Queueing and packet drops in a router

Several sources share a single output link. Increase the traffic intensity and watch the queue build up, the buffer fill and the router start dropping packets.

0.70
Go to:
8
Arrivals:
Packet size:
Speed:

Buffer occupancy

0 / 8
avg: 0.00

Queueing delay

0.00
average, in transmission times (T = L/R)

Link utilisation

0 %
time spent transmitting

Dropped packets

0.0 %
0 of 0 arrived

Delivered

0
throughput: 0.00 pkt/T
Buffer occupancy over time (last 60 T). Red marks show instants when at least one packet was dropped.
Drop probability vs ρ.
Mean delay (queue + transmission) vs ρ.

The curve is the theoretical M/M/1/N reference (Poisson arrivals, exponential sizes, N = buffer + 1 packet in transmission). The filled dot is the theoretical value for the current ρ; the hollow one is what the simulation has measured since the last parameter change (it needs a few hundred arrivals to settle). Try “Regular” and “Bursty”: same ρ, different behaviour.

Space pause · R reset · ←/→ adjust ρ (with the slider focused). Time unit: T = L/R, the time to transmit one packet.