Random Early Detection (RED)
Router notifies source before congestion happens
- just drop the packet (TCP will timeout and adjust its window)
- could make explicit by marking the packet
- rather than wait for queue to become full, drop each arriving packet with some drop probability whenever the average queue length exceeds some drop level
RED details (normal, congestion avoidance, congestion control)
- compute average queue length as weighted average of queue lengths each time a packet arrives
- If average is less than minimum threshold, enqueue the packet
- If average exceeds maximum threshold, drop arriving packet
- Otherwise, drop arriving packet with probability P