Network Layer Model
Network protocols are divided down into layers. This formalises the idea that some protocols build on / or sit on top of the work being done by other protocols. There are multiple levels to the layer model, for GCSE we only need to know about four of them. Protocols in the higher layers pass data and trigger actions in the layers below it so opeing a page using HTTP in layer 4, causes actions from the TCP (layer 3), IP (layer 2) and finally Ethernet protocols (layer 1):
Advantages of the layer model
- Each layer is self contained, protocols in one layer don't need to know what the others are doing or how.
- The above point means that a layer can be changed without effecting the other layers
- It also means developers can focus on just one part of the network rules when developing new products, ideas
- It also means that if there is a problem it can be narrowed down to one layer making it easier to fix
- Finally, it creates a universal set of rules which makes companies follow them so all devices will be work with each other
Layer Name | What this layers protocols do | Protocols you will find in this layer |
| Layer 4 - Application Layer | Turn data into websites and other applications. Take "input" from applications and turn it into data | HTTP, HTTPS, FTP, POP3, IMAP, SMTP (basically the table from the protocols page) |
| Layer 3 - Transport Layer | Control the data flow, splits data into packets, checks if packets are sent and received etc | TCP (basically the Transport Layer is the TCPs layer - memory hint>> the T's go together) |
| Layer 2 - Network Layer | Makes the connections between networks, directs data packets, handles traffic, is the layer used by routers | IP |
| Layer 1 - Data Link Layer | Passes data over the physical internet (the cables, or radio waves) | Ethernet |