Manual:Queues - Burst

Theory

Burst is a feature that allows to satisfy queue requirement for additional bandwidth even if required rate is bigger that MIR (max-limit) for a short period of time.

Burst can occur only if average-rate of the queue for the last burst-time seconds is smaller that burst-threshold. Burst must stop if average-rate of the queue for the last burst-time seconds is bigger or equal to burst-threshold

Burst mechanism is simple - if burst is allowed max-limit value is replaced by burst-limit value. When burst is disallowed max-limit value remains unchanged.

1. burst-limit (NUMBER) : maximal upload/download data rate which can be reached while the burst is allowed
2. burst-time (TIME) : period of time, in seconds, over which the average data rate is calculated. (This is NOT the time of actual burst)
3. burst-threshold (NUMBER) : basically this is value of burst on/off switch.
4. average-rate (read-only) : Every 1/16 part of the burst-time, the router calculates the average data rate of each class over the last burst-time seconds.
5. actual-rate (read-only) : actual traffic transfer rate of the queue

Values:

limit-at=1M

max-limit=2M

burst-threshold=1500k

burst-limit=4M

Client will try to download two 4MB (32Mb) files, first download will start at zero seconds, second download will start at 17th second. Traffic was unused for last minute.

Example Burst-time=16s

Average rate is calculated every 1/16 of burst time, so in this case 1s

Zero second - average-rate=(0+0+0+0+0+0+0+0+0+0+0+0+0+0+0+0)/16=0Kbps, average-rate < burst-threshold -> Burst is allowed -> Actual-rate=4Mbps

1,0 second - average-rate=(0+0+0+0+0+0+0+0+0+0+0+0+0+0+0+4)/16=250Kbps, average-rate < burst-threshold -> Burst is allowed -> Actual-rate=4Mbps

2,0 second - average-rate=(0+0+0+0+0+0+0+0+0+0+0+0+0+0+4+4)/16=500Kbps, average-rate < burst-threshold -> Burst is allowed -> Actual-rate=4Mbps

3,0 second - average-rate=(0+0+0+0+0+0+0+0+0+0+0+0+0+4+4+4)/16=750Kbps, average-rate < burst-threshold -> Burst is allowed -> Actual-rate=4Mbps

4,0 second - average-rate=(0+0+0+0+0+0+0+0+0+0+0+0+4+4+4+4)/16=1000Kbps, average-rate < burst-threshold -> Burst is allowed -> Actual-rate=4Mbps

5,0 second - average-rate=(0+0+0+0+0+0+0+0+0+0+0+4+4+4+4+4)/16=1250Kbps, average-rate < burst-threshold -> Burst is allowed -> Actual-rate=4Mbps

6,0 second - average-rate=(0+0+0+0+0+0+0+0+0+0+4+4+4+4+4+4)/16=1500Kbps, average-rate = burst-threshold -> Burst not allowed -> Actual-rate=2Mbps

7,0 second - average-rate=(0+0+0+0+0+0+0+0+0+4+4+4+4+4+4+2)/16=1625Kbps, average-rate > burst-threshold -> Burst not allowed -> Actual-rate=2Mbps

8,0 second - average-rate=(0+0+0+0+0+0+0+0+4+4+4+4+4+4+2+2)/16=1750Kbps, average-rate > burst-threshold -> Burst not allowed -> Actual-rate=2Mbps

9,0 second - average-rate=(0+0+0+0+0+0+0+4+4+4+4+4+4+2+2+2)/16=1750Kbps, average-rate > burst-threshold -> Burst not allowed -> Actual-rate=2Mbps

10,0 second - average-rate=(0+0+0+0+0+0+4+4+4+4+4+4+2+2+2+2)/16=1875Kbps, average-rate > burst-threshold -> Burst not allowed -> Actual-rate=0Mbps

11,0 second - average-rate=(0+0+0+0+0+4+4+4+4+4+4+2+2+2+2+0)/16=1875Kbps, average-rate > burst-threshold -> Burst not allowed -> Actual-rate=0Mbps

