Computer network

In computer science, computer engineering, and telecommunications, a network is a group of communicating computers and peripherals known as hosts, which communicate data to other hosts via communication protocols, as facilitated by networking hardware. Networks help computers share information and resources with each other.

Within a computer network, hosts are identified by network addresses, which allow networking hardware to locate and identify hosts. Hosts may also have hostnames, memorable labels for the host nodes, which can be mapped to a network address using a hosts file or a name server such as Domain Name Service.

The first computer network was created in 1940 when George Stibitz connected a terminal at Dartmouth to his Complex Number Calculator at Bell Labs in New York. Today, almost all computers are connected to a computer network, such as the global Internet or embedded networks found in many modern electronic devices. Networks support many important applications and services, such as access to the World Wide Web, digital video and audio, application and storage servers, printers, and email and instant messaging applications.

History

Early origins (1940 – 1960s)

In 1940, George Stibitz of Bell Labs connected a teletype at Dartmouth to a Bell Labs computer to show how computers could work together from far away. This was the first time a computer could be used remotely in real time.

In the late 1950s, the U.S. military built a computer network for its Semi-Automatic Ground Environment radar system. They used the Bell 101 modem, the first commercial modem for computers, which let digital data travel over phone lines at 110 bits per second. Ideas about sharing computer time among many users began to grow, leading to early systems that let several people use a computer at the same time.

ARPANET (1969 – 1974)

In the early 1960s, an idea for a worldwide computer network started to take shape. This idea grew into the ARPANET, which began in 1969. The first four computers to join were at universities in California and Utah. Over the next few years, more ideas and technologies were added, such as ways to send information in small blocks and how different networks could work together.

The internet (1974 – present)

In 1974, two researchers published a paper that helped create the idea of the internet. They described how different networks could be linked together. Soon after, they created a set of rules, called the Transmission Control Protocol, that made this possible. New ways to connect computers, like Ethernet, were invented in the 1970s and improved over time to allow much faster speeds.

Commercial usage

In the 1960s, companies began using computer networks for tasks like airline reservations. New technologies made it easier to connect computers over long distances, and by the 1980s, networks were growing around the world.

Hardware

Further information: Data transmission

Networks use different ways to connect devices, such as electrical cable, optical fiber, and free space. These connections work with special software layers that manage how data travels. Common technologies include:

• Ethernet uses wires or fibers to connect devices in small networks.
• Wireless LANs use radio waves or infrared to allow devices to talk without wires.
• Power line communication uses a building's power cabling to send data.

Networks also have special pieces of equipment that help devices talk to each other, like routers and switches. Each device in a network has a unique address so others know where to send information.

Communication

A communication protocol is a set of rules that lets computers share information over a network. These rules can be different in many ways, like whether they need a constant connection or just send pieces of data when needed.

Most networks today send data in small pieces called packets. Each packet has some extra information, like where it's going and how to check if it arrived correctly, along with the actual data. This helps share the network's space fairly among many users. When a packet arrives, the network puts all the pieces back together to get the original message.

The main set of rules used on the Internet is called the Internet protocol suite, or TCP/IP. It handles how data is sent and received across the Internet. There are also special rules for wireless networks, like WiFi, which let devices connect without wires. Other types of networks, like those used for phone calls, have their own rules too.

Routing is how networks decide where to send data. Special devices called routers look at where the data needs to go and choose the best path to get it there. They keep lists of possible paths to help make these decisions.

Architecture

The way computers and devices are connected in a network, called its topology, can affect how well it works. Some setups, like a star network, where all devices connect to one central point, are common in small offices. Others, like mesh networks, connect every device to several others, making them very reliable but more expensive to set up.

Networks can also differ in size. A personal area network might connect devices just a few meters apart, like in a home. Larger networks, such as those in schools or cities, cover much bigger areas. The Internet is the largest network of all, connecting millions of computers worldwide through many different smaller networks.

Services

Network services are special tools that servers on a computer network provide to help users or keep the network running smoothly. Popular examples include the World Wide Web, E-mail, printing, and network file sharing. These services make it easier for people to share information and use the internet.

Some network services, like the Domain Name System (DNS), help us use easy-to-remember names instead of complicated numbers. Others, such as Dynamic Host Configuration Protocol (DHCP), make sure all devices on the network have the right address to communicate. These services follow specific rules, called protocols, to work correctly.

Performance

Bandwidth is how much data can move through a network each second. It can be affected by things like managing how much data can go through at once.

Network delay is the time it takes for data to travel from one place to another in a network. This delay can come from processing the data, waiting in line to be sent, the time it takes to send the data, and the time it takes for the signal to travel through wires or air.

Performance in networks can be measured by how much data gets through, how steady the data flow is, how many errors happen, and how fast the data moves. When too much data tries to go through a network at once, it can get crowded, causing delays or lost data. Modern networks have ways to slow down or stop sending data when this happens to keep things running smoothly.

Security

Computer networks can be used by people with bad intentions to spread harmful software or block access to the network. To protect against this, network security is very important. It includes rules and tools set up by network managers to stop unauthorized people from accessing or harming the network. This helps keep information safe for everyone, whether they are businesses, governments, or individuals.

Network surveillance means watching the data that moves through networks like the Internet. This monitoring can be done secretly and by different groups, including governments and companies. While it helps find and stop illegal activities, some people worry it might limit personal freedoms. End-to-end encryption is a way to keep messages private by encoding them so only the intended recipient can read them. This protects information from being seen or changed by others, such as Internet service providers. Examples include HTTPS for web browsing and PGP for email. However, end-to-end encryption doesn’t protect against all types of attacks, like analyzing who is communicating and when.

Main article: Transport Layer Security