Re: Follow-up work on NAT-PT - a new approach

[John Curran <jcurran@mail.com>]

At 11:25 AM +1300 11/9/07, Brian E Carpenter wrote:
>I would envisage a similar approach for an ISP supporting
>SOHO subscribers - that really isn't much different from
>a campus network. The ISP will need dual-stack mail servers,
>for example. Anyone providing services to the public will need
>a dual stack, for that matter, if they want to be accessible.

At some point, ISP's will: 1) Be unable to readily obtain additional
IPv4 address space, 2) Want to keep growing, and 3) Want a
method for connecting up customers via IPv6-only which provides
some semblance of full Internet connectivity (including backward
reachability to IPv4 destinations).

From the ISP point of view, some of the key requirements are:

 - Has to require a minimal amount of special per-site
   (or per-site-host) configuration in order to provide
   the connectivity to Internet IPv4-only sites.

 - Allow for sharing of some IPv4 space that the ISP
   has set aside for such purposes.

 - Allow implementation of the same "site" policies
   (such as port-based firewall filters) on the IPv4
   backward-compatible connectivity that customers
   use today to provide nominal security.

Contrary to what a lot of folks think, I don't think that the
backwards-compatibility IPv4 connectivity really needs to
be general purpose, or application friendly, or support a
truly end2end model.   While NAT-PR is indeed imperfect
(as documented in RFC4966), it still provides minimal
backwards connectivity that is going to be desperately
needed for many providers.

>However, for the residual cases, it's precisely because
>of the issues with NAT-PT that I've just started working
>on SHANTI. Whether that's of value is for the community
>to say.

If there's a way to improve the resulting connectivity
without create a raft of customer configuration and
support issues, it's probably of value to the community.

/John