COMPUTER NETWORKS

• Telecommunication


  Communication at a distance
• Data


  Information presented in whatever form is agreed upon by the parties creating and using the data
• Data communications


  The exchange of data between two devices via some form of transmission medium such as a wire cable or wireless
• Components of data communication

  • Sender
  • Receiver
  • Communication medium/media
  • Message
  • Protocol

  
• Protocol (human communication)


  Includes: identified sender and receiver, common language and grammar, speed and timing of delivery, confirmation or acknowledgement requirement

  
• Protocol (network communication)


  Includes: message or data encoding, message formatting and encapsulation, message timing, message size, message delivery options

  
• Data representation

  • Text
  • Numbers
  • Images
  • Audio
  • Video
• Data flow

  • Simplex
  • Half-duplex
  • Full-duplex
• Network


  A set of devices (nodes) connected by communication links. A node can be a computer, printer, or any other device capable of sending and/or receiving data generated by other nodes on the network.

  
• Network devices


  • Also known as networking hardware, they are physical devices that allow hardware on a computer network to communicate and interact with one another. Examples: Repeater, Hub, Bridge, Switch, Routers, Gateway, Brouter, and NIC.

  
• Switch


  A network device that connects devices in a network to each other, enabling them to talk by exchanging data packets. Switches can be hardware devices that manage physical networks or software-based virtual devices.
• Bridge


  A network device that creates a single, aggregate network from multiple communication networks or network segments.
• Router


  A device that connects two or more packet-switched networks or subnetworks. It serves two primary functions: managing traffic between these networks by forwarding data packets to their intended IP addresses, and allowing multiple devices to use the same Internet connection.
• Modem


  A network device that both modulates and demodulates analog carrier signals (called sine waves) for encoding and decoding digital information for processing.
• Firewall


  A network security device that monitors and filters incoming and outgoing network traffic based on an organization's previously established security policies.
• Types of connections

  • Point to point
  • Multipoint
• Physical topology: Mesh


  • Every device has a dedicated point-to-point link to every other device. A fully connected mesh network has n(n-1)/2 physical channels to link n devices. Every device on the network must have n-1 input/output (I/O) ports. Advantages: Less traffic, robust, secure, easy to maintain. Disadvantages: Need more resources (cable and ports), expensive.

  
• Physical topology: Star


  • Each device has a dedicated point-to-point link only to a central controller, usually called a hub. No direct traffic and link between devices. Advantages: Less expensive, easy to install and reconfigure, robustness. Disadvantage: Single point of failure.
• Physical topology: Bus


  • A multipoint topology where all devices are linked through a backbone cable. Nodes are connected to the bus cable by drop lines and taps. Advantage: Ease of installation. Disadvantages: Difficult reconnection and fault isolation, broken or fault of the bus cable stops all transmission.
• Physical topology: Ring

  • Each device is dedicated point-to-point connection only with the two devices on either side of it. A signal is passed along the ring in one direction, from device to device, until it reaches its destination. Each device in the ring incorporates a repeater. Advantages: Relatively easy to install and reconfigure, fault isolation is simplified. Disadvantage: Unidirectional traffic.
• Physical topology: Tree


  • Integrates multiple topologies together, e.g. a tree topology integrating multiple star topologies onto a bus. Advantages: Point-to-point wiring for individual segments, supported by several hardware and software vendors. Disadvantages: Overall length of each segment is limited, if the backbone line breaks the entire segment goes down, more difficult to configure and wire than other topologies.
• Categories of networks


  • Local Area Network (LAN)
  • Wireless Local Area Network (WLAN)
  • Campus Area Network (CAN)
  • Metropolitan Area Network (MAN)
  • Wide Area Network (WAN)
  • Personal Area Network (PAN)