Deploying IPv6

A couple of quick developments on the IETF front.

First is http://www.ietf.org/internet-drafts/draft-yan-ipv6-ra-dns-00.txt - a recent draft specifying how autoconfigured nodes should do dynamic DNS updates. The most interesting thing here is that hosts can explicitly ask the router to do it for them, which should be interesting to get right; the router’ll have to keep a lot of state on large networks. But it’s another piece of the puzzle getting slotted into place.

Second is ftp://ftp.rfc-editor.org/in-notes/rfc3974.txt, an informational RFC on operating dual-stack SMTP servers. The core of the document is a description of the algorithm that should be used when dual-stack SMTP servers send mail. Since adding quad A records to MX records essentially adds an extra “dimension” to the MTA resolution process, I would recommend reading it so you get a better idea of how things work in the new world. In particular, quad A destinations are preferred over A destinations, but only within a set of MX records that have the same preferences. This means that it’s not possible to set up an experimental high-preference quad A MTA which then acts as a hoover for all of your mail, which is good, but also means it’s difficult for non-dual-stack mail servers with a low MX preference to be worked around. (One option is to put an IPv6-only server at an even-lower preference.)

Anyway, is it just me, or should we rework and reword the algorithm and the terms high- and low- preference MX, so we don’t have this running ambiguity in our heads about what we mean every time we talk about MX values?

Niall