[ppml] geo addressing

[Tony Li]

> what relationship does the network topology of today have to the
> network topology of tomorrow, and why, and how do you know?


Not to take sides in this argument, but one thing that we can observe
is the *general* locality of topology.  For example, an end site is most
likely to use a service provider in its local region rather than buy a
transcontinental link for access.

Similarly, we can make the generalization that service providers in
a given area will, at some point in the volume curve, choose to
interconnect locally rather than back-haul significant traffic volumes
to a distant interconnect only to have it return.

The primary drivers here are the obvious ones: geographic barriers
to interconnection result in an economic disincentive to interconnect.
We see this in the pricing of submarine bandwidth relative to
terrestrial bandwidth.  Similarly, simple distance is a disincentive to
create long-haul interconnect outside of long-haul networks, resulting
in additional locality.

Thus, as an example, two ISPs that are connected currently in the SF
  bay area are likely to remain connected within the bay area as
long as it remains in their economic interests to do so.  Assuming that
both survive as commercial entities and traffic volumes justify the  
link,
there is little incentive for the ISPs to instead sever the link and
interconnect in Washington D.C. instead.

This locality of topology can be exploited by an appropriately
constructed routing architecture, but it requires a slightly different
approach than the geographical addressing architectures that have
been discussed in the literature so far.

Regards,
Tony