What Is a Switch?

What Is a Switch?

A switch is an electromechanical device that connects or disconnects the conducting path in an electrical circuit, interrupting electric current or diverting it from one conductor to another. In computer networking, switches enable devices to communicate with each other, regardless of whether they are in the same room or across the world. Network switches are also responsible for reducing data traffic, which boosts network performance.

A basic switch consists of one or more sets of movable electrical contacts connected to external circuits. The contacts can be in two states: either "closed", meaning the contacts are touching and electricity can pass between them, or "open" — the contacts are separated by an insulating gap and current cannot flow through them at normal voltages. The mechanism actuating the switch causes the transition between these states, which can be permanent (the state in which the switch remains when not being actuated) or momentary. In the case of push-button switches, which are commonly used in home and business settings, the transition occurs when the switch is pushed and then released.

Switches vary in size, speed and connectivity. For example, a small home network switch may only have four Ethernet ports that can support speeds up to 1 Gbps. Alternatively, a large enterprise network switch might have 48 or more ports, including Gigabit Ethernet ports that can support high-speed data transfer rates.

Network switches are most often used to connect computers in a local area network (LAN) together. They do this by forwarding data packets to the correct destination. When a packet of 1s and 0s arrives, the switch examines its MAC address (which is assigned to each networked device) and determines the best port to send it to.

Once the packet reaches its destination, it transmits a signal back to the switch that identifies its location and the MAC address of the intended recipient. The switch then retransmits the packet to that port. This targeted approach prevents unnecessary data traffic from clogging other parts of the network, and it ensures that each device receives a fair share of the available bandwidth.

A network switch also performs error checking and other processing functions. It works at the Data Link Layer of the OSI model, and it can operate in full duplex mode to maximize communication bandwidth. In addition, switches can be configured to filter and prioritize traffic to reduce network latency. For these reasons, network switches are essential to a modern organization.