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List:       inet-access
Subject:    RE: traffic estimates...
From:       "Rodolfo J. Paiz \(E-mail\)" <rpaiz () gold ! guate ! net>
Date:       2000-11-27 5:27:54
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> The page can contain results from up to 20 queries with a
> maximum return for each query of 51k.

First: when dividing from KB to MB, you overshot by a factor of 1K. Thus
your expected traffic is 1,024 times greater... about 25GB per day, or an
expected 340Kbps of average bandwidth used.

Second: You *have* noticed that each page could then be up to 1MB in size,
right? This means that it would take about 5 minutes to download on a 56Kbps
modem and about 2 minutes (120 seconds!) even on 128Kbps ISDN. Even on a
full T-1, for that single user and if you have bandwidth to spare, it's
about 10 seconds...

That's a big page, sir... and you're getting 600,000 of those per day? I'd
check carefully what the average size of the *actual* pages served is. It
may be a lot less. Also, assume some sort of bell curve for traffic since it
will *not* be evenly distributed. For example...

Load    4 |             |||
        3 |          |||||||||
        2 |       |||||||||||||||
        1 |    |||||||||||||||||||||
          +-------------------------
     Hour   000000000011111111112222
            012345678901234567890123

Hours at load 0 = 3      Total Load  =  0
Hours at load 1 = 6      Total Load  =  6
Hours at load 2 = 6      Total Load  = 12
Hours at load 3 = 6      Total Load  = 18
Hours at load 4 = 3      Total Load  = 12
                ===                   ===
    Total Hours  24        Total Load  48

So, the 24 hours carry a total load of 48. Your total estimated traffic
(according to your numbers) is approximately 600GB/48 = 12.5GB per load
unit. At peak hours, you're handling 4 load units, thus you must be able to
handle up to 50GB per hour, not the 25GB you got.

End result: you need at least 768Kbps of real, all-the-time bandwidth to
serve this site. Since you always want to have some spare bandwidth (25%
margin minimum) I'd say you're looking at 1Mbps minimum contracted real
bandwidth.

Your estimates of the load curve will yield a more accurate picture, as will
your estimates of the average actual size of those pages.

--
Rodolfo J. Paiz
rpaiz@gold.guate.net <mailto:rpaiz@gold.guate.net>


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