How LAN Switches Work

By: Jeff Tyson

Switch Configurations

LAN switches vary in their physical design. Currently, there are three popular configurations in use:

  • Shared memory - This type of switch stores all incoming packets in a common memory buffer shared by all the switch ports (input/output connections), then sends them out via the correct port for the destination node.
  • Matrix - This type of switch has an internal grid with the input ports and the output ports crossing each other. When a packet is detected on an input port, the MAC address is compared to the lookup table to find the appropriate output port. The switch then makes a connection on the grid where these two ports intersect.
  • Bus architecture - Instead of a grid, an internal transmission path (common bus) is shared by all of the ports using TDMA. A switch based on this configuration has a dedicated memory buffer for each port, as well as an ASIC to control the internal bus access.