12,0 second - average-rate=(0+0+0+0+4+4+4+4+4+4+2+2+2+2+0+0)/16=1875Kbps, average-rate > burst-threshold -> Burst not allowed -> Actual-rate=0Mbps

13,0 second - average-rate=(0+0+0+4+4+4+4+4+4+2+2+2+2+0+0+0)/16=1875Kbps, average-rate > burst-threshold -> Burst not allowed -> Actual-rate=0Mbps

14,0 second - average-rate=(0+0+4+4+4+4+4+4+2+2+2+2+0+0+0+0)/16=1875Kbps, average-rate > burst-threshold -> Burst not allowed -> Actual-rate=0Mbps

15,0 second - average-rate=(0+4+4+4+4+4+4+2+2+2+2+0+0+0+0+0)/16=1875Kbps, average-rate > burst-threshold -> Burst not allowed -> Actual-rate=0Mbps

16,0 second - average-rate=(4+4+4+4+4+4+2+2+2+2+0+0+0+0+0+0)/16=1875Kbps, average-rate > burst-threshold -> Burst not allowed -> Actual-rate=0Mbps

17,0 second - average-rate=(4+4+4+4+4+2+2+2+2+0+0+0+0+0+0+0)/16=1625Kbps, average-rate > burst-threshold -> Burst not allowed -> Actual-rate=2Mbps

18,0 second - average-rate=(4+4+4+4+2+2+2+2+0+0+0+0+0+0+0+2)/16=1500Kbps, average-rate = burst-threshold -> Burst not allowed -> Actual-rate=2Mbps

19,0 second - average-rate=(4+4+4+2+2+2+2+0+0+0+0+0+0+0+2+2)/16=1375Kbps, average-rate < burst-threshold -> Burst is allowed -> Actual-rate=4Mbps

20,0 second - average-rate=(4+4+2+2+2+2+0+0+0+0+0+0+0+2+2+4)/16=1375Kbps, average-rate < burst-threshold -> Burst is allowed -> Actual-rate=4Mbps

21,0 second - average-rate=(4+2+2+2+2+0+0+0+0+0+0+0+2+2+4+4)/16=1375Kbps, average-rate < burst-threshold -> Burst is allowed -> Actual-rate=4Mbps

22,0 second - average-rate=(2+2+2+2+0+0+0+0+0+0+0+2+2+4+4+4)/16=1375Kbps, average-rate < burst-threshold -> Burst is allowed -> Actual-rate=4Mbps

23,0 second - average-rate=(2+2+2+0+0+0+0+0+0+0+2+2+4+4+4+4)/16=1500Kbps, average-rate = burst-threshold -> Burst not allowed -> Actual-rate=2Mbps

24,0 second - average-rate=(2+2+0+0+0+0+0+0+0+2+2+4+4+4+4+2)/16=1500Kbps, average-rate = burst-threshold -> Burst not allowed -> Actual-rate=2Mbps

25,0 second - average-rate=(2+0+0+0+0+0+0+0+2+2+4+4+4+4+2+2)/16=1500Kbps, average-rate = burst-threshold -> Burst not allowed -> Actual-rate=2Mbps

26,0 second - average-rate=(0+0+0+0+0+0+0+2+2+4+4+4+4+2+2+2)/16=1500Kbps, average-rate = burst-threshold -> Burst not allowed -> Actual-rate=2Mbps

27,0 second - average-rate=(0+0+0+0+0+0+2+2+4+4+4+4+2+2+2+2)/16=1625Kbps, average-rate > burst-threshold -> Burst not allowed -> Actual-rate=2Mbps

28,0 second - average-rate=(0+0+0+0+0+2+2+4+4+4+4+2+2+2+2+2)/16=1750Kbps, average-rate > burst-threshold -> Burst not allowed -> Actual-rate=2Mbps

29,0 second - average-rate=(0+0+0+0+2+2+4+4+4+4+2+2+2+2+2+2)/16=1875Kbps, average-rate > burst-threshold -> Burst not allowed -> Actual-rate=0Mbps

30,0 second - average-rate=(0+0+0+2+2+4+4+4+4+2+2+2+2+2+2+0)/16=1875Kbps, average-rate > burst-threshold -> Burst not allowed -> Actual-rate=0Mbps

