The Internet and Network Topologies

• The Internet

  A network of networks- it's a WAN which connects devices and networks from all over the world.
• What protocol is the internet based around?

  TCP/IP
• The World Wide Web (WWW)

  A collection of websites that are hosted on web servers
• How is the World Wide Web (WWW) accessed?

  The HTTP protocol
• What sort of network is the WWW an example of?

  A client-server network
• URLs

  Are addresses used to access web servers and resources on them
• What is this an example of: http://www.example.com/folder/file

  URL
• What is the domain name linked to?

  The IP address
• IP Address


  A unique identifier given to a device when it accesses an IP network.
• Domain Name Service (DNS)

  A DNS is used to translate website domain names into IP addresses
• Why is a Domain Name Service used for website domain names?

  So you don't have to remember IP addresses to access websites- you can use the domain name instead
• What are the servers called that store IP addresses and the matching domain name?

  Domain Name Servers
• What happens if a DNS server doesn't have an IP addresses associated with a particular domain name (a DNS miss)?


  It passes the request onto another more authoritative DNS server. An error is sent back if no match is found
• A Domain Name Service (DNS) is made up of multiple Domain Name Servers.
• Star Topology

  All the devices are connected to a central switch or server that controls the network
• Star Topology

  
• Full Mesh Topology

  
• Partial Mesh Topology

  
• Star Topology- Pros:

  • If a device fails or a cable is disconnected, the rest of the network is unaffected
  • It's simple to add more devices to the network
  • Better performance- data goes straight to the central device so all devices can transmit at once and there are few data collisions
• Star Topology- Cons:

  • In wired networks, every device needs a cable to connect to the central switch or server. This can be expensive
  • If there is a problem with the switch/server, the whole network is affected
• Full Mesh Topology

  Every node is connected to every other node in the network
• Partial Mesh Topology

  Many connections between nodes
• Mesh Topology- Pros:

  • Highly robust as the network will automatically find a different route if there is a fault with one connection or node.
  • Data can be transmitted from several devices simultaneously. The network can cope with high traffic.
  • Local networks run faster than in a star network because data does not have to travel via a central switch
• Mesh Topology- Cons:

  • The network is very expensive to set up as it is difficult to establish the connections
  • Self-maintenance and network administration is complex; it may be difficult to expand the network
• Cloud computing (the cloud)


  The use of the Internet to store files, access software and provide increased computing power.
• Cloud Advantages:

  • Flexible storage is offered so you can scale your requirements up and down overnight
  • You do not need to purchase and maintain expensive hardware
  • The Cloud storage provider is responsible for the security of your data and regular backups
  • One cloud storage centre is more environmentally friendly than millions of individual servers
  • You do not need any networking skills or maintenance workers
• Hosting- A web hosting company will host websites, files and databases.
• Describe the role of the switch in the star topology

  A switch connects devices together.

  It receives data from all devices in the network.

  It directs data to its destination.
• Explain the difference between the Internet and the World Wide Web.

  The Internet is the infrastructure (collection of networks), and WWW is the web pages stored on servers