is transmission time real?

[Guest]

Hi everyone
I'd love to know if the transmission time displayed in a transfer window is
the real one, or how does the operating system calculate the time left for an
operation to finish? (operation: copying a file through a network)
thanks

 

[Guest]

Umm. I will assume that you mean, When the window comes up to copy it says
time remaining. That is just an estimate. The estimate is based on, if
nothing changes (such as bitrate over a connection) if it says 2 mins @ 2KBPS
then it will take approx. 2 minutes to complete, if it stays at 2KBPS. I hope
this is what you meant?

 

[Shenan Stanley]

I'd love to know if the transmission time displayed in a transfer
window is the real one, or how does the operating system calculate
the time left for an operation to finish? (operation: copying a file
through a network)

It's fairly inaccurate in most cases. It simply gets the total size of the
remote file by a simple function call, then it starts keeping time of how
long it takes to transfer.. So if it takes 60 seconds to transfer 1MB of
data and you are grabbing a 60MB file, then it's easy mathematically to
conclude it will take 60 minutes to get that file. That is essentially what
the status of file transfers is doing, but because a network is not
consistent like that, you may get a time, then speed up/slow down and your
time changes.. and this rinses and repeats several times in a given
transfer.

 

[V Green]

There are so many things that can interrupt
a network transfer that it can only be a guess
based on the last few seconds of transmission.

It'll be nearly correct IF that rate continues uninterrupted,
but there's a good chance collisions on the network will
occur, and it'll need to recalculate all over again.

Occasionally, the algorithm responsible for calculating
the time REALLY misfires, and tells me I've got
"23988719495867 minutes remaining, or some
such nonsense...

 

[Alex Nichol]

I'd love to know if the transmission time displayed in a transfer window is
the real one, or how does the operating system calculate the time left for an
operation to finish?

It appears to be obtained by dividing the amount of data left by a
measurement of the rate it is currently displaying for an IE download;
that appears to be taken from the moment you OKed where to save, so is
initially much too high, as there will be quite a bit retrieved by that
time while waiting for your OK. Other software may use an almost
instantaneous rate; so giving wild fluctuation