31,0 second - average-rate=(0+0+2+2+4+4+4+4+2+2+2+2+2+2+0+0)/16=1875Kbps, average-rate > burst-threshold -> Burst not allowed -> Actual-rate=0Mbps

Example Burst-time=8s

Average rate is calculated every 1/16 of burst time, so in this case 0,5s

Zero second - average-rate=(0+0+0+0+0+0+0+0+0+0+0+0+0+0+0+0)/8=0Kbps, average-rate < burst-threshold -> Burst is allowed -> Actual-rate=4Mbps (2Mb per 0,5sek)

0,5 second - average-rate=(0+0+0+0+0+0+0+0+0+0+0+0+0+0+0+2)/8=250Kbps, average-rate < burst-threshold -> Burst is allowed -> Actual-rate=4Mbps (2Mb per 0,5sek)

1,0 second - average-rate=(0+0+0+0+0+0+0+0+0+0+0+0+0+0+2+2)/8=500Kbps, average-rate < burst-threshold -> Burst is allowed -> Actual-rate=4Mbps (2Mb per 0,5sek)

1,5 second - average-rate=(0+0+0+0+0+0+0+0+0+0+0+0+0+2+2+2)/8=750Kbps, average-rate < burst-threshold -> Burst is allowed -> Actual-rate=4Mbps (2Mb per 0,5sek)

2,0 second - average-rate=(0+0+0+0+0+0+0+0+0+0+0+0+2+2+2+2)/8=1000Kbps, average-rate < burst-threshold -> Burst is allowed -> Actual-rate=4Mbps (2Mb per 0,5sek)

2,5 second - average-rate=(0+0+0+0+0+0+0+0+0+0+0+2+2+2+2+2)/8=1250Kbps, average-rate < burst-threshold -> Burst is allowed -> Actual-rate=4Mbps (2Mb per 0,5sek)

3,0 second - average-rate=(0+0+0+0+0+0+0+0+0+0+2+2+2+2+2+2)/8=1500Kbps, average-rate = burst-threshold -> Burst not allowed -> Actual-rate=2Mbps (1Mb per 0,5sek)

3,5 second - average-rate=(0+0+0+0+0+0+0+0+0+2+2+2+2+2+2+1)/8=1625Kbps, average-rate > burst-threshold -> Burst not allowed -> Actual-rate=2Mbps (1Mb per 0,5sek)

4,0 second - average-rate=(0+0+0+0+0+0+0+0+2+2+2+2+2+2+1+1)/8=1750Kbps, average-rate > burst-threshold -> Burst not allowed -> Actual-rate=2Mbps (1Mb per 0,5sek)

4,5 second - average-rate=(0+0+0+0+0+0+0+2+2+2+2+2+2+1+1+1)/8=1875Kbps, average-rate > burst-threshold -> Burst not allowed -> Actual-rate=2Mbps (1Mb per 0,5sek)

5,0 second - average-rate=(0+0+0+0+0+0+2+2+2+2+2+2+1+1+1+1)/8=2000Kbps, average-rate > burst-threshold -> Burst not allowed -> Actual-rate=2Mbps (1Mb per 0,5sek)

5,5 second - average-rate=(0+0+0+0+0+2+2+2+2+2+2+1+1+1+1+1)/8=2125Kbps, average-rate > burst-threshold -> Burst not allowed -> Actual-rate=2Mbps (1Mb per 0,5sek)

6,0 second - average-rate=(0+0+0+0+2+2+2+2+2+2+1+1+1+1+1+1)/8=2250Kbps, average-rate > burst-threshold -> Burst not allowed -> Actual-rate=2Mbps (1Mb per 0,5sek)

6,5 second - average-rate=(0+0+0+2+2+2+2+2+2+1+1+1+1+1+1+1)/8=2375Kbps, average-rate > burst-threshold -> Burst not allowed -> Actual-rate=2Mbps (1Mb per 0,5sek)

7,0 second - average-rate=(0+0+2+2+2+2+2+2+1+1+1+1+1+1+1+1)/8=2500Kbps, average-rate > burst-threshold -> Burst not allowed -> Actual-rate=2Mbps (1Mb per 0,5sek)

