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# Calculating the peak source data rate

For an exam I am soon to sit there is a question I have no idea how to answer, it is in past papers but there is no explanation to work it out in our lecture slides. The question is:

A company requires high-quality video conferencing service. The holding times are between 1000 to 10000 seconds. The Burstiness is 3 and the average data rate is between 1.5 - 15 Mb/s. Calculate the peak source data rate.

I've looked around on the net for information relating to this but I can't find anything. Can anyone figure out the formula necessary for this question?

I would really appreciate it.

Thanks
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pbzzs
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1 Solution

Commented:
That is a very odd academic question. How can an "average" be a range like that?
Anyway, if you are looking for a "peak" data rate, then you need to look at the max so we can use the 15 Mb/s as the "average" in the peak case.

How are you defining "holding time"? 10000 seconds is close to 3 hours. You can't do anything in that time with video conferencing. Is that really supposed to microseconds or nanoseconds? Is it how long to buffer a packet before dropping it? Holding time shouldn't affect data rate from the source.

What are the units in "burstiness"? What does 3 burstiness mean?

The most simplistic definition would say that burstiness of 3 means it bursts up to 3 times the data rate, so the peak data rate would be 45 Mb/s, but that looks too easy?
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Author Commented:
Yes I completely agree with this being an odd question, that's why I posted it - our lecturer is terrible, this question has been in the exam the last 2 years however his lecture notes do not in any way explain how to work this out. The closest I have got is:

peak source data rate = burstiness x average data rate

We know that burtsiness is 3 but average data rate we have to calculate. Assignment says that it is between 1.5 - 15 Mb/s so I will obtain mean average:

1.5 + 15 = 16.5 / 2 = 8.25.

Which gives:

peak source data rate = 3 x 8.25 Mb/s = 24.75 Mb/s

But this completely ignores the holding time.
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Commented:
Holding time should not affect peak source rate. That data is just in there to trick you. For peak rate, you should use the worst case average of 15, so 45 would be the peak.

Now that you defined things a bit better, I am confident that 45 is the expected answer. It's the peak, so it means the max.
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