networks

Created by: cal14
Created on: 22-02-18 18:11

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networks
- network typoligys
  - bus
    - a back bone with individual connections to each computer
      - cheap, if the cable breaks no computers have access
  - star
    - a central switch with individual connections to each computer
      - cheap, if one connection breaks only the connected computer is disconnected
  - ring
    - one connection that loops to all the computers
      - cheap if the ring breaks all computers cant communicate
  - partial mesh
    - most computers are connected to most others
      - it is cheaper than full mesh and if one connection breaks then it is OK
  - full mesh
    - each computer has a switch connected to each outer switch
      - expensive but if one connection breaks all computers still have access
- wired networks
  - transmission media
    - fiber optic cables
      - fastest transmission media
    - twisted copper pairs
      - supports full duplex used for ethernet
    - coaxal
      - original wires
  - LAN hardware
    - router
      - send data between WAN's uses IP
    - switch
      - routs packets in a LAN only sends it where it is needed uses mac
    - wap (wireless access point)
      - allows wireless access to the network
    - nic (network interface card)
      - lets computers access a network
    - transmission media
      - fiber optic cables
        fastest transmission media
      - twisted copper pairs
        supports full duplex used for ethernet
      - coaxal
        original wires
    - hub
      - a dumb switch which just broadcasts data to all its connections
  - network models
    - peer to peer
      - all peers have equal power and have own files
        no specialist needed
        
        no single point of failure
        
        cheap to setup
        
        less secure
        
        have to backup themselves
        
        can be difficult to maintain files
    - client sever model
      - a central sever that controls files and network traffic etc
        more secure
        
        easier to manage
        
        easier to backup
        
        easier to update and install programs
        
        can be expensive
        
        requires specialist
        
        a single point of failure
- wifi
  - wireless fidelity
    - frequency and channels
      - each channel has a range of 22mhz
      - channels overlap and there are 14 channels in the 2.4mhz range
    - advantages and disadvantage
      - allows for free movement
      - easy to set up
      - slower speeds
      - convinient
      - relies on signal strength
      - can handle large numbers of users
      - can be obstructed
      - easy transfer of infomation
      - less secure than lans
    - encription
      - a device can listen into your wifi traffic
      - the wifi creates a key and uses this to encrypt data the key can be used to decrypt data
      - hand shake protocal
- layers
  - layer 2
    - data link layer
      - creating and routing on a LAN error checking
        Ethernet , mac
  - layer 5
    - session layer
      - Untitled
        Untitled
  - layer 3
    - network layer
      - routing packets on a lan
        ipv4 ,ipv6
  - layer 6
    - presentation layer
      - encription
        ssl
  - layer 1
    - physical layer
      - methods of encoding bits
        coax, fibre , wireless
  - layer 4
    - transport layer
      - creating and sequencing packets on a wan, error checking
        tcp,
  - layer 7
    - application layer
      - web browsing, email, file management
        http, https, ftp, pop, smtp, imap

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