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The Open Systems Interconnection model (OSI model) is a conceptual model that characterises and standardises the communication functions of a telecommunication or computing system without regard to its underlying internal structure and technology.

This “OSI Model”: is often the best way to describe networking is to use the 7 layer OSI model:

1. Physical layer
2. Data Link Layer
3. Network Layer
4. Transport Layer
5. Session Layer
6. Presentation Layer
7. Application Layer

The Physical Layer

• This, as in the name comprises of all things physical. From computer hardware, cables, printers, all physical networking devices, and all physical servers

• Networking hubs are layer 1.

• The unit of this layer is bits (binary bits)
  • At the end of the day all data in the computer world is transported as bits.

The data link layer

• This layer is where switches, network cards, wifi in the LAN work.

• The addressing scheme for this layer is the MAC address
  • All networking cards including wifi access points have a unique MAC address which is physically hard-coded onto the device.

The Network Layer

• This is the layer that handles LAN to LAN connectivity and routing
  • In fact routers and routing network devices exist in this layer.

• The addressing scheme for this layer is the IP address. This is the main addressing scheme that is used in connectivity throughout the internet. There ate currently two main versions of IP addresses – IPv4 and IPv6
  • IPv4 is very much more widely used, throughout the internet. However, with forever increasing demands for more addresses on the internet it is very much a scheme that is running out, and hence the need for a new scheme.
  • IPv6 is the scheme that is being brought in to replace IPv4. However there are certainly many teething issues - the biggest is that if is not backwards compatible with IPv4.