7,5 second - average-rate=(0+2+2+2+2+2+2+1+1+1+1+1+1+1+1+1)/8=2625Kbps, average-rate > burst-threshold -> Burst not allowed -> Actual-rate=2Mbps (1Mb per 0,5sek)

8,0 second - average-rate=(2+2+2+2+2+2+1+1+1+1+1+1+1+1+1+1)/8=2750Kbps, average-rate > burst-threshold -> Burst not allowed -> Actual-rate=2Mbps (1Mb per 0,5sek)

8,5 second - average-rate=(2+2+2+2+2+1+1+1+1+1+1+1+1+1+1+1)/8=2625Kbps, average-rate > burst-threshold -> Burst not allowed -> Actual-rate=2Mbps (1Mb per 0,5sek)

9,0 second - average-rate=(2+2+2+2+1+1+1+1+1+1+1+1+1+1+1+1)/8=2500Kbps, average-rate > burst-threshold -> Burst not allowed -> Actual-rate=2Mbps (1Mb per 0,5sek)

9,5 second - average-rate=(2+2+2+1+1+1+1+1+1+1+1+1+1+1+1+1)/8=2375Kbps, average-rate > burst-threshold -> Burst not allowed -> Actual-rate=2Mbps (1Mb per 0,5sek)

10,0 second - average-rate=(2+2+1+1+1+1+1+1+1+1+1+1+1+1+1+1)/8=2250Kbps, average-rate > burst-threshold -> Burst not allowed -> Actual-rate=2Mbps (1Mb per 0,5sek)

10,5 second - average-rate=(2+1+1+1+1+1+1+1+1+1+1+1+1+1+1+1)/8=2125Kbps, average-rate > burst-threshold -> Burst not allowed -> Actual-rate=2Mbps (1Mb per 0,5sek)

11,0 second - average-rate=(1+1+1+1+1+1+1+1+1+1+1+1+1+1+1+1)/8=2000Kbps, average-rate > burst-threshold -> Burst not allowed -> Actual-rate=2Mbps (1Mb per 0,5sek)

11,5 second - average-rate=(1+1+1+1+1+1+1+1+1+1+1+1+1+1+1+1)/8=2000Kbps, average-rate > burst-threshold -> Burst not allowed -> Actual-rate=2Mbps (1Mb per 0,5sek)

12,0 second - average-rate=(1+1+1+1+1+1+1+1+1+1+1+1+1+1+1+1)/8=2000Kbps, average-rate > burst-threshold -> Burst not allowed -> Actual-rate=2Mbps (1Mb per 0,5sek)

12,5 second - average-rate=(1+1+1+1+1+1+1+1+1+1+1+1+1+1+1+1)/8=2000Kbps, average-rate > burst-threshold -> Burst not allowed -> Actual-rate=2Mbps (1Mb per 0,5sek)

13,0 second - average-rate=(1+1+1+1+1+1+1+1+1+1+1+1+1+1+1+1)/8=2000Kbps, average-rate > burst-threshold -> Burst not allowed -> Actual-rate=0Mbps (0Mb per 0,5sek)

13,5 second - average-rate=(1+1+1+1+1+1+1+1+1+1+1+1+1+1+1+0)/8=1875Kbps, average-rate > burst-threshold -> Burst not allowed -> Actual-rate=0Mbps (0Mb per 0,5sek)

14,0 second - average-rate=(1+1+1+1+1+1+1+1+1+1+1+1+1+1+0+0)/8=1750Kbps, average-rate > burst-threshold -> Burst not allowed -> Actual-rate=0Mbps (0Mb per 0,5sek)

14,5 second - average-rate=(1+1+1+1+1+1+1+1+1+1+1+1+1+0+0+0)/8=1625Kbps, average-rate > burst-threshold -> Burst not allowed -> Actual-rate=0Mbps (0Mb per 0,5sek)

15,0 second - average-rate=(1+1+1+1+1+1+1+1+1+1+1+1+0+0+0+0)/8=1500Kbps, average-rate > burst-threshold -> Burst not allowed -> Actual-rate=0Mbps (0Mb per 0,5sek)

