The Internet & World Wide Web (IP & MAC Addresses)

The internet is a global network of connected networks. The World Wide Web is a collection of linked web pages and resources accessed over the internet. Email and file transfer can use the internet without being web pages. HTML describes page structure; it is not a network communication protocol.

URLs and DNS

In https://school.example/library/books.html, https is the protocol, school.example is the domain and /library/books.html identifies the requested resource path.

When a needed address is not cached, a DNS lookup resolves the domain name to an IP address. The browser uses an address returned by DNS to connect to the server and request the resource. DNS is distributed; it does not translate the entire path into an IP address. A resource path need not correspond to a physical file.

IP addresses

An IP address identifies a network interface for routing data. It may be assigned dynamically or configured statically. IPv4 uses 32 bits, commonly shown as four denary groups separated by dots, such as 192.0.2.8. IPv6 uses 128 bits and hexadecimal groups separated by colons, providing a much larger address space. Addresses can change when a device changes networks.

MAC addresses

A NIC commonly has a factory-assigned 48-bit MAC address, shown as six pairs of hexadecimal digits. In the syllabus model, the first part identifies the manufacturer and the remaining part identifies the interface. MAC addresses are used on the local network; routers use IP addresses between networks. Devices may also use software-configured or private/randomised MAC addresses, so 'permanently unchanged on every network' is too strong.

Worked journey

A learner enters a school library URL. DNS supplies the server's IP address, the browser establishes a connection and requests the path, and the server returns resources for rendering. State where the domain, IP address and page path each contribute. Then explain why sending email still uses the internet even if no browser is open.