From owner-freebsd-hackers  Fri Dec  7  9: 7:59 2001
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Date: Fri, 7 Dec 2001 12:07:42 -0500
From: Steve Ames <steve@virtual-voodoo.com>
To: Lars Eggert <larse@ISI.EDU>
Cc: Anders Hagman <anders.hagman@netplex.se>,
	freebsd-hackers@FreeBSD.ORG
Subject: Re: Nat through two DSL
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References: <5.0.2.1.0.20011207131945.009fe1d0@mail.training.telia.se> <3C10F658.6070001@isi.edu>
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On Fri, Dec 07, 2001 at 09:03:20AM -0800, Lars Eggert wrote:
> Anders Hagman wrote:
> 
> >I want to load share between two ADSL modems using a NAT/Firewall.
> >
> >Computer 1 \
> >            \                                     /-- ADSL 1
> >             \                                   /
> >Computer 2 ------ Wireless LAN --- Firewall/NAT -
> >    .        /                                   \
> >    .       /                                     \-- ADSL 2
> >Computer 10/
> >
> >The ADSL are 500k links and I want to load share on session by session.
> >Can I do NAT between an inside interface and two outside interfaces 
> >acting in a round robin fashion?
> 
> This may not be the good idea you'd think on first glance. If one of the 
> paths has a slightly different RTT (and they're pretty much guaranteed 
> to), you'll see out-of-order delivery at the receiver. I remember seeing 
> some study that showed that TCP doesn't react too nicely under such 
> conditions (it works, but not at peak performance).

Is it even possible to do use two upstream paths for redundancy? I tried
(very briefly while I had two broadband connections while switching from
one to the other) to get that to work and wasn't very successful.

-Steve

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