Re: [sipcore] comments on draft-ietf-sipcore-dns-dual-stack-02

[Brett Tate <[e-mail]>]

> The actual recommendation at end of section 4.1 only says:
>
>   The dual-stack client SHOULD perform an A and AAAA record lookup
>   of the domain name and add the respective IPv4/IPv6 addresses to
>   the list of IP addresses to be contacted.
>
> but it doesn't say if A or AAAA should be placed at the beginning
> of the list, end of the list, or scattered randomly.  It probably
> matters, especially if we envision a long list of AAAA and long
> list of A records, and we also envision an outage of one address
> family.

It may or may not matter (although I agree that the draft should provide a
recommendation).  Similarly, this draft may improve or worsen call setup
delays.

The sender doesn't know if the A/AAAA records reflect the same device or
different devices.  If the records reflect the same device and the device is
down, the draft slows down the advancing to the next SRV record.

If a network administrator had been relying upon the "A or AAAA" behavior of
RFC 3263, they might desire DNS changes based upon the draft's change to "A
and AAAA".  If they do not know if the relevant devices behave per the draft
or RFC 3263, they'd likely want to configure things to work adequately for
both behaviors.