Shane Ronan wrote:
But in fact with local number portability, you cannot rely on the county code to tell you where to route a telephone call anymore.
Not. With geographical aggregation, you may route a call *anywhere* in the destination country. Geographical aggregation means carriers in a country is required to have rich and robust connectivity between them within the country as if the country is served by a single carrier, which actually was the case with ATT/PTT/NTT monopoly. Then, whichever international carrier is chosen by the caller, the international carrier looks up country-wise routing table to reach the country. When the call reaches some point in the destination country, the callee can be reached relying on rich connectivity in the country. Number portability database is looked up after the call reaches the destination country, which will be used for further intra-national routing, which do not affect country-wise aggregation of international routing table. But, as ISPs do not want to be regulated to have such rich intra-national connectivity in all the countries, geographically aggregated addressing is considered not acceptable by operator community of the Internet. Masataka Ohta