How long does it take to upload a 11 meg tiff file to a server in Germany, via scp on a 56 k modem?
Answer in extended entry.
I’m still waiting for it to finish. That’s your answer.
How long does it take to upload a 11 meg tiff file to a server in Germany, via scp on a 56 k modem?
Answer in extended entry.
I’m still waiting for it to finish. That’s your answer.
Maybe you should move to Florida now, so you won;t have to be kept on life support while you’re waiting.
But why a tiff file? Wouldn;t something compressed, like jpeg have been better?
Off the top of my head, a 1 MB file should take about 4 minutes via a 56K modem under normal conditions. So 11 megs should take about 44 minutes, unless there are router slowdowns or network congestion between here and there. Often the congestion between here and Europe originates in Canada for some strange reason.
Hello.
According to my calculations an 11,000,000 byte file takes about 250 seconds (4 minutes) to up/download at the best possible speed a 56K phone modem can generally produce (ie. 44,000 bytes/second).
This isn’t too bad a file in size to send overseas. However,iIt’s a good idea Kate to ask the receiving party in Germany that you will send them a file (with its size noted) first in a seperate email, then when they approve, send it as an attachment in the next email.
Deutsche Telekom had ridiculously high phone rates for many years in Germany. If I am not mistaken they were billing by the minute, even second. If you didn’t have ADSL, internet surfing was prohibitively expensive. It’s been about 18 months since I have been there last, so I am not sure if there has been an improvement in the regular phone rates in the mean time. Nonetheless, my friends and family overseas have long let me know that email attachments should be kept small in size.
Cheers
Not going by email – I’m using a secure file transfer protocol directly into the server. The jpg version is already up.
And it’s still uploading. A lot of the problem is lag, the rest is that the 56K speed is a gross exaggeration.
Stop being so cheap and get a satellite dish already! I’ve already got mine on order for when I move out to the farm.
Er, several points:
1. 56K modems transmit (optimally) at 56 kilobits per second, not 56 kilobytes per second. Assuming that you’re getting 100% throughput, an 11 Meg file should take about 1,609 seconds to transmit, or approximately 27 minutes.
2. Network congestion and Tx/Rx negotiations (including exchange of checksums etc.) reduce transmission speed to around 60 to 70% of the optimal capacity, so you’re looking at around 41 minutes for this file.
3. The above assumes error-free transmission. If there are errors, blocks of data will get re-transmitted, increasing the time still further. If the connection between Canada and Germany is noisy, you could easily be looking at a 50% re-transmission rate, so up your time from 41 minutes to around an hour or so.
4. Items 2 and 3 above are necessarily guesstimates. 😉
Sean, keep in mind that satellite dishes are great for downloads, but that’s all. You can’t broadcast (upload)from your dish to the satellite. Unless something has changed since I last read about this… (then I would of course retract this blurb)
🙂
Hopefully, the transmission will have finished by _now_; however, just to clarify a few things:
1) I’m not sure exactly what the protocol stack is at the server; let’s assume it’s FTP/TCP/IP (i.e. that the security doesn’t become part of the stack per se). This stack adds a significant overhead to the overall transmission, although one can’t calculate the exact overhead without knowing what options may be in use, or the packet size.
2) A dialup connection will (typically) use the Point-to-Point Protocol (PPP; RFC1661) over the dialup link. This adds a PPP header to the packet (although if IP header compression is used, the transmitted packet can be reduced in size).
3) The “56K” is a theoretically optimal download speed. Upload is more likely to be about 33Kbps.
http://www.56k.com/cons/downonly.shtml
4) The TCP protocol puts a limited number of “packets in flight” simultaneously, so the data transfer rate is a function of the “round trip time” (RTT) for the connection. In a dialup connection, though, the RTT is usually dominated by the slow link so we can usually assume the link will be fully utilized without much error in our answer.
5) As previously noted, any packet errors or loss will result in retransmissions – and depending on the nature of the error, can insert significant gaps in the “packet train”, increasing the overall transmission time.
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Satellites are two-way nowadays, have been for a while. Their big problem (aside from weather) is latency.
I remember when I was on dialup here in the province. 56K was something we never even saw realistically because of the noise of the rural lines. I don’t remember how fast it ever got, but I do remember it would transfer about 4 megs an hour.
Dialup was so absolutely painful, and at the time satellite was not even a remote option.