Deficit Round Robin (DRR)

💡 The Core Idea

A scheduling algorithm that provides fair bandwidth allocation and handles variable packet sizes with $O(1)$ complexity, avoiding the high cost of bit-by-bit fair queuing.

🧠 Mechanism

Each flow is assigned:

1. Quantum ($Q_i$): The bandwidth share per round (e.g., 500 bits).
2. Deficit Counter ($D_i$): Tracks unused credit.

The Algorithm

• In each round, add $Q_i$ to $D_i$.
• Send packets from the flow as long as $\text{Packet Size} \le D_i$.
• Decrement $D_i$ by the size of sent packets.
• If the queue is empty, reset $D_i$ to 0.

🔗 Connections

• Source: Source - Packet Classification and QoS