Services of Internet:
    • WWW: Interlinked collection of hypertext documents and multimedia contents available on internet.
    • Email: Used to send and receive messages electronically throught the Internet.
    • Telnet: Allows user to use a remote computer through internet.
    • FTP: Protocol that lets file transmission between computers on the internet.
    • Search Engine: Communication program that finds documents based on keywords. Eg. Google.
    • IRC: Allows real time communication.
    • Online Banking: Financial transactions through internet.
    • E-commerce: Bying and Selling of products through internet.