Frame switching
Frame switching-
- LAN switches are characterized by the forwarding method that they support, such as a store-and-forward switch, cut-through switch, or fragment-free switch.
- Store-and-forward switches store the entire frame in internal memory and check the frame for errors before forwarding the frame to its destination.
- Store-and-forward switch operation ensures a high level of error-free network traffic, because bad data frames are discarded rather than forwarded across the network
- With cut-through switching, the LAN switch copies into its memory only the destination MAC address, which is located in the first 6 bytes of the frame following the preamble.
- The switch looks up the destination MAC address in its switching table, determines the outgoing interface port, and forwards the frame on to its destination through the designated switch port.
- A cut-through switch reduces delay because the switch begins to forward the frame as soon as it reads the destination MAC address and determines the outgoing switch port
- Fragment-free switching works like cut-through switching with the exception that a switch in fragment-free mode stores the first 64 bytes of the frame before forwarding.
- Fragment-free switching can be viewed as a compromise between store-and-forward switching and cut-through switching.
- The reason fragment-free switching stores only the first 64 bytes of the frame is that most network errors and collisions occur during the first 64 bytes of a frame
