Filtering prefixes longer than /24

[Dorian Kim]

On Tue, Jul 10, 2001 at 07:56:37AM +0900, itojun@iijlab.net wrote:
> >The scaling of IPv6 wrt. routing table size is IMO a big non-issue; a
> >remnant from the '95 when people started to get worried about the growth
> >of DFZ.
> >
> >Nowadays 100,000 routes is no big deal.  Any "core" router which should be
> >able to get full internet table can deal with this without problems.  You
> >shouldn't be participating with your old 4500 Cisco with 16 MB of memory.
> >Thus, I don't see what's the point of trying to minimize the size with all
> >costs.
> 
> 	two comments:
> 	- core routers need to carry both IPv4 full routing table and IPv6
> 	  full routing table, until we phase out IPv4.
> 	  (or you need to babysit separate routers, separate fibers...)
> 	- routing table in IPv6 will eat 4 times more memory than IPv4
> 	  if the # of entries is the same.
> 	so I believe it is not a "non-issue" (or it is safer to think that way).

All good and valid points. Furthermore, real concern regarding routing
table size now, as was in mid 90s isn't so much to do with handling the 
memory requirements related to prefix table, but rather scaling the 
computational power necessary to do path computation in an Internet whose 
path diverity is increasing rapidly along with prefix table size.

There are networks today that are seeing internal prefix table size in excess 
of 200,000 prefixes and millions of paths.

When things grow faster than Moore's law for long enough, you lose, and
we've jumped back on that trajectory after the temporary breaking affects
post-CIDR.

Of course, when people need a multi-million-dollar-liquid-cooled-faster-than-
Cray-SV2 for every default free router, perhaps economic barrier to entry
will solve this problems for us...

-dorian