BIP 31, found in BIP-31, added a simple but important feature to the Bitcoin peer-to-peer protocol: when a node receives a “ping,” it can now send back a matching “pong.” This exchange helps confirm an active connection and ensures messages aren’t just disappearing into the void.

Though small, it standardized a keep-alive mechanism. Before BIP 31, nodes had less direct feedback on network health. Now, by matching ping-pong sequences, nodes quickly detect unresponsive or disconnected peers. This paves the way for more efficient resource management and a better-connected network overall.