This is the percentage threshold that, when the node's data buffer usage exceeds it, triggers a buffer-utilization alarm. Since buffers are the node's temporary storage for data passing through, a buffer-utilization alarm firing repeatedly is an early sign the node's overall throughput is nearing its architectural limit, a more systemic warning than a single port's utilization threshold firing. For example, this threshold set to 80% firing repeatedly across the whole node, even when individual ports look fine, could indicate the node overall is approaching its total switching capacity.