Re: SIP now IPv6

[Dave Crocker <[e-mail]>]

HWB, et al.,

Always interesting to see straightforward engineering work become
politicized.

But since the discussion has finally gotten into the realm of technical
options, I'd like to suggest that the IP version field is _exactly_ the
right place to mark the difference, unless there is strong evidence that
it truly isn't viable, technically.  

The protocol is trying to run on top of all the existing IPv4 sub-network
support, e.g., Arp.  The protocol is, in fact, a technical delta of
v4.  The service interface to the upper layers is also a straight delta.

In other words, the damn thing really is a variant of IPv4.  So, use of
the IP version number field makes sense.

If this turns out to break existing implementations -- assuming that
SIP-as-IPv6 shows up in its pure, unencapsulated form at IPv4-only
systems -- then I agree this should be rethought.

But if we are attempting to develop a running system, then every
piece that is different from the intended final form leaves us open to
the charge of doing unrealistic testing or of creating problems that do
not apply to the final system.

Dave