Hi,
On Thu, Nov 22, 2001 at 01:46:35PM -0800, Michael K. Smith wrote:
> >> *>i24.154.32.0/24 213.239.22.241 200 0 8918 701 7046 ?
> >> *>i24.154.33.0/24 213.239.22.241 200 0 8918 701 7046 ?
> >> *>i24.154.34.0/24 213.239.22.241 200 0 8918 701 7046 ?
> >> *>i24.154.35.0/24 213.239.22.241 200 0 8918 701 7046 ?
[..]
> > Even if 7046 has multiple links to 701, it would be possible to send
> > out a /20 *and* all the /24s, and tag the /24s as "do not export
> > elsewhere".
>
> What if 7046 has a connection to 1239 as well?
They don't, at least not in any way that is visible on the looking glasses
or in our BGP table.
We're not talking "what-if's" here. We're talking "people are garbaging
the whole world" here.
> If 701 announces the /20 as
> such, while 1239 announces the /24, traffic is going to follow the longest
> path every time.
A clear case for "aggregation in 1239 as well".
> > this means: 73,000 prefixes are there that are more specific than what the
> > registries allocate, read: "that are likely to be aggregateable to a LOT
> > less".
>
> That's because lots of ISP's have multihomed customers using a
> sub-allocation of their address space.
You cut the interesting paragraph: I didn't say that it's possible to
remove all of those 73000 prefixes. I estimated about 30000, and this
leaves lots of room for "multihomed sub-allocations".
Currently there are about 10,000 AS numbers in use. Can you give me a good
reason why this means 105,000 prefixes? Those "multihomed customers"
usually have *one* address block, meaning *one* prefix per AS.
> I am not arguing that there are misconfigured routers out there where people
> couldn't figure out the "mask" statement, but there are also lots of small
> providers trying to provide quality of service to their small markets by
> having more than one upstream provider.
This is not a way to provide quality of service to anybody.
Announcing poorly aggregated bullshit is a good way of providing very bad
quality of service. People have enough of this and WILL start filtering.
We already DO filter "more specific than /24". Saves about 2000 prefixes.
gert
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Gert Doering - Munich, Germany gert@greenie.muc.de
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