This read-only counter tallies frames dropped by the BUS due to timeout, the direct casualty count of the busMaxFrmAge aging timer expiring before a packet could be forwarded. A rising value means the BUS is falling behind on its forwarding queue relative to the very short aging window configured, which under sustained load is a symptom of the BUS itself becoming a bottleneck for the emulated LAN's broadcast traffic. This counter climbing during peak hours on a busy ELAN, even with busMaxFrmAge left at its maximum of 4 seconds, would indicate the BUS needs more forwarding capacity or the ELAN has too many clients relying on flooded traffic.