Tom Garner wrote:
>
> Hi !
>
> I have now got my system sorted so that I can run my Redhat 5.2/2.0.36 box
> as a PPP dialin server. It's a single line system runnig a Hayes 33600.
> Works really well, and *very* reliably.
>
> However, if I am transferring files using FTP, I typically get a 2560 cps
> transfer rate on a 28800 connection, which obviously doesn't leave a lot of
> bandwith for anything else. Is there any way I can "balance" things up a
> bit ?
>
> I need to know as it's possible that I may have to set up a similar system
> which uses more than serial port at a time, and performance will be a big
> issue, especially if one line hogs the system to the detriment of the other.
>
> Anyone got any ideas ?
I am running three Linux dialin servers:
P60/16 megs ppp2.3.5 kernel 2.0.36 external USR V90
PII260/64 megs ppp2.3.5 kernel 2.1.131 internal V.Fast
486/33 8 megs ppp2.2.0 kernel 1.2.8 external V34 Supra 28.8k and V34
33.6k USR Sportster
and at home:
PII/233/64 megs ppp2.3.5 kernel 2.1.131 external V34 Supra 28.8k
upgraded to 33.3K
The PII box is by far the fastest and most reliable, some web pages come
through at 11K/sec (for the rpm2html page at rufus.w3.org) but regular
2.9K/s for rpm files. I believe that the reason for this is that both
ppp ends are using compress_deflate which significantly reduces the
serial traffic to the modem. I am also told that internal modems
generally use an on-board 1K buffer whereas the usual 16550A UART /
external modem is only using a 16 byte buffer.
I notice that when I connect to the PII box my SD modem light hardly
filckers during download, but with the other two boxes there is quite a
lot of SD activity. This looks like error resend packets to me.
OK in none of the machines is the cpu load measurable, but with only a
16 byte buffer and the DTE serial connection running at 115,200 baud the
cpu has to be *very* attentive to emptying that tiny 16 byte buffer. On
the internal, there is a extra bonus of a 1K buffer.
There is a fair amount of conjecture here, but I believe that this is
what is happening. I don't think windows can use the bsd_compress or
deflate capabilities, but they can always upgrade to Linux.
Peter
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