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