Re: BGP prefix filter list

[i3D.net - Martijn Schmidt <martijnschmidt () i3d net>]

Brocade (now Extreme) does this on their SLX platform to market 1M FIB boxes as 1.3M FIB boxes after compression. We 
went with the Juniper MX platform instead, the relatively small FIB size on the SLX being one of the main sticking 
points for me personally. 

Nowadays there are also some SLX models with a larger FIB, which don't need compression algorithms to accommodate the 
routing table growth for a couple of years.

Best regards,
Martijn 

On 20 May 2019 23:05:45 BST, William Herrin <bill () herrin us> wrote:
> On Fri, May 17, 2019 at 9:06 AM Baldur Norddahl
> <baldur.norddahl () gmail com>
> wrote:
>
> > Think about this way to save at least half the size of the FIB with
> two
> > transit providers: Find out which provider has the most prefixes
> going
> > their way. Make a default to them and a route-map that drops every
> route.
> > For the other provider, keep only the routes where they have better
> > routing. This way you only use FIB space for the smaller provider.
> > Everything else goes by default through the larger provider.
>
> Hi Baldur,
>
> The technique you describe was one variant of FIB Compression. It got
> some
> attention around 8 years ago on the IRTF Routing Research Group and
> some
> more attention about 5 years ago when several researchers fleshed out
> the
> possible algorithms and projected gains. As I recall they found a 30%
> to
> 60% reduction in FIB use depending on which algorithm was chosen, how
> many
> peers you had, etc.
>
> As far as I know there are no production implementations. Likely the
> extra
> complexity needed to process RIB updates in to FIB updates outweighs
> the
> cost of simply adding more TCAM. Another down side is that you lose the
> implicit discard default route, which means that routing loops become
> possible.
>
> Regards,
> Bill Herrin