Congestion Calculator
Estimate network congestion level from link utilization and traffic load.
Inputs
Router buffer capacity expressed as max queuing delay
Link Utilization
80.00%
Congestion Level
High — approaching saturation
Excess Traffic (above capacity)
0.00Mbps
Estimated Packet Loss
0.00%
Step by step
Link utilization
800 / 1000 * 100
= 80%
Excess traffic
max(0, 800 - 1000)
= 0 Mbps
Estimated packet loss
0 (under capacity)
= 0%
How it works
Network congestion occurs when offered traffic load approaches or exceeds link capacity. As utilization rises above ~70%, queuing delays increase nonlinearly. When load exceeds capacity, excess packets are dropped (tail-drop) or marked (ECN), causing retransmissions that further increase effective load.
Formula
Link utilization
utilization% = offered_load / link_capacity * 100
- lambda
- Offered traffic load
- C
- Link capacity
Frequently Asked Questions
Why does congestion increase nonlinearly near capacity?
Queuing theory (M/M/1 model) shows that as utilization approaches 100%, average queue length and delay grow toward infinity — small increases in load cause disproportionately large increases in delay, which is why keeping utilization below 70-80% is a common engineering target.
How does TCP respond to congestion?
TCP congestion control algorithms (Reno, CUBIC, BBR) reduce sending rate when packet loss or increased delay signals congestion, then gradually probe for available capacity — this feedback loop is what prevents network collapse but also causes throughput fluctuations.