On Jan 6, 2011, at 11:49 PM, Benson Schliesser wrote: > > On Jan 7, 2011, at 12:39 AM, Matthew Kaufman wrote: > >> On 1/6/2011 9:28 PM, Dan Wing wrote: >>> >>> Skype could make it work with direct UDP packets in about 92% of >>> cases, per Google's published direct-to-direct statistic at >>> http://code.google.com/apis/talk/libjingle/important_concepts.html >>> >> If one end is behind a NAT64 and there is no mechanism for discovering the >> NAT64's IPv6 interface prefix and mapping algorithm (and at present there is >> not), there is no way to send IPv6 IP packets from the IPv6-only host to >> IPv4 literal addresses (that is to say, addresses learned via a mechanism >> other than DNS responses synthesized by the DNS64 part of the NAT64 >> "solution") on the IPv4 Internet through said NAT64. >> >> That's the case we're discussing here. >> >> It breaks Skype, Adobe's RTMFP, BitTorrent, ICE-based NAT traversal, etc. >> Even the protocol described in the referenced document, Jingle (as it >> essentially uses ICE) fails. The candidate IPv4 addresses for the end that's >> on the IPv4 Internet (local and STUN-derived) that are delivered over >> Jingle's XMPP path cannot be used by the host that is on IPv6 + NAT64 to >> reach the IPv4 Internet because it has no IPv4 sockets available to it and >> even if it knew that NAT64 existed (which would take a modification to the >> Jingle-based apps) and opened an IPv6 socket it wouldn't know what IPv6 >> address to use to reach the IPv4 host because there's no discovery >> mechanism. If you want we can take this back to the BEHAVE list now. > > To paraphrase what you're saying: stuff that embeds and passes around IPv4 > addresses will break. I'm sorry to say this, but that's just reality. > Embedded IP addresses has always been a Bad Idea (tm) in development and > operations, and I don't think P2P protocols get a pass - building your own > discovery and topology mechanisms don't insulate you from having to use the > underlying network. > No, it hasn't always been a Bad Idea. It has been an idea fraught with peril since the deployment of overloaded NAT in IPv4.
Fortunately, overloaded NAT will hopefully be a thing of the past in IPv6 and we may get a chance to return to a more functional end-to-end model of networking again. > The best chance anybody has, is to build dual-stack support and start using > DNS names rather than IP numbers. Oh, and expect IPv4 to start breaking in > the near future. We're trying to make IPv4 work long enough to survive the > transition, but it's not a good bet for new protocols. > On this, at least we agree. Owen