15,5 second - average-rate=(1+1+1+1+1+1+1+1+1+1+1+0+0+0+0+0)/8=1375Kbps, average-rate < burst-threshold -> Burst is allowed -> Actual-rate=0Mbps (0Mb per 0,5sek)

16,0 second - average-rate=(1+1+1+1+1+1+1+1+1+1+0+0+0+0+0+0)/8=1250Kbps, average-rate < burst-threshold -> Burst is allowed -> Actual-rate=0Mbps (0Mb per 0,5sek)

16,5 second - average-rate=(1+1+1+1+1+1+1+1+1+0+0+0+0+0+0+0)/8=1125Kbps, average-rate < burst-threshold -> Burst is allowed -> Actual-rate=0Mbps (0Mb per 0,5sek)

17,0 second - average-rate=(1+1+1+1+1+1+1+1+0+0+0+0+0+0+0+0)/8=1000Kbps, average-rate < burst-threshold -> Burst is allowed -> Actual-rate=2Mbps (1Mb per 0,5sek)

17,5 second - average-rate=(1+1+1+1+1+1+1+0+0+0+0+0+0+0+0+1)/8=1000Kbps, average-rate < burst-threshold -> Burst is allowed -> Actual-rate=4Mbps (2Mb per 0,5sek)

18,0 second - average-rate=(1+1+1+1+1+1+0+0+0+0+0+0+0+0+1+2)/8=1125Kbps, average-rate < burst-threshold -> Burst is allowed -> Actual-rate=4Mbps (2Mb per 0,5sek)

18,5 second - average-rate=(1+1+1+1+1+0+0+0+0+0+0+0+0+1+2+2)/8=1250Kbps, average-rate < burst-threshold -> Burst is allowed -> Actual-rate=4Mbps (2Mb per 0,5sek)

19,0 second - average-rate=(1+1+1+1+0+0+0+0+0+0+0+0+1+2+2+2)/8=1375Kbps, average-rate < burst-threshold -> Burst is allowed -> Actual-rate=4Mbps (2Mb per 0,5sek)

19,5 second - average-rate=(1+1+1+0+0+0+0+0+0+0+0+1+2+2+2+2)/8=1500Kbps, average-rate = burst-threshold -> Burst not allowed -> Actual-rate=2Mbps (1Mb per 0,5sek)

20,0 second - average-rate=(1+1+0+0+0+0+0+0+0+0+1+2+2+2+2+1)/8=1500Kbps, average-rate = burst-threshold -> Burst not allowed -> Actual-rate=2Mbps (1Mb per 0,5sek)

20,5 second - average-rate=(1+0+0+0+0+0+0+0+0+1+2+2+2+2+1+1)/8=1500Kbps, average-rate = burst-threshold -> Burst not allowed -> Actual-rate=2Mbps (1Mb per 0,5sek)

21,0 second - average-rate=(0+0+0+0+0+0+0+0+1+2+2+2+2+1+1+1)/8=1500Kbps, average-rate = burst-threshold -> Burst not allowed -> Actual-rate=2Mbps (1Mb per 0,5sek)

21,5 second - average-rate=(0+0+0+0+0+0+0+1+2+2+2+2+1+1+1+1)/8=1625Kbps, average-rate > burst-threshold -> Burst not allowed -> Actual-rate=2Mbps (1Mb per 0,5sek)

22,0 second - average-rate=(0+0+0+0+0+0+1+2+2+2+2+1+1+1+1+1)/8=1750Kbps, average-rate > burst-threshold -> Burst not allowed -> Actual-rate=2Mbps (1Mb per 0,5sek)

22,5 second - average-rate=(0+0+0+0+0+1+2+2+2+2+1+1+1+1+1+1)/8=1875Kbps, average-rate > burst-threshold -> Burst not allowed -> Actual-rate=2Mbps (1Mb per 0,5sek)

23,0 second - average-rate=(0+0+0+0+1+2+2+2+2+1+1+1+1+1+1+1)/8=2000Kbps, average-rate > burst-threshold -> Burst not allowed -> Actual-rate=2Mbps (1Mb per 0,5sek)

