Why file transfer is taking longer time over network here?

First of all your calculation of time is wrong - in theory it should be 5 mins instead of 10. There is no buffer at Your ISP that would stop and cache the data before continuing to another network. Data transfer goes as fast as the slowest link in chain allows it - thus if both networks have 4 Mbps then the speed should be minimum of (4 Mbps, 4 Mbps) = 4 Mbps and thus 140 MB / 4 Mbps = 280 seconds.

This, however, doesn't apply to long distance transfers. Your ISP and the ISP of your client offer 4 Mbps speed, but only to their parent network. They generally can't guarantee you the same speed to another country or continent because they have no control over it.

These transfers depend on other factors like parent network load or bandwidth limit allowed to your ISP, etc. Many consumer-grade ISPs don't offer special plans specific for long distance transfers.

Marek Rost

Posted 2016-09-10T10:03:57.523

Reputation: 1 826

First of all your calculation of time is wrong - in theory it should be 5 mins instead of 10 its 10 mins because of 5 + 5. 5 mins from my computer to my ISP and 5 mins for client ISP to client computer. Hope you agree. – user3198603 – 2016-09-10T11:45:53.953

Regarding This, however, doesn't apply to long distance transfers. Your ISP and the ISP of your client offer 4 Mbps speed, but only to their parent network. Per mine understanding all ISP's are connected physically (thru internet exchange either fiber optics or some other medium), So what do you mean by parent network here ? – user3198603 – 2016-09-10T11:48:00.967

@user3198603 1. That would be true, if the file was first saved at your ISP and THEN traveled to the client's location - but you're transfering it directly. - Here is a paralel example: You want to transfer 14 m^3 of water. You feed the water into pipe with speed 4 liters per second and client extracts it at 4 liters per second - the pipe allows transfer speed 4 liters per second. You can't feed faster, because the pipe cannot inflate. The client can't remove water faster because the pipe would empty out. Thus it will take 14*1000/4 = about 4 hours. – Marek Rost – 2016-09-10T12:07:53.833

@user3198603 2. ISPs are generally connected to a country-wide network, which then connects to international network. At each connection point there are huge network switches and even those switches have limit to how much data they can transfer at once. It's not problem of transfer speed - light and electrons travel almost instantly, but there is a limit on how much data can you transfer at same time. Hope this explained it a bit. – Marek Rost – 2016-09-10T12:14:08.890

@Mark Rost Regarding parallel i was under impression when i say 4Mbps its speed b/w my moden and my ISP.. I mean with in 1 sec , 4Mbdata will be travelled to my ISP but cover further distance like to client ISP. It will take more time. What i get from answer distance is not a constraint here. With in 1 second , 4Mb data will be transferred across any distance . Right ? – user3198603 – 2016-09-10T12:21:19.737

For ISPs are generally connected to a country-wide network(CWN)... yes it clarified. But one point on this are ISP connected to CWN physical medium, similarly for CWN to IN? – user3198603 – 2016-09-10T12:24:31.630

@user3198603 exactly, to add another example: it's like highway where cars travel with nearly infinite speed - the problem is there is very limited number of paralel lanes. As for the network layout: Yes, but they can be connected on multiple places and some data transfer might be realized by satelites instead of cables. But same rules apply - speed is nearly infinite, but the demand for data transfer at same time is higher than technology allows through - that's why there are limits. – Marek Rost – 2016-09-10T12:32:37.557

Thanks Mark a lot . Can you reply mine last comment too i.e. are ISP connected to company wide network (CWN) physical medium, similarly for CWN to International network? – user3198603 – 2016-09-10T12:45:57.297

@user3198603 i'm not sure what you mean by similarly - the logic isn't really different - the device connecting networks together has a routing table, which tells it where to send data. If you compare it to home-grade router or switch, it will naturally be much more powerfull and the function might be split into several physical devices, so it can work faster. I don't really have futher knowledge about specific hardware used for transfer of such large quantities of data... – Marek Rost – 2016-09-10T13:31:03.637

Sorry if i confused you. Mine question is simply are ISP connected to company wide network (CWN) through physical medium like fibre optics ? – user3198603 – 2016-09-10T13:49:24.653

generally yes - but don't have to be. If ISP works in very remote location, they could have satellite uplink for example... – Marek Rost – 2016-09-10T14:07:10.143

Thanks What i get from this answer is here culprit can be parent network load like country wide network because of limit on switches . – user3198603 – 2016-09-10T14:12:07.627

yes - either physical limit of the devices or enforced by software - for example to make space for higher priority data transfer. I'd be guessing only. – Marek Rost – 2016-09-10T14:18:34.287

Why file transfer is taking longer time over network here?

Answers