Typing a URL into a browser feels instant, but behind the scenes a complex sequence of network processes takes place. In IB Computer Science, students are expected to understand this process at a conceptual, step-by-step level, linking together networking, protocols, and servers.
IB examiners reward answers that show logical sequencing, not just a list of buzzwords.
Step 1: URL Is Interpreted by the Browser
When you enter a URL, the browser first:
- Identifies the protocol (usually HTTP or HTTPS)
- Extracts the domain name
- Determines the resource being requested
For example, the browser recognises:
- How the data should be requested
- What type of connection is needed
No data is transferred yet — this is preparation.
Step 2: DNS Lookup
Computers communicate using IP addresses, not domain names.
The browser must:
- Contact a Domain Name System (DNS) server
- Request the IP address associated with the domain name
If the IP address is cached locally, this step is faster.
If not, DNS servers are queried until the correct IP address is found.
This step converts a human-readable name into a machine-usable address.
Step 3: Establishing a Connection
Once the IP address is known, the browser:
- Establishes a connection with the server
- Uses TCP to ensure reliable communication
For secure websites, HTTPS adds:
