[jdev] IPv6 readyness?

Tony Finch dot at dotat.at
Fri Apr 18 05:45:51 CDT 2008


On Fri, 18 Apr 2008, Dave Cridland wrote:
>
> Within SMTP, yes - the networking of SMTP is very similar to XMPP.

Except that SMTP has relays but XMPP does not. So in SMTP you can
get service from some third party to relay between the IPv4-only and
IPv6-only worlds. There's no equivalent for XMPP.

> But I think we can probably assume that by the time there are IPv6-only
> servers, IPv6 will be commonplace. Most assumptions are that servers will
> remain dual-stack for a considerable time - clients are far more likely to end
> up IPv6-only.

If you have roaming clients that are likely to end up on 4-only and 6-only
networks then you need a dual-stack server.

> The more interesting problem (which Tony Finch pointed out a while back) is
> that on a SRV lookup, you get the A/AAAA records "for free" in the additional
> section. But if you only get one or other, you can't assume that the other
> doesn't exist. So if you get only A, that doesn't mean that there's no IPv6
> address.

This just requires a bit of care from the server programmer. It isn't a
problem for server admins.

The other thing you need to consider on a v6-only site is how you handle
DNS. Fortunately this is quite easy: you just need an off-site dual-stack
secondary that you can point an NS record at, and another that you can
point bind's dual-stack-servers option at for handling recursive queries
to v4-only NS targets.

Tony.
-- 
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