23,5 second - average-rate=(0+0+0+1+2+2+2+2+1+1+1+1+1+1+1+1)/8=2125Kbps, average-rate > burst-threshold -> Burst not allowed -> Actual-rate=2Mbps (1Mb per 0,5sek)

24,0 second - average-rate=(0+0+1+2+2+2+2+1+1+1+1+1+1+1+1+1)/8=2250Kbps, average-rate > burst-threshold -> Burst not allowed -> Actual-rate=2Mbps (1Mb per 0,5sek)

24,5 second - average-rate=(0+1+2+2+2+2+1+1+1+1+1+1+1+1+1+1)/8=2375Kbps, average-rate > burst-threshold -> Burst not allowed -> Actual-rate=2Mbps (1Mb per 0,5sek)

25,0 second - average-rate=(1+2+2+2+2+1+1+1+1+1+1+1+1+1+1+1)/8=2500Kbps, average-rate > burst-threshold -> Burst not allowed -> Actual-rate=2Mbps (1Mb per 0,5sek)

25,5 second - average-rate=(2+2+2+2+1+1+1+1+1+1+1+1+1+1+1+1)/8=2500Kbps, average-rate > burst-threshold -> Burst not allowed -> Actual-rate=2Mbps (1Mb per 0,5sek)

26,0 second - average-rate=(2+2+2+1+1+1+1+1+1+1+1+1+1+1+1+1)/8=2375Kbps, average-rate > burst-threshold -> Burst not allowed -> Actual-rate=2Mbps (1Mb per 0,5sek)

26,5 second - average-rate=(2+2+1+1+1+1+1+1+1+1+1+1+1+1+1+1)/8=2250Kbps, average-rate > burst-threshold -> Burst not allowed -> Actual-rate=2Mbps (1Mb per 0,5sek)

27,0 second - average-rate=(2+1+1+1+1+1+1+1+1+1+1+1+1+1+1+1)/8=2125Kbps, average-rate > burst-threshold -> Burst not allowed -> Actual-rate=2Mbps (1Mb per 0,5sek)

27,5 second - average-rate=(1+1+1+1+1+1+1+1+1+1+1+1+1+1+1+1)/8=2000Kbps, average-rate > burst-threshold -> Burst not allowed -> Actual-rate=2Mbps (1Mb per 0,5sek)

28,0 second - average-rate=(1+1+1+1+1+1+1+1+1+1+1+1+1+1+1+1)/8=2000Kbps, average-rate > burst-threshold -> Burst not allowed -> Actual-rate=2Mbps (1Mb per 0,5sek)

28,5 second - average-rate=(1+1+1+1+1+1+1+1+1+1+1+1+1+1+1+1)/8=2000Kbps, average-rate > burst-threshold -> Burst not allowed -> Actual-rate=2Mbps (1Mb per 0,5sek)

29,0 second - average-rate=(1+1+1+1+1+1+1+1+1+1+1+1+1+1+1+1)/8=2000Kbps, average-rate > burst-threshold -> Burst not allowed -> Actual-rate=2Mbps (1Mb per 0,5sek)

29,5 second - average-rate=(1+1+1+1+1+1+1+1+1+1+1+1+1+1+1+1)/8=2000Kbps, average-rate > burst-threshold -> Burst not allowed -> Actual-rate=2Mbps (1Mb per 0,5sek)

30,0 second - average-rate=(1+1+1+1+1+1+1+1+1+1+1+1+1+1+1+1)/8=2000Kbps, average-rate > burst-threshold -> Burst not allowed -> Actual-rate=2Mbps (1Mb per 0,5sek)

30,5 second - average-rate=(1+1+1+1+1+1+1+1+1+1+1+1+1+1+1+1)/8=2000Kbps, average-rate > burst-threshold -> Burst not allowed -> Actual-rate=0Mbps (0Mb per 0,5sek)

31,0 second - average-rate=(1+1+1+1+1+1+1+1+1+1+1+1+1+1+1+0)/8=1875Kbps, average-rate > burst-threshold -> Burst not allowed -> Actual-rate=0Mbps (0Mb per 0,5sek)