FTP transfer of 337MB file on 6M pipe should take how long

Posted on 2014-08-29
Last Modified: 2014-09-02
Hello EE,

I have a FTP server that a user is sending 337 MB through on a 6MB T1.  I am wondering what the calculation would be for how long this upload may take.
Question by:operationsIT
    LVL 22

    Expert Comment

    There are many considerations that would go into answering this.

    There are a few questions as well. T1 lines transfer at 1.544 megabits per second. This translates to 0.193 megabytes per second.

    So, if there are no other considerations, (dropped packets, other traffic on the lines etc.) then the math is:
    337 / 0.193 = 1,747 (rounded up)
    to get minutes, you would divide by 60
    1747 /60 = 29.1 minutes.

    So, under ideal conditions, it should take approximately half an hour to transfer a 337MB file over a T1 line.

    If you're connection is 6 megabytes per second, then under ideal conditions it would be
    337 / 6 = 56.1 seconds.

    Hope this helps!


    LVL 57

    Accepted Solution

    Bartender_1's calculations are "technically" correct.  A T1 at 1.544 Mbits per second is 0.193 Mbytes per second (1.544/8).

    However that does not take into account any overhead.  Typically you 337want to divide bits per second by 10 to get closer to what real world though-put is.

    So a T1 really gets about 0.154 Mbytes so it would take about 37 minutes or so.

    Now if you have a 6Mbit connection that is made up of T1's (4 T1's) you may or may not get 6Mbits per second.  Typically connections made up of multiple links a single TCP connection only goes over 1 of the links.  So you may only get 0.154 Mbytes per second.  If the connection is setup to send traffic from a single TCP connection over all 4 links, then you could get up to 6 Mbits/second, which is about 0.6 MBytes/second.  That would be about 10 minutes.

    So either about 40 minutes or 10 minutes.  Both of these also assume that nothing else is using the connection at the same time and that the other side also has the same or faster network connection.

    If there is other traffic it will take longer.  If the other side has a slower link, it will take longer.

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