I believe he understands just fine. However, his point (and I agree with him) is that if you are behind NAT, it isn't full end-to-end functionality, even if it does allow some degraded form of end-to-end connectivity with significant limitations which are not present in the absence of NAT.
"I can't use your address" is inherent in the network. "I can't use whatever port number I want on my side of the connection" is not. Owen On Feb 16, 2012, at 10:24 PM, Masataka Ohta wrote: > valdis.kletni...@vt.edu wrote: > >> No, you said specifcially that it can be restored by end system*S* >> plural. > > Yes, end to end connectivity is restored. > > However, that end to end connectivity is restored does not > mean your boxes can use 131.112.32.132 nor port 49734. > >> Yes, I can get one box listening. Now tell me how to get >> the second and third boxes listening on the same port. > > Perhaps, you misunderstand how end systems behind NAT > must interact with UPnP or something like that to be > able to restore the end to end connectivity. > > End systems behind UPnP boxes are allocated disjoint > sets of global port numbers, only among which, end > systems can use as their global port numbers. > > End systems can obtain information on port numbers > they can use through UPnP or something like that. > > Thus, there is no port number collision at the global > side of the UPnP box. > > Similar mechanism is described in draft-ohta-e2e-nat-00.txt > > Masataka Ohta
