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About LinkBacksHow long would it take to transfer a 170MB file over network at 54Mbps?
How long would it take to transfer a 170MB file over network at 54Mbps?
Far longer than you'd expect
I'd expect something in the order of 30 seconds?
no... more like 30 mins...
Originally Posted by Dareos
Thanks. Can I ask how you calculated that?
Just over 25 seconds... that's what it should take...
54Mb/s = 6.75MB/s
170/6.75=25.185
At least I think that's correct!!
Last edited by Allen; 31-01-2005 at 07:29 PM.
Well, you'll never see 100% utilization rates, plus you've got overheads for all the transmission protocols, packet headers, frames etc etc. Signal strength, noise etc will come into play too. I think suck it and see, but I'd be surprised if it was under five minutes.
Wireless is crap for sending large files across
Just tried it and it took 80 seconds. Admittedly thats on good link with the PCs involved being about 10 feet apart (vertically)
Thanks dude - that's really helpful!
Hence why I put the should in italics... obviously it'll never be as quick as it should be!
People often don't understand the term "bandwidth" and it creates common misconceptions and expectations.
Signalling rate is what the manufacturers of networking devices quote, the theoretical "if the world were perfect" rate at which raw data can be transferred.
Data throughput is the measured, actual speed of the transfer and is often between one quarter and one half of the signalling rate.
(People get confused and upset when their "gigabit" copper networks only perform at 280Mbps according to speed measuring tools.)
The "easy" sum has a few factors to take into account:
- Resource utilisation at either end; is the network in use, has the CPU a large overhead, etc.
- Signal strength and persistent connection; 100% signal strength is no good if it's "most of the time" but drops to 10% now and again
- Is 170MB 170,000,000 bytes, or 178,257,920 bytes?; files on disk are often reported in legacy base-2 megabyte format but "bandwidth" is thousands/millions of bits per second
- The application layer; what was used to copy the file, does it have its own integrity checking or bandwidth-throttling, etc.
Assuming 170MB = 178,257,920 bytes = 1,426,063,360 bits and estimate the data throughput at 1/3 of the signalling rate (18,000,000 bits/sec):
1,426,063,360 / 18,000,000 = 79.23 seconds
This is simplified quite a bit too, there are other factors to take into account, including environmental issues like interference.
There are 7 layers to the OSI network model and a file copy is using all of them, physical link layer through to application layer.
Of course, it's easy when you know the answer
1,426,063,360 / 80 = 17,825,792 bits/sec = 17.8Mbps
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TCP/IP only has 4 acctual layers though, OSI is only a model. (admitantly TCP/IP spans into all 7 OSI model layers as an overview)
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