Traffic Policing Calculator
Split offered traffic into conforming, exceeding and violating rates for a two-rate three-colour policer.
About Traffic Policing Calculator
A two-rate three-colour policer runs two token buckets. Traffic up to CIR is green, traffic between CIR and PIR is yellow and re-marked for early discard, and anything beyond PIR is dropped immediately. Burst tolerance is simply how long the committed bucket can cover the excess. Unlike a shaper, a policer drops rather than buffers, so an undersized CBS turns normal TCP burstiness into visible packet loss even when the average rate is well under contract.
Formula
Traffic Policing
green = min(offered, CIR); yellow = min(offered − CIR, PIR − CIR); red = offered − PIR; burst tolerance ms = burst size in bits ÷ the matching rate.
- CIR
- Committed rate marked green and always forwarded
- PIR
- Peak rate above which packets are dropped outright
- CBS
- Bucket depth that absorbs short bursts without marking
Worked example
With the default values below, Traffic Policing Calculator returns Traffic Dropped (Red) of 33.33%. Change any input above and every figure here is recalculated in your browser.
Inputs used
- Offered rateaccepts 0–400,000 Mbps
- 120 Mbps
- Committed rate (CIR)accepts 0–400,000 Mbps
- 50 Mbps
- Peak rate (PIR)accepts 0–400,000 Mbps
- 80 Mbps
- Committed burst size (CBS)accepts 1–65,536 KB
- 64 KB
- Excess burst size (EBS)accepts 0–65,536 KB
- 64 KB
Results
- Traffic Dropped (Red)
- 33.33%
- Conforming (Green)
- 50.00 Mbps
- Exceeding (Yellow)
- 30.00 Mbps
- Violating (Red)
- 40.00 Mbps
- Conforming Share
- 41.67%
- CBS Burst Tolerance
- 10.240 ms
- EBS Burst Tolerance
- 6.400 ms
Step by step
- 1Values used
- 2Traffic Policing
- 3Traffic Dropped (Red)= 33.33
- 4Conforming (Green)= 50.00 Mbps
- 5Exceeding (Yellow)= 30.00 Mbps
- 6Violating (Red)= 40.00 Mbps
- 7Conforming Share= 41.67
- 8CBS Burst Tolerance= 10.240 ms
Assumptions and limits
- The result is derived only from the 5 inputs listed above. Anything not among them is not part of the calculation.
- In particular, this calculator does not take inflation, tax, fees or charges or compounding frequency into account.
- Figures are rounded for display to 3 decimal places, so totals built from several rounded parts can differ slightly from the unrounded arithmetic.
How these calculators are built and tested is described on the Methodology page. If a figure looks wrong, please report it.
Frequently Asked Questions
How is Traffic Policing calculated?
green = min(offered, CIR); yellow = min(offered − CIR, PIR − CIR); red = offered − PIR; burst tolerance ms = burst size in bits ÷ the matching rate. A two-rate three-colour policer runs two token buckets. Traffic up to CIR is green, traffic between CIR and PIR is yellow and re-marked for early discard, and anything beyond PIR is dropped immediately. Burst tolerance is simply how long the committed bucket can cover the excess.
Why does Traffic Policing matter?
Unlike a shaper, a policer drops rather than buffers, so an undersized CBS turns normal TCP burstiness into visible packet loss even when the average rate is well under contract.
What values do I need to enter?
This calculator takes 5 inputs: Offered rate, Committed rate (CIR), Peak rate (PIR), Committed burst size (CBS), Excess burst size (EBS). The pre-filled defaults are a realistic starting point — replace them with figures from your own environment for a result you can act on.