On Dec 13, 2014, at 10:36 PM, Christian Huitema <huitema@xxxxxxxxxxxxx> wrote: > PCP MAP would work, if well implemented. But many home routers do not support PCP yet, and many applications > work better on their "preferred" port. Of course, all that can be fixed with sufficient effort, but it might be simpler > for the applications to just go to IPv6. Also, 6346 mentions deployment directly to devices like cell phones, > and there is no PCP there. > > I understand that a big motivation of A+P is to avoid Carrier Grade NAT, and I sympathize with that. But I can see some > interesting trouble ahead... Hm, I see your point, and I agree that it will be easier for apps to go to IPv6, at least in principal (availability of IPv6 is still a problem in many situations). However, even if apps go to IPv6, there is significant utility in using PCP, particularly in situations where the HG may have a firewall with a default block policy for incoming connections. So I don't really think there's any reason to separate the two things. Really, apps should support IPv6, and they should support PCP. And home gateways should support it as well; it's frustrating that at present there is no good PCP implementation for OpenWRT, for example. The mobile/PCP intersection is interesting--I haven't seen any exploration of that yet.