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Date:      Thu, 30 May 2002 17:21:17 +0200
From:      Andre Oppermann <oppermann@pipeline.ch>
To:        Richard A Steenbergen <ras@e-gerbil.net>
Cc:        "Louis A. Mamakos" <louie@TransSys.COM>, Attila Nagy <bra@fsn.hu>, Luigi Iannone <Luigi.Iannone@lip6.fr>, freebsd-net@FreeBSD.ORG
Subject:   Re: MPLS
Message-ID:  <3CF6436D.ADA51D7F@pipeline.ch>
References:  <Pine.LNX.4.44.0205291108080.7798-100000@scribble.fsn.hu> <3CF4A64A.EE220611@pipeline.ch> <200205291413.g4TEDLRG075458@whizzo.transsys.com> <3CF4E483.2510639@pipeline.ch> <200205291522.g4TFMdRG076033@whizzo.transsys.com> <3CF4FCFC.3D760508@pipeline.ch> <20020529180204.GK33611@overlord.e-gerbil.net> <3CF51E7C.E9A47960@pipeline.ch> <20020529233411.GO33611@overlord.e-gerbil.net> <3CF5F4ED.369BCE83@pipeline.ch> <20020530150612.GP33611@overlord.e-gerbil.net>

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Richard A Steenbergen wrote:
> On Thu, May 30, 2002 at 11:46:21AM +0200, Andre Oppermann wrote:
> > The theorie about the LC-Trie is that it'll fit into L2 cache for the
> > entire default-free forwarding table.
> 
> Versus the reality of doing bit operations instead of byte operations. In
> my tests, the mtrie was always faster, even on a celeron with a piddly L2
> cache.

We'll find out. We're designing a framework into which different kinds
of tables can be implemented. We can move on to profiling then.

> > This might work on a decicated router system. FreeBSD is being used
> > for servers as well.
> 
> Please explain how that would not work for servers?

It would work but not optimal because the packet flow is different for
locally terminated/generated packets.

> > Also to not to change the userland/kernel interface wrt routing we have
> > to keep all prefixes in the kernel RIB. This means we have to be able to
> > do longest prefix matching.
> 
> This is a non sequitur. All routes will be available through the kernel
> RIB, but for exact matches only. When is a longest prefix match needed
> there?

When the routing daemon instructs us to remove the prefix 10.0.0.0/8
when we also have 10.0.0.0/9 and 10.128.0.0/9.

> > Anyway, I'm confident we'll come up with something that is well
> > balanced and much faster and more memory conserving than what we
> > have today with the patricia trie. (A default-free kernel RIB consumes
> > approx. 30MB of kernel memory in 4-STABLE/5-CURRENT at the moment).
> 
> Not to mention the outrageous amounts of memory consumed by the caching
> mechanism.

Where? Do you mean rt_metrics?

> Oh, and it should be able to support multiple nexthops per prefix, and
> load balance across them. I think even Linux has this support now, and an
> actual FIB.

Yes, and policy routing...

-- 
Andre

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