Re: [v4v6interim] [46translation] [BEHAVE] Proposal for new BEHAVE charter

[Margaret Wasserman <[e-mail]>]

On Oct 20, 2008, at 6:58 AM, Rémi Denis-Courmont wrote:
> I share your analysis that, _assuming_ we have NAT66, it should be
> transport-agnostic. IPv6 has a large enough address space, and we are
> painfully aware of the problems of transport-dependent NAT(44).
>
> However, when I look at the reasons for deploying NAT:
> 1/ address space shortage
> 2/ inbound firewalling
> 3/ topology hiding
> 4/ prefix delegation "bypass"
>
> (1) is a non-issue for IPv6. (2) is solved with stateful firewalling  
> and does
> not require NAT. 1:1 NAT fails to solve (3) as it does hide the  
> subnetting
> scheme, but fails to hide individual hosts. This leaves only (4).  
> Did I miss
> anything?

There are many enterprise networks that have plenty of IPv4 address  
space available to them, but choose to use NAT44 as part of their  
network architecture.  The most common reason I've heard for using  
NAT44 in these cases is to separate an enterprise's internal address  
block from the IP address block provided by their ISP, which I think  
is akin to your option (4).  This allows their internal operations to  
remain stable across ISP renumbering or a decision to change ISP.

There is every reason to believe that these same enterprises will use  
NAT66 for exactly the same reason.  In fact, given that all IPv6  
addresses will be ISP-provided, I'd predict that more, not fewer,  
enterprises will choose to use NAT66 to gain provider independence.

I agree that it would be a good thing to provide a better alternative,  
but we have yet to do so.  I'm also unconvinced that we can convince  
everyone to try the "better" alternative before NAT66 becomes widely  
deployed.

I don't _want_ NAT66 to be deployed any more than the rest of you, but  
I believe it is inevitable.  We may have an opportunity to influence  
how it is implemented and used, but I don't think we can stop it from  
happening.

> I guess only time would tell whether a NAT66 1:1 spec would help  
> prevent such
> the transport-dependent NAT66 being _deployed_. It cannot hurt to  
> write that
> spec, I suppose. In any case, the abomination will be  
> _implemented_ :-( It is
> too natural/easy/tempting.

After the encouraging response from Marcelo, I'm already working on a  
draft...  I should have something out by the -00 deadline, but I  
haven't figured out where to target it yet -- probably it makes more  
sense to propose it as a behave work item than as a v4v6translation  
item, since it doesn't involve any IPv4.  Suggestions are welcome,  
though.

Margaret

>
> -- 
> Rémi Denis-Courmont
> Maemo Software, Nokia Devices R&D
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