On Thu, Mar 15, 2001 at 09:59:53AM -0500, Kavi, Prabhu wrote:
Look at how local number portability (LNP) works. Before the phone call is connected, a translation is made between the logical number and the actual number. The actual number is based upon geography, and consists of country-code, area-code, local exchange, and then physical port number. As a result, the routing tables in telephone networks are small. For example, if you are in the US and need to call the UK, the network only needs one entry for all telephone networks in the UK (plus a few more for redundancy).
This translation/lookup function is only necessary once per call in a circuit-switched network. In a packet-switched network, it's required once per packet. For this reason, number portability on the internet and in the PSTN are quite different problems. Joe