Benefits of Using Switches
A collision domain is a set of devices whose frames could collide. All devices on a 10BASE2, 10BASE5, or any network using a hub risk collisions between the frames that they send, so all devices on one of these types of Ethernet networks are in the same collision domain and use CSMA/CD to detect and resolve collisions.
LAN switches significantly reduce, or even eliminate, the number of collisions on a LAN. Unlike hubs, switches do not create a single shared bus. Instead, switches do the following:
- They interpret the bits in the received frame so that they can typically send the frame out the one required port, rather than all other ports.
- If a switch needs to forward multiple frames out the same port, the switch buffers the frames in memory, sending one at a time, thereby avoiding collisions.
In addition, switches with only one device cabled to each port of the switch allow the use of full-duplex operation. Full-duplex means that the NIC can send and receive concurrently, effectively doubling the bandwidth of a 100Mbps link to 200Mbps—100Mbps for sending and 100Mbps for receiving.
These seemingly simple switch features provide significant performance improvements as compared with using hubs. In particular:
- If only one device is cabled to each port of a switch, no collisions can occur.
- Devices connected to one switch port do not share their bandwidth with devices connected to another switch port. Each has its own separate bandwidth, meaning that a switch with 100Mbps ports has 100Mbps of bandwidth per port.