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| Switching in IT and computer networking is the transfer of data packets, or blocks of data, through a network switch. Switches transfer data from source ports on devices such as computers to destination ports on devices such as routers. |
What is a switch?
A switch is a hardware component in network infrastructure that performs the switching process. The switch connects network devices, such as computers and servers, to one another.
A switch enables multiple devices to share a network while preventing each device's traffic from interfering with other devices' traffic. The switch acts as a traffic cop at a busy intersection. When a data packet arrives at one of its ports, the switch determines which direction the packet is headed. It then forwards the packet through the correct port for its destination.
Some data packets might come to the switch from devices, like computers or voice-over-IP (VoIP) phones, that are attached directly to it. Other data packets might come to the switch from indirectly connected devices, through a network element such as a hub or router.
The switch knows which of the network's devices are connected to it, and it can transfer data packets between those devices directly. In other cases, data packets may be going to more-distant destinations, on other networks. A switch in such a scenario forwards the packets to a router, which then forwards them to their destinations on the network.
How is a switch different from a hub?
Before there were switches, there were network hubs. Hubs enable many devices to plug into a network through a single shared port on a router. The disadvantage of hubs is that when a hub receives a packet, it sends copies of the packet to every other device connected to it. This can cause problems with traffic congestion and data security.
Switches solve this problem by keeping tables of the MAC addresses of all devices sending packets to them and forwarding packets only to their destinations, instead of flooding all connected devices with the packets.
How is a switch different from a router?
A switch connects devices within a LAN (local-area network) by using MAC addresses to identify where to send data packets. A router connects LANs to other area networks or to the internet. A router uses IP addresses to route data packets.
How has switching technology evolved?
Switches are still at the core of network infrastructure, but today's advanced switches can do much more than just connect devices in a network or IT environment. Most important, advanced switches can act as both switches and routers.
Modern Ethernet switches incorporate features and functions that eliminate the need for some types of additional hardware. For example, switches now include security capabilities that were once handled by dedicated firewalls.
Also, multigigabit switches can provide variable speeds to match the throughput needs of wireless access points, which provide Wi-Fi access to devices such as laptops and mobile phones. And advancements in Power over Ethernet (PoE) switches can supply devices over copper Ethernet cable with up to 90 watts of power per switch port.
Some switches now incorporate machine learning, so they can act as network sensors, collecting data about the network to help network engineers make informed decisions. Modern switches are also programmable and can include network monitoring applications and network analytics tools.
Expect advancements in switching to continue to evolve, with switches taking on even more tasks and further increasing efficiency of data transmission across IT networks.
Types of Switches
Unmanaged switches
Unmanaged switches have basic connectivity and limited capacity. They are essentially "plug and play" devices that can be set up to operate without being configured in some way. Unmanaged switches are typically used in small networks that don't have critical requirements for security or availability
Managed switches.
Networking experts need to configure managed switches, which are designed for use in large, complex networks that demand reliability and security. These switches offer more capacity than unmanaged switches and provide more operational flexibility and control. Managed switches also can provide network analytics, simplify management, and deploy software updates through automation.
Fixed switches
Fixed switches have fixed numbers of downlink ports—8, 12, 24, or 48. Each downlink port connects a device to a fixed switch and can provide power to the devices. Uplink ports are often modular, with interchangeable network modules that allow for upgrades to the overall throughput of the switch. Ports can be connected with fiber cables for higher throughput or copper cables for PoE.
Fixed switches are also stackable. They are often stacked in groups, each of which acts as a single switch.
When more than 144 ports are needed, modular switches (described below) can be a good option.
Modular switches
Modular switches are customizable and thus provide more flexibility than fixed switches. These switches often have 4, 7, or 10 slots that hold line cards with various numbers and types of ports. Networking experts can configure the switches to support an organization's networking needs.
For example, line cards for access ports, routing, security, and other features can be removed from the slots and replaced with different versions. Also, fan trays and power-supply placement may offer flexibility. These modular capabilities enable future expansion and lifecycle longevity.