Very nice explanation. Thanks for that.

On 3/1/10, Mohammad AbuShady <[email protected]> wrote:
> I see, thanks a lot, and for your question about where the speed is being
> show, it's both in the download window (firefox download window) and also a
> network speed monitor over the whole system, of course they don't show the
> same numbers but they both show the small increase in the start, and I don't
> really know what 'granularity' means.
>
> ~Coalwater~
>
>
> On Mon, Mar 1, 2010 at 1:33 AM, KwikOne <[email protected]> wrote:
>
>> You did not indicate "where" your download speed is being shown/
>> calculated, nor the time
>> granularity used. Quite often the speed spike are not really spikes
>> (especially when first
>> starting the download) because of the way the download speed is being
>> calculated and
>> as time goes on the download speed stays constant, or it will drop off
>> then stay constant.
>> Think of it this way (note the figures are just approximates as
>> illustration only with rounding)...
>> 1) download requested from server
>> 2) first bit of data arrives; calculated speed is roughly amount of
>> data / 1 ms. (smallest granularity)
>>    = very high speed (1000 times amount of data)
>>    (example - first chunk is 1400 Byte, this would give approx
>> 1,400,000 Byte/sec rate)
>> 3) next bit of data arrives; calculated speed is roughly total amount
>> of data / (time from first bit
>>    to second bit) = lower speed (unless the server is close enough
>> that you have < 1ms time)
>>    (example - second chunk 1400 Byte arrives 100 ms later which would
>> give approx
>>     2800 Byte for 100 ms. = 28,000 Byte/sec).
>> 4) next bit of data arrives (example 1400 Byte 100 ms later which
>> calculates out to
>>    4200 Byte in 200 ms. = 21,000 Byte/sec).
>> and so on... get the picture (it all depends upon how the calculations
>> are done)?
>> Notice how the rate is dropping off when in actual fact in this
>> example it is actually 14,000 Byte/sec.
>>
>>
>> On Feb 22, 7:37 pm, Coalwater <[email protected]> wrote:
>> > Well i noticed that i when ever i start a download, the download speed
>> > starts with a very high speed spike in the beginning that could reach
>> > up to 3x of my bandwidth, and last for like 3 to 10 secs then starts
>> > to gradually drop till it reaches my usual expected download speed,
>> > this isn't really a problem but i would really like to understand it
>> > from the networks point of view, how does it get past the ISP limit
>> > even if for a very short period of time, because i might think of
>> > using it to my advantage somehow if i understand it, Hope some
>> > networks guy around here could explain to me :D
>> > oh and it doesn't depend on the connection type nor the operating
>> > system, i saw this happen on cable connection and mobile broadband,
>> > windows and ubuntu so it doesn't have any thing to do with those
>> > differences.. oh and it works also with both normal single connection
>> > download and download accelerators that use multipart downloading
>>
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-- 
Anvesh Saxena

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