The essence of the architecture of mobility is to allow the identity of the mobile device to remain constant while allowing the identity of the location of the device within the network to vary. The dynamic DNS approach attempts to bind the domain name as the device's persistent identity and allows the current IP address to equate to the device's current location. Obviously, as already pointed out, the restriction here is that the device cannot support persistent state across location changes, but worse, as far as I can tell, is that it is an approach that has poor scaling properties. In order to operate correctly in a timely fashion the relevant parts of the DNS now require very short TTLs. At that point many of the assumptions of the scaleability of the DNS tend to be called into question. Is the gain worth the potential scaling pain? If the issue here is one of circumventing some level of circuitous traffic paths, then it seems to me that there is really not much to gain - any cursory examination of Internet paths in terms of cable route miles reveals a healthy level of gratuitous overhead in any case - the so called direct paths you get from dynamic DNS updates as a solution to mobility may well be no better than the dog-leg route you were attempting to avoid.