On Wednesday 10 November 2004 02:24, Eric Scott wrote: > Yo; does anybody know where I can download Mandrake 10.1 PPC via http > instead of FTP? On the FTP mirrors I'm getting an average of about 9KB/s. > That just won't do when download 2100MB of data. My satellite broadband > has roughly a 600k down/4k up connection... .Yes, I said four up, not > forty. I don't know if this would slow down an FTP connection, it doesn't > make sense to me, but the point is it's download really really slow. > Anyway, I'd like to try http or something instead of ftp, and helpers?
Your 4 kB uplink can very well be affecting your transfer rate, as can the quality of your satellite channel. The way that IP protocol works (http AND ftp) Is that the sending device will send out Frames of data. By default the frames are a maximum of 4096 bytes long. Each frame is numbered. Once a default of 8 frames has been sent (The Window), then transmission will stop until an acknowlegment is received that the first frame arrived OK, when the next frame is then sent. So transmission consists of frames coming down and acks going back in a 'sliding window'. In a medium with high propagation delay (Satellites have I think a 150ms delay), then a situation can occur where the time taken to receive the acks is higher than the time it takes to send 8 frames of data, and the sender has to wait for acks before it can send the next frame. Also if the bandwidth of the return channel is very low the time it takes to send the acks will make an impact. To improve transmision in this environment you can increase the number of bytes in a packet . The command 'ifconfig eth0 mtu 8196' will double the number of bits in flight before a response is expected, or increase the size of the Window (sorry I do not know the command for that) But then you can run into another problem. If your medium has a high error rate then the probability of a frame error goes up with frame size and throughput can go down dramatically. Since you are getting only 9kB I suspect this may be already happening to you. You may get better throughput if you **reduce** the mtu of your frames. Or, of course the problem may simply be the quality of the mirror source you are downloading from. HTH derek -- www.jennings.homelinux.net http://twiki.mdklinuxfaq.org
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