The term Internet is a contraction of ‘interconnected networks’; indeed, the Internet is a gigantic global collection of linked networks. The networks that make up the Internet can range from tiny (just two or three connected computers) to massive (thousands of interlinked machines).
An Internet service provider (ISP) is a telecommunications business that delivers Internet-related services such as access to the Internet, domain name registration, website hosting, etc. ISPs enable you to connect to the Internet.
When you use your computer to access the Internet from your home, you most likely connect to an ISP via a modem and a local telephone number or through a dedicated high-speed line. When you connect to your ISP, you become part of their network, which allows you to access the Internet.
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Either way, your home PC or office LAN becomes part of the ISP’s network. The ISP will link to a larger network to become part of that network. That network will be connected to larger networks to create a communications system that spans the globe.
Thus, the Internet is nothing more than a network of networks. These networks connect computers using various technologies, including conventional and high-speed telephone lines, fiber-optic cables, microwave links, wireless technologies, and satellite communications.
Routers
The networks are connected using routers. A router is a specialized computer that directs traffic on the Internet. Routers are necessary as the Internet consists of hundreds of thousands of smaller networks linked together.
When you want to visit a particular website, you type its address into your web browser. The address goes to the nearest router, which decides where that site is on the Internet.
The router also determines the most efficient path through all the networks to reach this destination. This determination is based on the traffic in different parts of the Internet and the available connections.
Higher-level networks
The networks in a particular region may be grouped into a mid-level network. Or they may be linked in a wide-area network (WAN). A WAN covers a larger geographical area than a mid-level network. If the website you are looking for is within the same regional network or WAN, the router will send it directly to its destination.
However, if the website you are looking for is on another part of the Internet, the router will send your request to a network access point (NAP). NAPs connect high-level networks and allow access to Internet backbones.
The Internet backbones are a collection of networks that link extremely powerful supercomputers. The spines comprise fiber optic trunk lines (aka OC for the optical carrier). The fastest OCs can transit 2.488 gigabits per second!
There are many high-capacity backbones worldwide, all interconnected at various NAPs. They enable everyone to communicate freely with everyone else, no matter where they are.
Repeaters
As you can see, the Internet is a veritable jumble of interconnected networks. These networks are linked using a variety of communication technologies, ranging from very slow to ultra-fast. Given how routers decide the most efficient route, your data may circumnavigate the world before reaching its destination.
For example, a Dublin surfer’s request to view a website hosted in London seldom travels directly from Dublin to London; it is likely to be sent via the Americas should this be the fastest route (as measured in milliseconds).
The problem is that the further data has to travel, the more it deteriorates or fades. Repeaters are pieces of hardware that amplify or refresh the stream of data. Boosting the data signals enables the data to circumnavigate the globe yet arrive intact at its final destination.
Linking networks
Various types of equipment are used to connect the various lower-order networks that make up the vastness of the Internet. These include bridges, gateways, and hubs.
Bridges connect LANs. They enable data from one local area network to pass through another LAN en route to yet another LAN.
Gateways are similar to bridges. However, they also translate data from one type of LAN to another. For example, they can translate data from a UNIX system to be intelligible on an Intel-based system.
Hubs link groups of networks so that computers in one network can talk to computers in all the other networks.
Servers and clients
All the computers on the Internet are either servers or clients. Servers are machines that provide services to other devices (hence the name).
There are various kinds of servers, each with specific functions. For example, web servers host websites, while email servers send and receive emails. FTP servers (file transfer protocol servers) upload and download files. One server machine may contain software for several service functions.
Clients are computers that connect to servers. For instance, you can connect to any website from your home or office computer, which is known as a client.
When your client machine connects to a server, it will connect with specific server software running on the server. For example, your client machine will talk to the server’s email software if you are sending an email.
