Skip to content

1.1 Applications

  • Groups of people who interact with the Internet
    • Users
    • Those who create applications
    • Those who operate or manage networks
    • Those who design and build devices and protocols that collectively make up the internet.
  • Classes of applications of the internet
    • Web
      • Webpages
      • Static images, links, text
    • Streaming of audio and video
      • Netflix, youtube.
      • The whole video file doesn't download at once.
    • Real-time Audio and video
      • Zoom, videoconferencing
      • even tighter constraints than streaming

1.2 Requirements

  • Stakeholders and what they would list their requirements for a network
    • Application programmer

      - Services that their application needs

    • Network operator
      • Characteristics of a system that are easy to administer and manage
    • Network designer
      • Properties of a cost effective design
  • Scale
    • A system that is designed to support growth to an arbitrarily large size
  • Link
    • a physical medium that directly connects 2 or more computers on a network
  • nodes
    • Can be computers or other pieces of specialized hardware.
    • pair of nodes are 'point to point'
    • more than 2 nodes are 'multiple-access'
  • Types of networks
    • Direct Links
      • Point to Point
      • Multiple-access
    • Circuit switched
      • Telephone system
      • Optical networking
      • Nodes establish a dedicated circuit across a sequence of links and then allows. Then allows the source node to send a stream of bits across the circuit to the destination node
    • Packet Switched
      • Computer networks
      • Use store and forward
        • Each node receives complete packet, stores in internal memory & forwards complete packet to next node.
  • Network definitions
    • nodes
      • Switches are inside the network
        • implement the network
        • primary function to store and forward packets
      • Hosts are outside the network
        • use the network
        • support users and run application programs
      • Router or Gateway
        • A node that is connected to two or more networks
        • same role as a switch where it forwards messages from one network to another.
      • Address
        • must be assigned to each node on a network
        • a byte string that identifies a node
      • Routing
        • The process of determining systematically how to forward messages toward the destination node based on its address
      • Unicast
        • A source node that sends a message to a single destination node
      • Multicast
        • A source node that wants to broadcast a message to all nodes on a network
        • A source node that wants to broadcast a message to a subset nodes but not all of them.
    • Multiplexing
      • When a system resource is shared among multiple users
      • Synchronous Time-Division multiplexing / STDM
        • Dividing time into equal-sized quanta
        • In round robin fashion, giving each flow a chance to send its data over the physical link.
      • Frequency-division multiplexing / FDM
        • Transmitting each flow over the physical link at a different frequency
        • Similar way that the signals for different TV stations are transmitted at different frequencies over the airwaves