OpenCyber AcademyLesson map
Lesson 16. Map, example, EX062.
flowchart TD
U["90 normal times and 3000 flood times, both sorted"] --> B["Bucket starts full"]
B --> R["Refill, then serve if a token remains"]
R --> L["Three printed settings"]
The third line is the first line that drops the normal client.
Logical drawing
limit=5/s burst=20 normal_served= 90/90 flood_served= 319/3000
limit=2/s burst=10 normal_served= 90/90 flood_served= 129/3000
limit=1/s burst= 5 normal_served= 62/90 flood_served= 64/3000
Learning outcomes
After this chapter, you should be able to:
- Read both 90/90 lines and the 62/90 line.
- Read the flood counts 319, 129 and 64.
- Treat the spaces in the third line as part of the format.
16.1 One generator, two sorted lists, three parameter pairs.
random.Random(4) draws 90 times from the uniform range [0, 60) and 3000 times from the same range. Each list is sorted, so the simulator sees increasing timestamps. The bucket starts full, with tokens = burst and last = 0. At each request it refills with min(burst, tokens + (t - last) * rate) and then serves the request if at least one token remains, decrementing by 1.
The pairs are (5, 20), (2, 10) and (1, 5). At 5 per second with burst 20, all 90 normal requests are served and 319 of 3000 flood requests are served. At 2 per second with burst 10, the normal client is still 90/90 and the flood falls to 129. The tight pair is the first to miss ordinary timestamps: 28 of the 90 go unserved, leaving 62, while flood survivors number 64. That pair is 1 per second with burst 5.
The format widths are part of the line. Burst uses width 2, so the third burst prints as a space and then 5. Normal uses width 3. Because the flood field reserves four columns, the two-digit value 64 is indented by two spaces. A transcription that closes those gaps has not copied the print.
Lesson table; scroll horizontally to read all columns →
| Setting | Normal | Flood |
|---|---|---|
| 5/s, burst 20 | 90/90 | 319/3000 |
| 2/s, burst 10 | 90/90 | 129/3000 |
| 1/s, burst 5 | 62/90 | 64/3000 |
16.2 Worked example
Lesson table; scroll horizontally to read all columns →
| Choice | What the print supports |
|---|---|
| Prefer 2/s burst 10 when the goal is to keep every normal request in this run | 90/90 remains, and the flood is 129 rather than 319 |
| Prefer 1/s because the flood is smallest | The normal client loses 28 of 90 requests |
| Invent a 3/s row | No such line was printed |
Synthetic case. The two clients are draws on a 60-second line. They are not Tallis staff.
Errors and limits
The smallest flood count is also the count that stops serving the ordinary series. Both columns decide the reading.
Apply
- EX062 — Three buckets. Which settings serve all 90 normal requests, what does the tight setting do, and which spaces belong in the third line?
Show marking criteria
Rubric: 3 = 90/90 then 90/90 then 62/90; floods 319, 129 and 64; the third line pads burst and the flood count;; 2 = the three pairs of counts;; 1 = one setting;; 0 = adds a row.