> Now I'm curious, because I can't work out what you're referring to! Just a guess as to what was intended. The fact that when layering a network over another network requiers an address binding mechanism. ARP was the first, followed by inverse, reverse etc ARP mechanisms. The layering approach, despite its initial lack of elegance as compared with "more complete" approaches (such as that of ATM that defines down to the wire), has become THE major principle of modern communications (see ITU G.805/G.809). Y(J)S _______________________________________________ Ietf@xxxxxxxx https://www1.ietf.org/mailman/listinfo/ietf