Hi Marcelo, George, I agree with Marcelo that v4 hosts should not be modified.George's 1st possibility looks too much like STUN for my taste :-) so I would not adopt it.
But the second possibility is *almost* workable. In Tunnel Mode, the tunnel-internal v4 address can be received from the v4 peer (easy if the peer happens to be a gateway). As to the external v4 address (the only address when using Transport Mode), I don't see how you can get one on a v6-only network. Note that a random address would do just fine here, we have to deal today with the whole world using 192.168.0.1. And IKEv2 may actually not require any changes.
Thanks, Yaron marcelo bagnulo wrote:
Hi Goerge,thanks for the summary, i was planning to do a similar effort myself, but since you have done that already :-)George Tsirtsis escribió:Marcelo et.al., So, I looked into this in a bit more detail. Admittedly I am not a security expert but I do not think you have to be one to figure this out at least to some level. - First in terms of unmodified end nodes: RFC2765 (SIIT) claims that ESP Transport mode can work over it. This appears to be true given the fact that ESP Transport mode as defined in RFC4303 only covers the headers following the ESP header; see diagrams in pages 18/19 of RFC4303. Note, however, that while ESP Transport mode does not cover IP headers, it does cover Transport and higher headers, so it is NOT possible to perform port translation or to do an ALG processing. So SIIT assumes that NO port translation is going on and each IPv6 only node is using all the ports of each IPv4 address available to the SIIT box. This requires as a minimum, one IPv4 address for each IPv6 end node in a concurrent communication session, and it is the reason why NAT-PT had to also exist. I think this conclusively renders "IPSEC over NAT64 for unmodified end nodes" unrealistic. Any disagrees with that?This is my conclusion as well.IPSEc wihtout at least one of the endpoints involved is not possible (note that this is similar to the IPv4NAT, since in IPv4NAt IPSec support endhosts need to be updated as per RFC3948)So i am planning to NOT to include a basic requirement abou any form of IPSec support wihtout endpoint support, ok?I understnad that what you describe above is only for IPsec tunnel mode. there is also transport mode with modified hosts, which i think it would be easier to make it work, don't you think?- Now about modified end nodes: As we discussed before RFC3948 works based on UDP encapsulation which has become the default v4NAT traversal technique. The premise for this type of solution is that by encapsulating the traffic we can limit the effects of translation to the encapsulation header, leaving the inner header untouched. I think this is not sufficient when IPv6-only nodes interact with IPv4-only nodes since no matter what encapsulation we do in the end there is no way for the two peers to form IP headers of the same version and use them as untouched inner headers. This seems like a dead-end but there is an avenue some people seem to want to explore. This would require one of the peers (presumably the IPv6-only side) to be able to put together an IPv4 header and apply ESP style encapsulation, even if it does not run a full IPv4 stack. In this case, at least in theory, the two peers can then form a session based on the same version of IP. I think then there are two possibilities to explore: 1) An IPv6 tunnel is created between the IPv6-only end node and the NAT64 box. The IPv4 session is then encapsulated over it and it is protected by IPSEC as required. This means that the IPv6 end node knows the external IPv4 address of NAT64 box and the port number to use. 2) A UDP/IP tunnel is created end to end ala RFC3968. Of course this means that the IPv6-only node does UDP/IPv6, which is then translated to UDP/IPv4 by NAT64. The IPv4 session is then encapsulated over it and it is protected by IPSEC as required. This means that the source IPv4 address and port numbers used by the IPv6-only node in the inner headers will have to be valid and non-overlapping at the IPv4-only side too. In both of the above cases IKEv2 will still have to be looked at and see if there is any hope of making that work over NAT64. Making this work for incoming communication is of course even harder. In general, both options present serious challenges which if they are overcome something resembling end to end IPSEC could in theory emerge. My personal opinion, for whatever it is worth, is that this is not a good road to go down, but maybe defining something like this in more detail to see how awful it really is, is still useful. We can always discard it later. Maybe there are also other alternatives I am missing here in which case it would be nice to hear about them.My conclusion of this discussion w.r.t. the requirements is that it would be possible to make it work, but this would require modifications of the endpoints, so, i am thinking in a requirement like:IPSec MUST be supported but modifications to the endpoints may be needed. Now, i have a few related questions:- do we need to upgrade btoh endpoints or would it be enough if we just upgrade one? ( I mean, this could change the requieremtn meaning that the solution must support IPSec if only the v6 node is upgraded with special IPSec handling mechanisms) - Is there anything that the NAT64 needs to do in order to make ths support easier? I mean, at least at this point, it seems possible that IPsec traffic will flow through the NAT64 box, so at least is should be possible to do somehting with that traffic. for instace, how does the NAT64 box handles that traffi when NAPT is being performed? Are there any other thing s that the nat64 could do to make life of the endpoints supporting IPSec clearly easier?Regards, marceloRegards GeorgeOn Fri, Mar 28, 2008 at 8:14 PM, marcelo bagnulo <marcelo@it.uc3m.es> wrote:Hi,Another issue that was brought up during the meeting was IPSec support.I have been reading RFC3948 and i have some questions. I understand that if transport mode can work through v4 NATs usingRFC3948 UDP encapsulation and soem other tweaks defined in the RFC, then it is reasonable to expect that the same level of support of support canbe achieved in NAT64. so we could simply add a requirement that NAT64 mechanisms should support the use cases supported by RFC3948. However, i am not so clear about the tunnel mode.In tunnel mode, we have two IP headers and the NAT64 will only translateone of them (by default, if we don't do anything special with it). so, the problem, is that even if the outside IP header is translatedwith the NAT64 box, the inner header remains in the original IP version,so i am wondering if this doesn't present additionla difficulties. The option is to translate both headers, but this again will be different than the IPv4 NAT case, since the inner header in the IPv4 NAT case remains unchanged, while we would be changing it in this case. So i amfinding that the tunnel mode wouldn't be so directly supported using theIPv4 NAT traversal techniques for IPSec. However, i am not an expert on this, so i may get this completelly wrong. any guidance on this would be appreciated Regards, marceloScanned by Check Point Total Security Gateway.