MikroTik burst calculator
Enter max-limit, burst-limit, burst-threshold and burst-time and see exactly how long a client bursts from idle, how much data that is, and the queue line to paste.
Runs in your browser; nothing you type leaves your device
Models RouterOS burst for one client with unlimited demand, measured in steps of burst-time/16 as RouterOS does. Real traffic is burstier, and parent queues can limit a client below these numbers. MikroTik and RouterOS are trademarks of SIA Mikrotīkls. This tool is independent and not affiliated with or endorsed by MikroTik.
How to calculate MikroTik burst settings
- Enter max-limit, burst-limit, burst-threshold and burst-time for upload and download. Rates take k, M or G, such as 20M.
- Read how long the burst lasts from idle and look at the chart, which shows the allowed rate and the average RouterOS compares with the threshold.
- Optionally enter the burst length you want to get the threshold that produces it, then copy the simple queue or PPP rate-limit line.
Burst in RouterOS queues, step by step
Burst lets a client go faster than its max-limit for a short time, so web pages and small downloads feel quick while long transfers still settle at the plan's rate. Four settings control it, each given as upload/download in a simple queue: max-limit, the normal ceiling; burst-limit, the higher ceiling while bursting; burst-threshold, the average rate at which bursting stops; and burst-time, the window over which that average is measured.
RouterOS splits burst-time into 16 slots. After each slot it averages the client's rate over the last 16 slots and compares it with the threshold: below it, the client may use burst-limit; at or above it, only max-limit. A client coming from idle starts with an average of zero, sends at burst-limit, and the average climbs until it crosses the threshold. With 8 s burst-time, a 40M burst-limit and a 16M threshold, the average reaches the threshold after 3.2 s, and the next check, at 3.5 s, ends the burst; the client has moved about 17.5 MB by then. Then the average stays above the threshold as long as the client keeps transferring at max-limit, so the next burst needs a pause.
Choosing values
- Set burst-limit to the speed you want short transfers to feel like, often 1.5 to 2 times max-limit.
- Keep burst-threshold below max-limit, typically 60 to 80% of it, and tune burst-time to get the burst length you want.
- Turn FastTrack off, or exclude queued clients from it: fasttracked packets skip simple queues entirely. Generate the queues with the simple queue generator or as PPP profiles with the PPPoE server generator.
Questions
How does burst work on MikroTik?
Every burst-time/16, RouterOS works out the client's average rate over the last burst-time. While that average is below burst-threshold, the queue lets the client send up to burst-limit; once the average reaches the threshold, the client drops to max-limit. A client that has been idle has an average of zero, so a new download starts at burst-limit and falls back to max-limit after a few seconds.
How long does the burst last?
Starting from idle with a client that takes everything offered, the burst lasts about burst-threshold × burst-time ÷ burst-limit. With burst-limit 40M, threshold 16M and burst-time 8s that is 16 × 8 ÷ 40 = 3.2 seconds. The average is only rechecked every burst-time/16 (half a second here), so the burst really ends at the first check after that point, at 3.5 seconds; the calculator steps through those checks and shows both figures.
Why should burst-threshold be below max-limit?
If the threshold is above max-limit, a client downloading at max-limit has an average below the threshold, so the burst switches back on, the average climbs, the burst switches off, and the client keeps oscillating. With the threshold below max-limit, a client that keeps downloading stays at max-limit and only bursts again after a pause.
What is the rate-limit line for?
PPP profiles, PPP secrets and RADIUS (the Mikrotik-Rate-Limit attribute) take the same limits as one string: max-limit, burst-limit, burst-threshold and burst-time, each as rx/tx from the router's side, which is upload/download for the client. RouterOS builds a dynamic simple queue from it when the client connects.
Is limit-at part of burst?
No. limit-at is the rate the queue guarantees when the parent is congested; burst only changes how high above max-limit a client may go for a while. Keep limit-at at or below max-limit.
Is anything sent to a server?
No. The simulation and the chart are calculated in your browser.