Re: [LARTC] Load Balance and SNAT problem.

From: Grant Taylor <gtaylor@riverviewtech.net>
To: lartc@vger.kernel.org
Subject: Re: [LARTC] Load Balance and SNAT problem.
Date: Wed, 27 Jun 2007 01:24:37 +0000	[thread overview]
Message-ID: <4681BC55.1080301@riverviewtech.net> (raw)
In-Reply-To: <7e47206b0706242007q487365d3gb7c12658b9669edd@mail.gmail.com>

On 6/26/2007 12:44 PM, Peter Rabbitson wrote:
> Can you elaborate on this? My only issue with the kernel route 
> balancing is that route caching can not be disabled entirely, so 
> traffic to the same site will leave via the same channel, regardless 
> if the other channel is empty or not. I know that it is technically 
> possible (kernel option CONFIG_IP_ROUTE_MULTIPATH_RANDOM), but it 
> will work only for globally routable addresses, while breaking NAT 
> badly.

This is a very good point that was not made in the referenced message. 
I do not have any rebuttal to this point.  This is the type of point 
that I was hoping to see before but did not.

My response to this is that you have a good point, something that in my 
opinion should be addressed by the kernel at some point.

> The reason I made my bold, as you call it, statement, is because 90% 
> of the time when someone is doing NAT, it is for a tightly joined 
> group, with similar interests - hence a lot of traffic duplication. 
> For instance if every user listens to the same online radiostation - 
> how would you work around it?

I don't know if the 90% as you say is accurate or not.  However if you 
are even remotely in the ball park, you have a good point. I have been 
around environments with nearly 1000 computers with very little in 
similarity between all the people.  I think this is really based on 
where NAT is used and how it is used.  If you are talking of many to one 
NAT I would agree with you.  However if you are talking about many to 
many NAT, I'll disagree with you.

I think that the scenarios you are thinking of would be best described 
as a small office / home office (a.k.a. SOHO), which would definitely 
qualify with what you are saying.  However there are a LOT of uses of 
NAT outside of SOHOs.  Given the prevalence of SOHOs doing NAT, I am 
willing to bet that you are correct.  But, this is why there are 
different types of solutions to this problem for them.

> Let me know your thoughts

With regard to streaming radio, I personally believe that it should be 
multicast so that it can be streamed in one time and have multiple 
recipients hear it.  Or there should be some sort of proxy that will 
download it and pass it back to multiple clients.  Of course, this is 
beyond the scope of this discussion and would be used in larger 
environments out side of the SOHOs that I think you are referring to.

Grant. . . .
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