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The Internet connects networks rather than providing one direct wire between every pair of hosts. Follow naming, routing and packet delivery as separate processes.
What you'll be able to do
Packet switching divides transferred data into units with addressing and control information. Routers forward packets towards destination networks using routing information. Different packets can take different routes, and the underlying network layer does not by itself guarantee ordered reliable application delivery.
A router forwards between networks, while gateway is a broader term for an interface between networks or systems, sometimes involving protocol translation. A default gateway gives a local host a route beyond its own subnet. State the model rather than assuming every central network device performs the same task.
A domain name is a structured human-readable identifier in a hierarchical naming system. A fully qualified domain name specifies its place in that hierarchy. An IP address identifies an interface/location in the addressing and routing system; it is not the same as a permanent personal identity.
DNS supplies records associated with names, including address records. A resolver can use cached results or query the hierarchy as needed. It does not generally translate an entire URL including path and query into one address: the host name is the relevant part for ordinary name resolution.
A URL can specify a scheme, host, optional port, path and other components. In https://example.org/lessons?id=3, the scheme is https, the host is example.org and the application interprets the path and query after connection and request handling.
Internet registries coordinate allocation and registration of number resources such as address blocks within an organised hierarchy. Domain registration and IP allocation are related infrastructure activities but are not identical services. Avoid claiming a registry stores every page or that DNS contains the entire Internet’s content.
| Item | Example role |
|---|---|
| Domain name | Name resolved through DNS |
| IP address | Network delivery address |
| URL path | Resource requested from the application |
| Router | Forwarding between networks |
Attempt the task before opening its worked response. Record each change of state, explain the rule used, and check the result against the original requirements. Code examples labelled Python 3 use that language’s conventions; pseudocode states its own assumptions.
Common mistakes to avoid
Key takeaways
Test yourself
Answer a few questions, then review anything you missed.
Start with the quiz above to check the key ideas. You can also choose another topic from the practice library.