Comp Sci 7

Conf. between router and device, and device and device is needed.

Concept of networking is that 2 or more entities(devices) that are able to connect to each other

Network Classification

• Geographical Area: PANs, LANs, WANs, etc.
• Design: Peer to peer, client to server
  • Client to server is the most important
  • Peer to peer works with just simple connections (computer to computer)
• Layout: Topology (Bus, Start, Ring, etc.)
• Protocols: TCP/IP, HTTP, HTTPS, etc.

Topologies

• Ring
  • Each device is connected to each other in circular format.
• Mesh
  • Different types of connections: they cross over.
• Star
  • Very common
• Fully Connected
  • Considered a hybrid topology
• Line
  • Adv. connection between devices very quick
  • DisAdv. if one connection fails, the whole network breaks.
• Tree
• Bus

All these topologies have advantages and disadvantages.

Most common: combination of star and tree.

Protocols

Many types of models, for different ways of transport

• TCP/IP Model:
  • Application
    • Person A send email to B. The application layer. The data to be sent is found in the application layer
  • Transport
    • How is the data transferred?
  • Internet
    • Address of device sending + address of device receiving
    • DIfference between IPv4 and IPv6:
      • v4: 32 bit address
        • Number of ip addresses running out
        • uses 1010
        • Older
      • v6: 128 bit address
        • Uses hexadecimal numbers?
        • uses 1010 + hex
        • Newer Both used at the same time
  • Link
    • Type of transmission media in which this data is sent.
    • Maximum distance of bluetooth: 5m
    • Ethernet cable is the most popular link protocol. There are two types:
      • UTPC - Unshielded Twisted Pair Cable
        • Set of 4 pairs of twisted cables.
        • In the middle, there is usually a separation. This results in 2 more types of cables:
          • CAT5
            • Doesn't have the separator in the middle.
          • CAT6
            • Has separator. This is used to defend against interference
      • STPC - Shielded Twisted Pair Cable
      • Ethernet cables are generally 100m viable length!!!
    • Another Link protocol is Fibre-optic cables, different types for different needs:
      • Single Mode
        • One packet of data at a time
        • Sends 1 packet of data at a time.
        • Longer range and faster
      • Multi Mode
        • Multiple packets of data at a time
        • Can send more data in shorter period of time
        • Shorter range and slower
      • e.g. in building to building, distance not that fast, so can use multi mode, in school to use, distance long, so use single mode
    • Another one is coaxial cables
      • Thick diameter of copper cables with multiple layers of protection
      • This is very expensive, so only used for specific cases!
  • The reverse way is how someone receives the data!!!
    • This reverse way are called the protocols.
    • Wireless Examples:
      • Broadcast Satellite
      • Microwave
        • Main Disadvantage, there has to be a direct, clear line between the 2 devices. If there is an object obstructing the transmission, the data is damaged(?)
      • Cellular
        • Tower provides access to multiple mobile devices. This tower connected to another tower, which provides access to other mobile devices, etc.
        • This is called cellular, because one tower connected to multiple devices is one cell.
      • WiFi
        • Device that provides access in a small area of connectivity.
• OSI Model

Hardware

• Typically, networking hardware includes:
  • Routers
  • Bridges
  • Switches
  • Hubs
  • Repeaters
  • Gateways

Devices:

• Computer
• Printer
• Wireless tablet
• WAP
• 3 things in a device (gateway):
  • Modem (see below)
  • Firewall
    • Software that filters packets of data that come into a local network
  • Router

Bridge

• "like a switch" (this is me speaking now) "for networks"
• Receive messages distributed through a network and sends to other networks.
• Connects network segments within a domain together.

Switches

• Switches have 5-48 ports. 24 ports is common.
• Switches connect many devices to each other in a network.
• Routers send and receive data from another network to the switch, switch sends and receives this data to other devices.

Modem

• Converts analogue data to digital data, and vice versa.
• Comes from "Modulate, Demodulate".
  • I.e. convert one type of data to another, vice versa

Router

• Send packets of data to other networks

Packets of data:

• Packets are sent in bytes!
• Bytes are 8 bits!
  • Bits are binary numbers.
• e.g. 1 packet could be 01010101
• All this numbers are just electrical inputs sent through copper cables. It comes out as ones and zeroes, but we aren't actually transmitting ones and zeroes.
• 1 - ON
• 0 - OFF
• During an electrical storm, and using a satellite, there is a chance that the data is received differently.
• e.g. from 01010101 to 01010010
• This is called a bitflip, and computers have evolved to fight against bitflips. For example, if a computer cannot recognise a packet, it will return the packet.
• Even parity: N(ones) is the same
  • Odd parity: N(ones) is not the same
• Lets say packets were even parity, then knowing what the parity is, a computer can check the packet and see whether its still even parity.
  • This has flaws. Let's say that a packet has 3 ones. Bitflips can occur that maintain 3 ones. This means the packet is not returned, if using even parity.

Network Diagram

Important! Use Cisco System for default diagrams.

VERY IMPORTANT! Learn Cisco Diagrams!!!!

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