Networks

Networks

1. General

   • Created when more than one device connected
   • Small chunks of data are data packets
   • Packets sent individually then put back together at destination
   • Protocols control how data transmitted, split and put back together etc.
   • Advantages: share files, internet connection and devices, communication, roaming profile (look at things on network all over the world
   • Disadvantages: reliance on networked resources, expensive hardware, risk of viruses and hacking, specialist staff often required

2. LANs and WANs

   • LAN (Local Area Network) = within building, not always connected to internet
   • WAN (Wide Area Network) = lots of LANs connected, requires media such as broadband cables
   • VPN (Virtual Private Network) = uses internet for secure connection to network e.g. school network from home
   • WPAN (Wireless Personal Area Network) = connect devices to other devices e.g. hotspot phones
   • PAN (Personal Area Network) = same as WPAN but wired e.g. connecting phone to computer

3. Wired and Wireless Connections

   • Wired - connected through Ethernet cables, which connect to Ethernet ports. Need Network Interface Card (NIC)
   • Wireless - need wireless NIC (WNIC), uses radio signals (adapter converts data into radio singal then receiver decodes for computer)
   • Access can be restricted to certain MAC addresses, can encrypt using key that works with WiFi Protected Access (WPA)
   • Advantages of wireless: cheap set-up, connect multiple devices with no extra hardware, not in specific location, no wires
   • Disadvantages of wireless: interference can occur, connection can drop as not as stable as wired, lose quality through obstructions, more open to hacking, slower than wired

4. Device Addresses

   • MAC Address - unique, embedded in hardware (in NIC), cannot be changed, 48 bits
   • NIC - enables device to connect to network, small circuit boards that connect to motherboard
   • Smartphones use GSM (Global System for Mobile Communication) chips to connect to telephone network

5. Types of network

   • Client-server - relationship between computers, client makes service request from server, client dependent on server, server controld security and manages network, data backed on main server
   • Peer-to-peer - no single server, each computer equally responsible for providing data and acting as servers
   • P2P ideal for sharing files, unsuitale for things like booking tickets, and anyone can delete files as they wish

6. Servers

   • Stores data for other computers
   • Web Servers - host websites, handle requests for static info (HTML websites), manage websites on servers (e.g. BBC website)
   • Application Servers - to run web applications (more complex than static),MySQL and NoSQL databases accessed via app server, client sends request to web server which sends request to app server
   • Network Attached Storage (NAS) - storing and sharing files, useful for large files e.g. video, but not for websites or web applications
   • Print Server - makes it easy for devices to connect to printer, removes need for printer driver software or cables
   • Mail Server - stores emails, browser makes requests to mail servers to retrieve messages