Re: [Sipping] Question on draft-ietf-sipping-v6-transition-07

["Vijay K. Gurbani" <[e-mail]>]

Elwell, John wrote:
> " 1.  In some cases, especially those dealing with third party call 
> control (see Section 4.2 of [12]), there arises a need to specify the
> IPv6 equivalent of the IPv4 unspecified address (0.0.0.0) in the SDP
> offer.  For this, IPv6 implementations MUST use a domain name within
> the .invalid DNS top-level domain instead of using the IPv6
> unspecified address (i.e., ::)."
> 
> Can somebody recall the reason for this? Both "0.0.0.0" and "::" mean
> "unspecified" in their respective IP versions.

John: Right; so I went back to my email archives to when
Gonzalo and I had a conversation about this (on April 27, 2006.)

We favored an .invalid over :: because the Application folks had
indicated this to be their preference in the past.  For IPv4,
0.0.0.0 was supported for backwards compatibility, but it appears
that a move to IPv6 can be handled cleanly with using only .invalid
instead of having two alternative solutions.

Thanks,

- vijay
-- 
Vijay K. Gurbani, Bell Laboratories, Alcatel-Lucent
1960 Lucent Lane, Rm. 9C-533, Naperville, Illinois 60566 (USA)
Email: vkg@{alcatel-lucent.com,bell-labs.com,acm.org}
Web:   http://ect.bell-labs.com/who/vkg/