Le 2 avr. 2010 à 00:38, Mark Andrews a écrit : >> >>> Indeed, providing end users with native IPv6 will make the problematic >>> transitional techniques obsolete. However, this is not something that >>> content providers such as Yahoo or myself have much influence over. >> >> At least, they should: >> - get native IPv6 addresses >> - make sure they advertise both a native-IPv6 and 6to4 addresses. > > They shouldn't need a 6to4 address. They should however configure > the exit routers to gateway the 6to4 destined traffic onto IPv4.
What you propose: - does guarantee a good path from Yahoo servers to 6to4 clients, you are right - but doesn't guarantee a good path from 6to4 clients to Yahoo servers => it is not sufficient. Without Yahoo 6to4 routers operated by Yahoo, paths from 6to4 clients depend on a 6to4 Relay Router being reachable from them, which is not guaranteed. On the contrary, by operating its own 6to4 Routers (and embedding their IPv4 address in Yahoo-server 6to4 addresses), IPv6 packets always go directly from 6to4-client sites to Yahoo-server sites (encapsulated in IPv4 from client 6to4 router to Yahoo 6to4 router), i.e. without depending on any Relay Router. > ISP's, in general, should be providing 6to4 gateways even if they > are not offering IPv6 native to their customers. They MAY not do it, though (taking obviously "gateways" as meaning, in RFC 3056 and RFC 3964 terminology, "Relay Routers") Reality is that 6to4 guarantees connectivity *between two 6to4 sites* (in RFC 3056, the Simple scenario of section 5.1), but not between 6to4 sites and native-IPv6 sites (the Mixed scenario of section 5.2). Note that RFC 3964 says about "Security Considerations for 6to4" (emphasis added): "There are mainly four classes of potential problem sources: 1. 6to4 routers not being able to identify whether RELAYS are legitimate ... The first is the TOUGHEST PROBLEM, still UNDER RESEARCH." > While CPE equipment > that supports IPv6 is still hard to get, there really is no excuse > for ISP's to not be doing this any longer. Reasons ISPs may have for not providing 6to4 Relay Routers include: - Relay Routers encourage use of 6to4 in scenarios others than those where connectivity is guaranteed, which is bad for IPv6 in general - An ISP 6to4 Relay Router can be used for traffic that concerns none of its customers. - The wish to not depend on a subject under research (the RFC 3964 quotation above). They are all IMHO legitimate. I hope this helps to understand that there are precautions that CAN be taken, and that, this being done, the FUD about IPv6 in general may dissipate faster. Regards, RD _______________________________________________ DNSOP mailing list DNSOP@ietf.org https://www.ietf.org/mailman/listinfo/dnsop
