The size of the global routing table is a rapidly growing problem.
Several solutions have been proposed. These solutions commonly divide
the Internet into two parts, one for customers and one for providers,
where only provider addresses are globally routable. Packets destined
for customer addresses are tunneled through provider space. For this
process to work, there must be a mapping service that can supply an
appropriate provider-edge address for any given customer address. We
present a design for such a mapping service. We adhere to a "do no
harm" design philosophy: maintain all desirable features of the
current architecture without negatively affecting its security or
reliability. Our design aims to minimize delay and prevent loss in
packet encapsulation, minimize the number of new or modified devices,
and keep the level of control traffic manageable.