In IB Computer Science HL, students are expected to understand how data travels across networks. This is explained using the TCP/IP model, which describes networking as a series of layers, each with a specific role.
Many students confuse the TCP/IP model with the OSI model or memorise layer names without understanding what each layer actually does. In IB exams, examiners reward functional explanations, not rote learning.
What Is the TCP/IP Model?
The TCP/IP model is a layered model that explains:
- How data is prepared for transmission
- How it travels across networks
- How it is received and reconstructed
Each layer:
- Performs a specific task
- Passes data to the next layer
- Works independently but cooperatively
The TCP/IP model consists of four layers.
Application Layer
The Application layer is the layer closest to the user.
It is responsible for:
- Providing network services to applications
- Formatting data for transmission
- Handling user-level protocols
Examples of protocols at this layer include:
- HTTP / HTTPS
- FTP
- SMTP
This layer does not handle transmission details — it focuses on what the data is and how applications use it.
In IB answers, students should link the Application layer to user-facing services.
Transport Layer
The Transport layer controls how data is sent reliably between devices.
Its responsibilities include:
- Breaking data into segments
- Managing data flow
- Error checking
- Ensuring correct delivery
The two most important protocols here are:
- TCP: reliable, ordered delivery
- UDP: faster, but no delivery guarantee
In IB HL, students should understand why TCP and UDP exist and when each is used.
Internet Layer
The Internet layer is responsible for routing data across networks.
Its main tasks include:
- Assigning IP addresses
- Determining the best route for data
- Moving packets between networks
The key protocol here is IP (Internet Protocol).
Routers operate primarily at this layer, making decisions about where packets should go next.
IB students should link this layer to packet routing and addressing.
Network Access Layer
The Network Access layer handles physical transmission of data.
It is responsible for:
- Framing data
- Using MAC addresses
- Transmitting data over physical media
This layer includes:
- Ethernet
- Wi-Fi
- Network Interface Cards
It deals with how data is actually sent, not where it is going.
How Data Moves Through the TCP/IP Model
When sending data:
- The Application layer prepares the data
- The Transport layer segments it
- The Internet layer adds IP addressing
- The Network Access layer transmits it
On receipt, the process happens in reverse.
Why the TCP/IP Model Matters in IB Computer Science
IB HL students may be asked to:
- Describe each layer
- Explain how data moves through layers
- Compare TCP/IP to other models
- Link protocols to layers
Clear explanations earn high marks.
Common Student Mistakes
Students often:
- Mix up layer functions
- Confuse TCP/IP with OSI
- List protocols without explanation
- Skip data flow descriptions
Understanding is more important than memorisation.
Final Thoughts
The TCP/IP model explains how complex network communication is made manageable by dividing it into layers. Each layer has a clear role, from user interaction to physical transmission.
Understanding how these layers work together allows IB Computer Science HL students to explain networking clearly, logically, and accurately — exactly what examiners are looking for.
