This counts data chunks that had to be retransmitted within this specific association, giving a per-association retransmission rate that's far more actionable than a device-wide aggregate when trying to isolate which particular peer relationship is experiencing loss. Comparing this against the association's total sent chunks yields a retransmission percentage that's a standard proxy for path quality to that specific peer. An association showing a retransmission rate well above its siblings to different peers on the same device points at a problem specific to that one path, such as congestion or a lossy last-mile link to that peer.