I would like to know is it advisable and what is the duration to go through an ISDN connection of 128K for a 10M file transfer?
This connection is setup this way for to find the cheapest cost available for the WAN connection setup.
if you are not having any download time restrictions you can make use of the simple/cheap medium to do the file transfer.
But if you have some kinda scheduled transfers which needs to be triggered in a routine time interval then you need to make sure that your existing transfer is done.
It may roughly take 15 to 20 mins to complete the transfer in your scenario.
you can refer the below link to get some idea about the same.