Provider Independent addressing usage

[Pekka Savola <pekkas@netcore.fi>]

Hi,

I just read the recent PI addressing usage I-D.

Based on the quotes at the end of the I-D, it would appear that at least
some of my concerns are shared by others, but nonetheless, let's hope this
brings up something new.

Problems with the PI approach:

 1) people don't seem to want too specific routes in the DFZ.  With
current policies, I'd estimate 100-200 routes is the maximum. (though the
technical constraints are a couple of orders of magnitude larger).
Specifying these with prefix length may give the wrong impression, as the
space would be rather densely populated (minus the oceans, sahara etc.)

 2) because of non-specific advertisements, operators would be forced to
carry a lot of traffic not their own, or throw it out.  Neither is
acceptable, economically or from user's point-of-view.

 3) the only ones that could really gain from advertisements are
regional/area/etc. IX's that have a very high level of regional ISP
penetration; e.g. if address belongs to the region, it'd be reachable
through the members of an IX with over 99.9% probability.

 4) ISP's operating at the IX would have to advertise, among themselves,
full /48 routes.  In some regions, where there are dozens of millions of
Internet users, this is probably not an acceptable solution either.  So
the problem goes back to 2), but in smaller scale where there are
often _no_ IX's to exchange the traffic.

==>

So, it's often the case, e.g. in Europe, that a country has about one IX.
The PI solution would work if the prefix(es) of the region belonging to
that country were advertised to by that IX, and _everyone's_ (in that
country) /48 PI prefix be advertised within that IX (whether it's directly
associated, or a smaller client ISP of the peering bigger ISP).

Additionally there would have to be some peering with neighbouring IX's,
so the locations near the borders of a country could be sent to the right
country.

If this was not done, some regional ISP's would have to capture and carry
some traffic they have no idea if they can deliver or dumped.  Or, the
traffic could be sent to some smaller-than-regional IX's which by
definition didn't exist.

Take the netcraft web server count by domain for example
[http://www.netcraft.com/Survey/Reports/0106/bydomain/]; I think it's fair
to assume that each /48 site would have at least one if not more web
servers.  United Kingdom appears to have about 2.8 million, so say 3
million /48's.  Even if there were 10 IX's in the UK (distributed nicely
by geographical areas, no less), this would still be a whole lot of
specific /48 routes between participating ISP's.

These appear to be rather unscalable restrictions.

==>

So some portions of this resemble the optimal 6to4 relay router finding
issue (using anycast, for example); only, this is a about 2^28 times
bigger problem....

-- 
Pekka Savola                 "Tell me of difficulties surmounted,
Netcore Oy                   not those you stumble over and fall"
Systems. Networks. Security.  -- Robert Jordan: A Crown of Swords