Networks

Networks

1. What is a network?

   • A network is a collection of computers that are connected together
   • A computer that is not in a network is called a stand-alone computer
   • We connect computers in a network so they can share resources and communicate easily
   • Examples: -Computers connected in a school -The Internet

2. Types of networks

   • LANs
     • Local area network
     • A network that covers a small geographical area such as a single building or a small site of buildings
     • Examples: -Schools -Small businesses
   • WANs
     • Wide area network
     • A network that covers a large geographical area, such as a several branches of an organisation, a city, a country or even several countries
     • Example: -The Internet
   • Client-server network
     • A network that contains servers and clients
     • Each computer that is connected to the network that is available for general use is a client. They request data and services from servers
     • The servers are the central computers in the network. They provide services and data for the clients, and allow a variety of functions to be performed on the network from a central computer instead of each individual computer
     • Some of the functions that a server allows include security, data storage, backups, managing Internet connections and providing email services
     • Servers are expensive
   • Peer-to-peer
     • Each computer is a peer
     • The network does not have a central server managing the network- the management is the responsibility of each individual peer
     • Each computer is able to share files and resources with other computers in the network

3. Packet switching

   • When we send data over the Internet, it is divided into 'packets' and sent over the network- this is called 'switching'
   • The packets contain a header, a payload and a trailer
   • The header contains the sender's IP address, the receiver's IP address, the packet number, the length of the packet and the protocol
   • The payload contains the data
   • The trailer contains the end-of-packet marker and error checking

4. Virtual networks

   • A virtual network is one that is created using software
   • You can use virtual network to keep personal data safe
     • These virtual networks are called 'virtual private networks' (VPN)
     • They can be set up in a large WAN such as the Internet
     • You can log into your VPN from anywhere in the world and use your own private network to communicate personal data
     • The packets of data that are sent using a VPN have an extra element to them- it acts like an outer layer of protection that means that only the VPN can understand the packet

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