When data is sent across a network, it must be transferred in a way that matches the needs of the application. In IB Computer Science, this is explained using two transport-layer protocols: TCP and UDP.
Students are expected to understand how TCP and UDP differ, why both exist, and when each one should be used. Simply stating that one is “reliable” and the other is “faster” is not enough for high marks.
Where TCP and UDP Fit in Networking
TCP and UDP both operate at the Transport layer of the TCP/IP model.
Their role is to:
- Control how data is sent between devices
- Manage communication between applications
- Decide how reliability and speed are handled
They sit above the Internet layer (IP) and below the Application layer.
What Is TCP?
Transmission Control Protocol (TCP) is a reliable, connection-based protocol.
Key features of TCP include:
- Establishes a connection before data is sent
- Ensures data arrives in the correct order
- Detects and retransmits lost data
- Uses acknowledgements to confirm delivery
Because of this, TCP prioritises accuracy and reliability over speed.
Real Examples of TCP
TCP is used when:
- Data must arrive completely and correctly
- Errors cannot be tolerated
Common uses include:
- Web browsing (HTTP/HTTPS)
