--On Monday, 31 December, 2007 10:05 -0800 Barbara Roseman <barbara.roseman@xxxxxxxxx> wrote: > apologies for cross-posting... Which I have deleted on the grounds that most of those lists won't let me post anyway. Feel free to forward if you think it useful. > On 4 February 2008, IANA will add AAAA records for the IPv6 > addresses of the four root servers whose operators have > requested it. A technical analysis of inserting IPv6 records > into the root has been done by a joint working group of > ICANN's Root Server System Advisory Committee and Security and > Stability Advisory Committee, a report of which can be found > at http://www.icann.org/committees/security/sac018.pdf. > Network operators should take whatever steps they feel > appropriate to prepare for the inclusion of AAAA records in > response to root queries. >... While I _strongly_ favor this move, it is often, if not always, useful to examine the applications that use the DNS as well as effects on the DNS itself. Because these changes to the root are likely to facilitate the use of IPv6-native environments (as distinguished of IPv6 systems in clearly IPv4 environments, as the root servers have been to date), they may increase stresses elsewhere. Let me take email as an example of why this is important. Because there are no mail servers associated with the root zone (there is not even a way to express a root-zone email address), there should be no direct effect of these changes. But I think your announcement and comments should anticipate possible indirect effects. When an email address is specified, the domain is interpreted for mail-routing purposes according to rules first laid out in RFC 974, which has been updated in minor ways by RFC 1123 and RFC 2821. RFC 974 defined the MX RR. The data associated with the MX RR is simply a domain name, so MX records raise no issues with IPv6. However, there is also a rule that, if no MX records are present at a particular node, the mail system looks for an A RR at the same node and treats it as if its label appeared with an MX preference of 0. That default does not apply to AAAA records, so it is necessary that operators understand that, if mail systems are to be accessed using IPv6, they MUST have MX records at the relevant nodes. In addition, those MX records should be configured with preferences appropriate to the connectivity of the servers: expecting SMTP-senders to sort out the relative appropriateness and priority from mixed IPv4 and IPv6 addresses at the same preference level is, at best, likely to be operationally unwise. Again, there is no specific root server issue in any of this, but it concerns me that none of the relevant committees or studies appear to have considered the possible applications implications of the change. regards, john _______________________________________________ Ietf@xxxxxxxx https://www1.ietf.org/mailman/listinfo/ietf