What are the two key characteristics of store-and-forward switching?

Error checking (via FCS (Frame Check Sequence)/CRC (Cyclic Redundancy Check)) and buffering, which also enables speed mismatch handling between ports.

1. Error Checking:

• The switch receives the entire frame (up to ~9,200 bytes for jumbo frames)
• It calculates the Frame Check Sequence (FCS) using a CRC algorithm
• Compares its calculated CRC with the FCS field at the end of the frame
• If they don't match → the frame is discarded (bad frame)
• This prevents corrupt frames from wasting bandwidth on the network

2. Buffering:

• The ingress port buffers (stores) the frame while checking the FCS
• This buffering also allows the switch to handle speed mismatches — e.g., a frame arriving on a 1 Gbps port can be forwarded out a 100 Mbps port
• The switch queues frames in memory and transmits them at the egress port's speed

Store-and-forward is Cisco's preferred method because the reliability of error checking outweighs the small latency cost for most use cases.

Go deeper:

• Frame check sequence (Wikipedia) — the FCS/CRC store-and-forward recomputes to discard corrupt frames.
• Network congestion (Wikipedia) — the buffering/queueing that lets store-and-forward bridge speed mismatches.