You are designing the QoS policy for a company that is running many TCP-based applications. The company is experiencing tail drops for these applications. The company wants to use a congestion…

Weighted Fair Queuing (WFQ) is a scheduling algorithm that distributes bandwidth fairly among traffic flows, but it does not proactively discard packets to prevent congestion and is not classified as a congestion avoidance technique.

Weighted Random Early Detection (WRED) is a congestion avoidance mechanism that selectively and randomly discards packets as queue depth increases, before the queue reaches maximum capacity. This proactive dropping signals TCP senders to invoke their built-in congestion control algorithms, reducing transmission rates and preventing the sudden loss of all queued packets known as tail drop. WRED supports differentiated drop thresholds per traffic class, making it ideal for environments running multiple TCP-based applications.

First-In First-Out (FIFO) processes packets in arrival order with no prioritization or congestion management, which actually worsens tail drop behavior under sustained congestion.

Low-Latency Queuing (LLQ) is a strict priority queuing mechanism designed to minimize delay and jitter for real-time traffic such as voice and video, not a congestion avoidance technique for TCP applications.