How Computer Networks Work

Bundle of fibre optics used to send data, a representation of computer networks
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During the past 20 years, the planet has gradually been covered by computer networks of various kinds. Understanding the basics of how these networks work helps us learn how to better use them and also increases our awareness of the changing world around us. This installment of our series on How Computer Networks Work examines devices - hardware systems that connect to the network and communicate with each other.

What Makes a Network Device

Not every computer, handheld gadget or other piece of equipment is capable of joining a network. A network device possesses special communications hardware to make the necessary physical connections to other devices. Most modern network devices have communication electronics integrated onto their circuit boards.

Some PCs, older Xbox game consoles, and other older devices do not have built-in communications hardware but can be set up as network devices by plugging in separate network adapters in the form of USB peripherals. Very old desktop PCs required physically inserting separate large add-in cards into the system motherboard, originating the term Network Interface Card (NIC).

Newer generations of consumer appliances and gadgets are being built as network devices when older generations were not. For example, traditional home thermostats did not contain any communications hardware, nor could they be joined to a home network via peripherals.

Finally, some kinds of equipment do not support networking at all. Consumer devices that neither have built-in network hardware nor accept peripherals include older Apple iPods, many televisions, and toaster ovens.

Device Roles on Computer Networks

Devices on computer networks function in different roles.

The two most common roles are clients and servers. Examples of network clients include PCs, phones and tablets, and network printers. Clients generally make a request and consume data stored in network servers, devices generally designed with large amounts of memory and/or disk storage and high-performance processors to better support clients. Examples of network servers includeWeb servers and game servers. Networks naturally tend to support many more clients than servers. Both clients and servers are sometimes called network nodes.

Network devices may also be capable of functioning as both clients and servers. In a peer to peer networking, for example, pairs of devices share files or other data with each other, one acting as a server hosting some data while simultaneously working as a client to request different data from other peer devices.

Special Purpose Network Devices

Client and server nodes can be added or removed from a network without blocking the communication of other devices that still remain. Certain other types of network hardware, however, exist for the sole purpose of enabling a network to run:

  • A network hub enables any node connected to it to directly send data to others
  • Network switches perform the same function as hubs but include additional hardware logic that opens up multiple communication paths allowing multiple connected nodes to send data directly to each other instead of to all others on the network as with hubs
  • Network routers further expand the capabilities of network switches by supporting connections outward from itself to other networks, joining them together without disrupting the functionality of each one individually.
  • A network repeater receives the physical signals sent across a network connection and amplifies their strength (such as electrical or radio power) to enable the signal to travel longer distances
  • A less common type of device nowadays, the network bridge device connects two different kinds of physical network links together that otherwise would be incompatible, such as bridges that enable wireless devices to join a wired network. (Modern bridge technology is often physically integrated into other types of devices.)