🚀 go-pugleaf

In article <Don75y.5o5@assip.csasyd.oz>,
	davidf@syd.csa.com.au (Dave Fitch) writes:
>johns@rd.scitec.com.au (John Saunders) writes:
>>Dave Fitch <davidf@syd.csa.com.au> wrote:
>>> Last Wednesday evening (~6pm) I ftp'ed several files from ANU's
>>> sunsite mirror (as announced here a couple of days ago, thanks!).
>>> I was fairly consistently getting 3.2 Kbytes/sec as reported by
>>> ftp when it finished getting each file.  What sort of rates do
>>> other people get??
>>
>>That's about the best you will get with a 28.8K modem link. The theoretical
>>maximum is 28800/8 = 3600 = 3.5K but there is TCP/IP overhead in each packet
>>to the tune of 40 bytes. Also PPP adds a few bytes to the packet. You might
>>be able to squeeze a tad more speed by upping the mtu and mru (assuming it's
>>set less than 1500 at the moment) but don't expect miracles.
>
>Oh (thanks).
>The mtu is set to 296, I changed it from 1500 to see what'd happen
>after I read somewhere (in the dip manpage?) that a smaller value
>was often better.

The smaller size improves responsiveness when running a telnet session
while ftp'ing at the same time. However the larger size improves throughput,
but makes the telnet session a pain. However the "Type Of Service" packet
prioritising in newer kernels helps interactive responsiveness a lot, even
with the larger MTU & MRU sizes.

>What's mru??

Maximum receive unit. Like mtu but in the other direction. Specifying mru
causes the other end to set it's mtu to the value specified. Normally you
would set them the same, although they don't have to be. I can't think of
much benefits of specifying different sizes.

>Is it worth setting the port speed to 115200 (or something higher than
>38400)??  Does this actually have any affect??  (as it's an internal
>modem, so not using the serial port)

Good question. It depends if the internal modem actually uses a UART, or
simply simulates the UART interface. The higher port speed can allow
better throughput on uncompressed data. But forget any improvement when
ftp'ing .ZIP (etc) files, some older V42.bis compression implementations
actually went slower on compressed files! If your computer can handle 115200
without overruns, then use it. Also make sure that VJ compression is not
disabled, the default for PPP is to use it. That saves having to send all 40
TCP/IP header bytes in each packet.

One tip, don't bother with BSD compression because your modem can do a
better job of compression, and compressing something twice in a row doesn't
make it any smaller (can actually make it larger). Also I have been having
problems with a PPP link using 'bsdcomp' that stops talking after a few
hundred K being transferred. Use -bsdcomp in the options file.

Cheers.
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