Random Early Detection (RED) drops packets before queues fill. This avoids TCP synchronization and keeps queues partially empty.
How RED works:
- Monitor average queue depth
- Define min threshold, max threshold, and drop probability
- Below min: no drops
- Between min and max: probability increases linearly
- Above max: tail drop everything
Example: Queue holds packets. Min is , max is , probability is %. At packets, drop probability is %.
RED benefits:
- TCP flows back off at different times
- Queue depth stays moderate
- Link utilization remains stable