RE: 3gpp-analysis-05: Use of NAT-PT in IPv6 UE -> IPv4 node

[Pekka Savola <pekkas@netcore.fi>]

Comments to a couple of remaining points only..

On Mon, 22 Sep 2003 juha.wiljakka@nokia.com wrote:
>  JW: I think that a general recommendation for dual stack UEs in the
> near future is a rational one. At least that seems to be the natural 
> step after IPv4-only UEs. But we should also encourage manufacturers 
> to make dual stack UEs instead of v4-only UEs! :-)

Right.

>  2) the use of specific-purpose protocol relays (e.g., IPv6<->IPv4 
> TCP relay configured for a couple of ports only [TRT]) or application 
> proxies (e.g., HTTP proxy, SMTP relay) in the local network, or
> 
>  JW: How much do we have real life / implementation experience on TRT?

It's implemented at least by *BSD and Linux; keywords: faithd, pTRTd, 
(totd -- not really needed in this context):

http://www.freebsd.org/cgi/man.cgi?query=faith
http://v6web.litech.org/ptrtd/
http://www.vermicelli.pasta.cs.uit.no/ipv6/software.html

We've used it extensively on BSD for many years; it has been used at IETFs
(though not for this specific purpose) some time ago repeatedly, etc.

This is certainly not the only way to do it though.  Realistically, the
real life experience may be a bit lacking (I haven't heard of much bad
news) -- or it could be that it just plain Works :-)

Definitely something worth exploring a bit more, I think.

>  3) the use of specific-purpose mechanisms (as described above in 2) in 
> the foreign network; these are indistinguishable from the IPv6-enabled 
> services from the IPv6 UE's perspective, and is not discussed further 
> here.
> 
> The use of generic-purpose translators (such as NAT-PT) is not recommended 
> [NATPTappl]; appendix A lists some 3GPP-specific issues related to the use 
> of translators.
> 
>  JW: In my opinion, NATPTappl will have an important task explaining why you 
> don't want to encourage people using NAT-PT as a generic
> transition mechanism. 

Right..

> I haven't fully understood the big picture. With dual
> stack (and IPv4) we usually have to use v4-NATs anyway. 

But those are an *IPv4* problem.  IPv6 is supposed to be better ;-)

> Just a question: if I say
> that the evilness of NA(P)T is X, how evil would you then say NA(P)T-PT is (compared
> to X)?

A good question.

My view on this: if we transfer the evils of NA(P)T to NA(P)T-PT 
and, moreover, advocate its use, we've actually done a *lot* more evil 
than just bearing with current evils, i.e. those we know of NAT.

That is, we'd be propagating the evils of NAT into IPv6.  That seems 
short-sighted, even though it could be seen as one way to move to 
IPv6-only networks fast.  IMHO, it's much, much better to insist on 
"untainted" IPv6.

Else we'll be back in square 1 before too long..

-- 
Pekka Savola                 "You each name yourselves king, yet the
Netcore Oy                    kingdom bleeds."
Systems. Networks. Security. -- George R.R. Martin: A Clash of Kings