This configurable threshold (in percentage of shared buffer) determines when high-priority packets start getting dropped according to a configured drop rate on Alcatel-Lucent Subscriber Access Service systems. Once the shared buffer utilization reaches this threshold, high-priority egress packets from a queue are dropped at a predetermined slope rate to prevent complete buffer overflow. An operator sets this threshold to balance quality-of-service guarantees for critical traffic while avoiding buffer exhaustion during traffic spikes.