Problems with removing NAT from a network

Matthew Kaufman matthew at
Thu Jan 6 15:32:23 CST 2011

On 1/6/2011 10:07 AM, Cameron Byrne wrote:
> Skype is not defined in an IETF RFC, so saying you need an RFC to move
> forward is bit confusing.
I don't see a disconnect at all. Skype also uses TCP and UDP, which are 
both subjects of RFCs.

That said, it doesn't need to be an RFC... just *a reliable way* of 
discovering the appropriate NAT64 prefix.
>   There are several methods that just work
> today,
Of the methods proposed in the survey draft, only one - the one that 
doesn't require the DNS64 spec or operator to make any changes (making 
an AAAA lookup for something you know only has an A record) - works but 
*only if* the mapping scheme is such that it is possible to successfully 
derive a functional prefix and the scheme from the results of that query.

So in other words, *if* the query results in an AAAA where, by 
inspection, you can guess where you'd need to stuff the IPv4 address 
bits *and* the resulting address causes the "right" NAT64 (if there's 
 >1) to be used, then you're set.
> I am all for standards, but a closed platforms generally find ways to
> progress without or in spite of standards.  Skype is a closed
> platform.
No question. And for all you know we might be working on other ways 
around this problem, but none of them as elegant as a defined 
specification for how to discover the presence of a NAT64 and the mapping.
>> There's lots of other apps that don't work. Skype is just the squeaky wheel
>> because it is so popular.
> Please make a list and let us know.  Otherwise, this is just hand
> waving like the IPv4 literals sites.
I'll start with "peer to peer connectivity using RTMFP in Flash Player" 
and "BitTorrent". Both Flash Player and BitTorrent are fairly popular on 
desktop platforms.

I'm sure there's more.

> My advice to Skype is to come up with a solution to work for IPv6-only
> clients. That is my advice to all apps and all content.  IPv6-only
> clients are an obvious reality in an IPv4 exhausted world.
That's not the problem... the problem is reaching the existing base of 
IPv4 clients from those IPv6-only clients without making Skype relay all 
the traffic via servers somewhere, as I'm sure you know.

> You cannot seriously come to a network operators support mailing list
> and say that the network guys have to keep investing in network tweaks
> while you wait for a standards body to solve a problem for your closed
> non-standard applications.
I've been on this list since approximately the time it was formed, so 
I'm not coming here to ask for something. Just pointing out what will break.

> I also assure you, many mobile operators are pursuing this NAT64 path
> for the same reason I am.
Randy Bush would encourage his competitors to do just as you've done, 
I'm sure.

Matthew Kaufman

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