IntermediateTopic 66 of 104Software & Computing
OSI and TCP/IP models
Layered models that structure protocols.
In depth
OSI has seven layers (physical, data link, network, transport, session, presentation, application); the practical TCP/IP model has four (link, internet, transport, application). Each layer encapsulates data from the above with headers and offers services to it. Layering enables interoperability.
Key points
- Encapsulation
- Ethernet, IP, TCP, HTTP
- Debugging by layer
ExampleA web request passes down through TCP, IP and Ethernet layers.
What is OSI and TCP/IP models?
Layered models that structure protocols.
Why is it important to understand OSI and TCP/IP models?
Layered models separate the functions of networking, so each protocol can change without disturbing the others.
What are the seven OSI layers?
Physical, data link, network, transport, session, presentation and application.
How does TCP/IP differ from OSI?
TCP/IP uses four layers and is the practical model of the internet, while OSI is a reference model with seven layers.
How is OSI and TCP/IP models used in practice?
Typical applications include explaining where a fault lies when a web request fails, choosing which layer handles encryption in a design and comparing how ethernet and Wi-Fi fit under the same network layer.
What should I learn before OSI and TCP/IP models?
Study "Computer networks" first (topic 65 of 104 in Software & Computing). It covers the groundwork this topic builds on.
What are the key points of OSI and TCP/IP models?
Encapsulation. Ethernet, IP, TCP, HTTP. Debugging by layer.
Can you give an example of OSI and TCP/IP models?
A web request passes down through TCP, IP and Ethernet layers.
What comes after OSI and TCP/IP models?
The next topic is "IP addressing and routing", which builds directly on this one.
How difficult is OSI and TCP/IP models?
It is classed as Intermediate in Software & Computing (topic 66 of 104). It is an intermediate topic. Work through the beginner topics in Software & Computing first.