What is a Computer Network?
A computer network can most easily be described as two or more computers connected to each other. However, this doesn’t fully account for all of the nuances of modern computer networks. The basic idea behind computer networking is becoming more and more blurred as the complexities and capabilities of technology progresses.
The parts of a computer network
At its most basic level, a computer network includes just two computers connected by a wire. This is called a two-host configuration, which requires several different things for the network to function correctly:
- The application layer consists of the programs that generate and use network traffic. For example, these could be anything from a web browser to a Dropbox account. You see these aspects of the network on a daily basis because they create noticeable results.
- The transport layer is a back-end function that turns the data sent and received by the application layer into traffic that another computer can understand. In addition, it tracks which data has already been received so it can resend any data missed.
- The network layer is best described as a postal carrier that picks up and delivers mail to a house. Postal workers know to check for an address and stamp on outgoing mail, while making sure mail is delivered to the correct location (or returned if information can’t be sent). The network layer determines where data must be sent. In the case of a two-host configuration, data is simply sent to the other computer. For a larger network, data will be assigned a destination address similar to a postal letter.
- The link layer consists of the network card in your computer, which can be anything from a wireless card to an Ethernet card to a telephone modem. The link layer turns the transmissions of the network layer into electricity which is then sent through the wires. In a way, the link layer becomes the truck which transports your mail. It doesn’t necessarily know what it’s carrying, the electrical current simply knows to carry the information from one point to another.
How the computer network works
If you were to send an email to the other computer in your two-host configuration, you would first load up your email application. Once the email is written, you would click “send,” which is where the network would come into play. Clicking send takes place at the application layer, in which the email program attempts to open a Simple Mail Transport Protocol (SMTP) connection with the other computer on the network.
The SMTP connection is addressed to the other computer using its IP address. The transport layer then creates a data packet, similar to an envelope for mail, and asks for the other computer to open an SMTP access point for your computer. The network layer figures out where to send the packet requesting the connection. Once identified, the link layer turns the packet into electricity and delivers it to the other computer.
The other computer receives the packet on its own link layer, which it then passes on to the network layer. After identifying which application is listening for an SMTP connection, the network layer turns the data into information the application layer will understand and the email is displayed on the other computer’s email.
Modern complexities of computer networks
In today’s world, you hardly ever see a two-host configuration anymore. Instead, multiple computers are connected together via a router and connected to a modem. Then there are Bluetooth and wireless connections that take place. Each of these variations adds another layer of complexity to how computer networks function, though the core elements listed above remain the same.