The word 'Internet' is a shortened form of 'inter' and 'network', meaning interconnected networks. It is best thought of as a network of networks – the biggest WAN of all.

Schools, organizations and homes all have networks that are part of the Internet. Its reach is global: all countries have multiple cables, fiber-optic links and satellites connecting them to other countries. These links, together with others within each country, form the Internet backbone (spina dorsale) – the connections that link all networks together.

How the Internet Works

Internet Service Providers (ISP)

Your computer or network connects to the Internet through an Internet Service Provider (ISP) – an organization that provides Internet connections. The most common connection method is through telephone lines.

The Internet uses the TCP/IP protocol stack (insieme dei protocolli) to allow communication between all the different networks.

The Internet Protocol (IP)

The Internet Protocol (IP) is the part of the stack that handles addressing – it assigns a unique address to each device or network connected to the Internet, so that data can be sent to and from it.

There are currently two versions in use:

Routers

Networks that are part of the Internet are linked together using routers – pieces of networking hardware that forward (inoltrano) packets between networks.

How a router works:

1. It receives a packet;
2. It reads the destination address from the packet header;
3. It consults its routing table – a list of rules stating where to send packets for different destinations;
4. It forwards the packet to the next router;