[c-nsp] Conditional advertise-map

[Gert Doering]

Hi,

On Wed, Sep 15, 2010 at 06:38:26PM +0100, Heath Jones wrote:
> I thought you'd say that...
> 
> There is absolutely *NO* reason why an additional entry needs to occupy
> space in TCAM in this case.
> If you have 2 contiguous prefixes that can be directly aggregated to a
> single prefix on the next subnet boundary, and that share the same
> next-stage-treatment (egress, queueing etc), they can take up only 1 spot.
> If a router isn't preprocessing routing information before it goes to the
> forwarding plane, then its not efficiently using the expensive resources..

Well, the theory agrees with you.  Unfortunately, routers out there in
the market (and remember, this is *cisco*-nsp) don't do this.

I have asked for it for a number of times, but it's a tricky problem
(like: you have a /16 that encompasses 256 /24, the RIB barely fits
into the FIB space, and then the /16 goes away -> 253 extra FIB entries
needed -> non-deterministic boom) *and* Cisco has no commercial interest
in spending lots of engineering effort to the goal of selling *less* 
expensive hardware...

gert

-- 
USENET is *not* the non-clickable part of WWW!
                                                           //www.muc.de/~gert/
Gert Doering - Munich, Germany                             gert at greenie.muc.de
fax: +49-89-35655025                        gert at net.informatik.tu-muenchen.de
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