Networks

Created by: neilsfriend
Created on: 18-04-18 09:55

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Networks
- LANs + WANs
  - LANs
    - Small geographical area
    - Hardware owned by using organisation
    - Wired or wireless
  - WANs
    - Connects LANs that are in different geographical locations
    - Infrastructure hired
    - Connected using telephone lines, satellite links, radio links
  - Performance
    - Bandwidth, amount of data transferred
    - Wired connections faster, more reliable
    - Choice of hardware and topology
- Hardware
  - NIC, Switches, Routers
    - NICs allow devices to connect to a network
    - Switches connect devices on a LAN
    - Routers transmit data between networks
  - Cables
    - CAT 5e/6, four pairs of twisted copper wires
    - Coaxial, single copper wire, plastic layer + metallic mesh
    - Fibre optic, transmit data as light, no interference
  - Wi-Fi
    - 2 radio frequency bands, 2.4GHz and 5GHz
    - Split into numbered channels, each have small frequency range
    - Performance affected by interference between networks
- Topologies
  - Star
    - All devices connected to a central switch or server
    - If a device fails, the rest of the network is unaffected
    - If the switch/server fails, the whole network's affected
  - Mesh
    - All devices directly or indirectly connected to each other
    - There's no single point the network can fail
    - Expensive as lots of wires needed
  - Bus + Ring
    - Traditional network setups
    - Ring - Data moves in one direction, no collisions
    - Bus - Arranged in a line, data both ways, collisions
- Protocols
  - TCP
    - Transmission Control Protocol
      - Splits data into packets, sets rules for how devices connect on a network
  - IP
    - Internet Protocol
      - Packet switching
  - HTTP
    - Hyper Text Transfer Protocol
      - Used by web browsers to communicatewith webservers
  - HTTPS
    - HTTP Secure
      - Encrypts all data sent + received
  - FTP
    - File Transfer Protocol
      - Used to access/edit files between devices on a network
  - POP3
    - Post Office Protocol 3
      - Retrieve emails from a server. Holds it until it's downloaded
  - IMAP
    - Internet Message Access Protocol
      - Retrieve emails from a server. Holds until it's deleted
  - SMTP
    - Simple Mail Transfer Protocol
      - Used to send emails, transfers emails between servers
- Layers
  - 1. Data Link Layer
  - 2. Network Layer
  - 3. Transport Layer
  - 4. Application Layer

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Networks

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