How does switching work

To allow communication between billions of computer devices, intermediate network devices are needed. As we know from the How does Router work post , routers, like crossroads and road signs, properly direct packets from the source to the destination. They look into the IP packet header searching for the destination IP address Source and destination IP are included in the packet header and based on local routing table, route the packet to the next hop towards the destination.

As an IP packet has info for router, a frame has info for switch. What is the purpose of a frame? We have nowadays two most common types of network access:. Frame is a portion of information that allows for packet to traverse particular medium from one device interface to another.

Ethernet, as an example, describes many technical parameters of how devices can access the network, how cable connectors should look, what speeds the transmission can achieve and finally how the bits and addressing are organized. So layer 2 is strictly connected with type of medium or interface of device. The Layer 2 is where the switch operates marked in red.

Every IP device produces packets and they are forwarded across the network regardless of network access type. Every access type uses its own structure to forward the data in its environment. Ethernet uses structure called Ethernet Frame. To transport IP packet through the Ethernet environment, Ethernet facing device adds extra bits to the front and back of the IP packet making the frame.

This bit-adding proccess is called encapsulation. The frame header contains inter alia source and destination MAC addresses. The source MAC address is the physical address of the sending device, the destination MAC address is the Ethernet physical interface address of destination device within the same Ethernet segment. You can ask: If there is computer to computer direct Ethernet connection why I need the ethernet switch?

Right, but what if you need to connect third device to the group of devices ethernet segment? Then you need a communication device with a particular logic. And this is what switch is intended for. Now, we need to have some devices that allow us to connect high amount of users and wired devices together. This is something that routers are not intended for. Because routers in most situations have limited number of ports, operate with more advanced features and they are more expensive.

Not possible, not enough ports! Switch is the required medium for such requirement. Switches are considered the best network devices to wire connect high number of ethernet devices. If we have computers connected to our switch we can concentrate on how does switch really work.

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Computer Hardware. Of course, there are cases where switching functionality is built into a router hardware, and the router performs as the switch as well. The easiest case here is to think of your home wireless router.

It routes to a broadband connection through its WAN port, but it usually also has additional ethernet ports that you can use to connect an ethernet cable for a computer, television, printer or even a gaming console. While other devices on the network, such as other notebooks and phones, connect through the Wi-Fi router, it still offers switching functions through the LAN. So the router, in effect, is also a switch. And you can even connect a separate switch to the router to provide both internet and LAN access for additional devices.

In a small office or home office, a four- or eight-port switch usually suffices, but for larger deployments you generally see switches up to ports.

The form factor of a smaller switch is an appliance that you can fit on a desktop, but switches are also rack-mountable for placement in a wiring closet or data center or server farm. Sizes of rack-mountable switches range from 1U to 4U, but larger ones area also available.

Which speed to choose depends on the throughput needed for the tasks being supported. Unmanaged switches are the most basic, offering fixed configuration. They are generally plug-and-play, which means they have few if any options for the user to choose from.

They may have default settings for features such as quality of service, but they cannot be changed. The upside is that unmanaged switches are relatively inexpensive, but their lack of features make them unsuitable for most enterprise uses.

Managed switches offer more functionality and features for IT professionals and are the type most likely seen in business or enterprise settings. Managed switches have command-line interfaces CLI to configure them. They support simple network management protocol SNMP agents that provide information that can be used to troubleshoot network problems. The security is also better, protecting all types of traffic that they handle. Smart or intelligent switches are managed switches that have some features beyond what an unmanaged switch offers, but fewer than a managed switch.

So they are more sophisticated than unmanaged switches, but they are also less expensive than a fully manageable switch. Other options, such as VLANs, may not have as many features as those supported by fully managed switches.