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Date:      27 Apr 2002 16:30:53 -0500
From:      Adam Wood <woodfucius@attbi.com>
To:        "J.M. Warenda" <warendaj@comcast.net>
Cc:        freebsd-questions@FreeBSD.ORG
Subject:   Re: regarding natd and FreeBSD
Message-ID:  <1019943053.2427.16.camel@wood.woodfucius.com>
In-Reply-To: <003601c1ee2a$cfc4c1a0$4500a8c0@benslm01.pa.comcast.net>
References:  <003601c1ee2a$cfc4c1a0$4500a8c0@benslm01.pa.comcast.net>

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On Sat, 2002-04-27 at 15:33, J.M. Warenda wrote:
>     Is anyone out there using a FreeBSD machine with natd on a cable modem
> to hook their LAN up to the net?  I've been doing this for a while now with
> FreeBSD 4.4-RELEASE on my spare Pentium 166 with 64 megs of ram and two
> Netgear FA311 ethernet cards.  I originally followed the documentation on
> natd to set it up and I've had essentially no problems with this setup, it's
> been smooth as silk, with one exception.
> 
>     If I send files or other data upstream *through* the natd system (i.e.
> from a machine on the LAN to a machine elsewhere on the net) I have no
> problems what so ever ... but if data is sent from the FreeBSD system
> *itself* ... for instance someone remotely logging into my private FTP and
> transfering data ... the connection gets totally killed.  Latency across the
> natd router goes through the roof.  At first I thought I must be hitting
> some kind of upstream cap, but I get much better xfer rates and no crippling
> latency if I send from a machine on the LAN.
> 
>     If this is terribly obscure I appologize, but I've had this problem for
> a while now and I can't quite wrap my brain around this one ... ftpd on the
> natd machine sending a file to a remote client on the net cripples the
> connection with latency, but sending data (for instance with an ICQ file
> transfer from a windows machine on the LAN) *through* the natd router
> doesn't have the same effect.  Has anyone encountered this?  Any ideas on
> what might cause it and how to address it?
> 
> -John

I have pretty much the exact same setup as you - cable modem into a
FreeBSD gateway with two nics doing NAT for 2 linux/windows dual boot
machines on an internal LAN.  I also run an ftp server for friends,
family, etc.

What kind of transfer rates are you getting when someone sends a file
from one of your LAN machines versus when the FreeBSD machine sends a
file through ftpd?  Are you running any kind of a firewall on the
FreeBSD machine that may be interfering with ftp transfers from the
outside internet?

Keep in mind that since most broadband providers cap the upstream at 128
kilobits per second (16 kilobytes per second), that is the fastest that
you are going to be able to send anything regardless of which machine
sends it.  I had a friend complain about slow ftp transfers of 10
kilobytes per second, and I explained to him that he was getting 63% of
my maximum available upstream bandwidth, which I didn't think was too
bad.

Also, since cable modem networks are shared not switched, your upstream
can slow down during heavy usage times (early evening when kids are home
from school, parents are home from work, etc.) and may not reach the 128
kbps/16kBps maximum.

-Adam



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