[X4U] Mac mini as an Internet Gateway.

[Stroller]

On Dec 14, 2005, at 4:21 pm, Craig A. Finseth wrote:
> ...   If you want to use the Mac Mini as a (NAT) router then it won't 
> work. I
>    looked into this fairly extensively - admittedly under Linux rather
>    than Mac OS X, but it shouldn't make any difference - trying to 
> route
>    through a single physical interface causes packet collisions and
>    slowdowns & all manner of Bad Things. It might work _extremely 
> slowly_
> 	...
>
> It really depends on the load and various network speeds involved.
>
> If you've got a DSL line that tops out at a megabit and the Mini is
> hooked up at 100 Mbps, I don't see a problem.
>
> It also depends on the application load.

I can't quote any figures on it, so it'd be great to hear from someone 
who can, but I don't think we're talking that order of magnitude.

If you route on a single interface then IMMEDIATELY a packet comes in, 
the router acknowledges it on one interface and forwards it to another 
computer on ... erm... another interface that happens to be aliased to 
the same phyiscal ethernet socket. Bonkl! Bonk! Packet clash! The 
TCP/IP stack retransmits each of the packets after a random interval, 
but by that time more packets have come in.

I wouldn't be surprised to hear that a 100Mbps connection was slowed to 
less than kilobits, (ie less than the speed of the DSL connection) or 
if it just caused hideous instability, or killer unreliability in 
anything trying to use the network interface. When I read about this 
(two or three years ago) my initial reaction was that I wanted to do it 
anyway, but the experts whose opinion I was reading (Linux kernel 
programmers) expressed in such strong terms what bad practice it is 
that I decided they probably knew what they were talking about. By all 
means try it - I'd really love to hear your feedback after testing - 
but I think it'd be best not used on a production system without 
further research.

Stroller.