Policy Statement on Address Space Allocations

    Date:        Thu, 25 Jan 96 14:46:29 PST
    From:        Yakov Rekhter <yakov at cisco.com>
    Message-ID:  <199601252246.OAA23511 at hubbub.cisco.com>

I have deleted almost everyone form the cc list (as have others)
except I went further and deleted the IAB, IANA, etc as well...

    Would you assume that anyone whose address allocation follow
    "the current address allocation policy of the
    IANA/InterNIC/RIPE NCC/AP-NIC"
    is guaranteed 100% global Internet connectivity ?

Yakov, this is a patently silly question, as the answer is
either obviously yes by definition, or obviously no by
demonstration.

That is, one can define "the Internet" as being that set of
IP reachable nodes which has connectivity to all of the other
nodes in the set (and probably includes one specific node,
say a.root-servers.net, just to distinguish this one particular
set from other similar ones).

In that case, by definition, if you are part of the Internet
you are guaranteed 100% Internet connectivity - anyone you
can't reach isn't part of the Internet.

On the other hand, if we avoid precise definitions of what is
the Internet exactly, then I can clearly show you nodes that
generally consider themselves to be part of the Internet,
which no-one (but a very limited number of nodes) can reach,
and I expect many others can too, which easily shows that
no-one, anywhere, gets 100% Internet connecivity.

And I think you can see that address allocation policies
actually have nothing whatever to do with this.


However, Miguel does have a point, if Sprint choose to filter
routes so that an advertismennt of mine is not visible to
Sprint customers, then it is Sprint customers who are missing
connectivity to me.   I would only care on the assumption that
I really wanted to communicate with someone silly enough to
connect to a provider who would deliberately reduce their
connectivity.

We should also note however that filtering at /18 does not
necessarily need to reduce connectivity, Sean has said he
has that filter often enough, but he hasn't said that he
doesn't also have a few other (perhaps static) routes
of the form (say) 203.0/14 aimed at (say) MCI, so that
while MCI (for example) may want to be sending 203.0.x/24
routes towards Sprint, Sprint can ignore them, and still
retain connectivity to everyone.

Connectivity remains that way, with some planning, though
routing optimailty perhaps suffers, if MCI then had to hand
off packets for some 203.0.z to some other provider that Sprint
would (with full routing) have been able to reach directly.

With a little application, the large ISPs could actually
agree amongst themselves to divide up the routing table space
this way - each agreeing to accept routes of "longer than
optimal" prefix lengths for some subset of the entire table
space, accept routes from all the others for lengthy prefixes
and advertise only a short prefix route to all of them.

While not a long term solution to anything, this would allow
the current routing tables to to significantly reduced in all
of the default free routers, which would also reduce
the need to install draconian route filters throughout the net.

Some routes would be longer, however it seems (to me at least,
and certainly from imperfect knowledge) that this could
largely be restricted to an extra high speed hop at (or near)
the NAPs or other exchange points.   That is, if implemented
rationally this wouldn't require the providers maintaining
longer prefix routes that are otherwise filtered in other
providers to actually provide any long haul transit, just
in and out of a single router.

And last, as long as the routing  tables continue to fit,
anyone who wanted could continue accepting all the routes
from everyone - the effect would be that when a provider
was forced to filter to keep the routing system running that
connectivity need not be sacrificed.

kre