Subject: Re: IPv6 networking: Bad news for small biz

From: [email-masked] (Noel Chiappa)
Date: Wed, 4 Apr 2012 22:32:43 -0400 (EDT)

> From: Steven Bellovin <[email-masked]>

    > NAT didn't really exist when the basic shape of v6 was selected.

I didn't use the term "IPv6" deliberately, and I'm not going to get into a
(pointless) debate about it now. However, I want to set the historical
record straight on this specific point, for any future historian who reads
this.

I first heard the idea of NAT at an IAB architectural retreat in California
(ISI maybe), quite a while before SIP (later IPv6) was proposed. I'm not sure
exactly when that meeting was, but I think it was the meeting referred to in
RFC-1287, which would make it January/June 1991 (not sure which one was the
one where I recall Van making his L-NAT presentation - and I'm pretty sure
Paul T had another variant of NAT, S-NAT, to discuss at the same meeting). You
will find (brief) reference to their work in that RFC (published December
1991).

SIP was first proposed in the fall of 1992 (according to a presentation from
Steve - I can't quickly find the earliest SIP drafts on my PC, or online, to
confirm that). In any case, the _idea_ of NAT was around a _long_ time (in
then-Internet time) before SIP was picked for IPv6 in 1994 (well, SIPP as it
was by then, although the basic concept hadn't really changed).

At that point, NAT was already moderately widespread: I recall very
distinctly several people making the point at the IPng directorate meeting
on the last day of the 30th IETF (Toronto, July 1994) that the newly
minted IPv6's _competitor_ was going to be IPv4+NAT, and from all we could
see, the users were going to prefer that instead.

	Noel

---

From: Bob Braden <[email-masked]>
Date: Thu, 05 Apr 2012 08:41:45 -0700

On 4/4/2012 7:32 PM, Noel Chiappa wrote:
>      >  From: Steven Bellovin<[email-masked]>
>

Noel,

This sounds about right.

Perhaps it is a stretch, but I think that that NAT concept owes much to 
Postel's
"Magic Box" ("Multi-LAN Address Resolution", RFC 925, October 1984,
a much under-appreciated RFC.)

Bob Braden

---

From: Brian E Carpenter <[email-masked]>
Date: Thu, 05 Apr 2012 17:05:30 +0100

> a much under-appreciated RFC.)

Isn't that closer to Proxy ARP? RFC 1027 credits RFC 925.

At CERN, we used an unpublished ad hoc NAT mechanism in about 1980
to interconnnect two copies of a homebrew network with absurdly
small addresses. The DECnet Phase IV 'hidden areas' mechanism was
also a widely used NAT-like hack in the 1980s.

   Brian

---

From: [email-masked]
Date: Thu, 05 Apr 2012 15:37:52 -0700 (PDT)

> also a widely used NAT-like hack in the 1980s.

Of course I have no idea of the details of whatever CERN did back in the 80's,
but the bit about hidden areas didn't gibe with my memory so I looked it up
to be sure...

DECnet hidden areas weren't really NAT-like at all. They were simply a set of
addresses in one group of areas that weren't visible across one or more level 1
routers to another group of areas. In order to get to a hidden area in another
group, you had to use explicit multi-hop routing, e.g., assuning STAR is the
gateway between groups and you want to reach a system called XDELTA in the
other group, you have to say STAR::XDELTA:: instead of just XDELTA::. (I
believe both STAR and XDELTA were actual system names on Digital's large Phase
IV network, chosen because "star" was the code name for the original VAX-11/780
and "xdelta" was the name of the kernel debugger.)

There are plenty of parallels to this in email, including UUCP routing (a!b!c),
percent-hack routing (c%b@a), source routing (@a:c@b), and mixed routing
(b!c@a). (Note that this covers four of the six available permutations - I'd be
curious to know if anyone has an example of either b-a-c or c-a-b order being
used anywhere.)

In fact the same term was used to refer to this trick in both DECnet Phase
IV and email: Poor Man's Routing (PMR).

NAT would be a lot less popular than it is if explicit routing was needed on
all the end systems to make it work. But of course it doesn't work like that.

				Ned

---

From: Brian E Carpenter <[email-masked]>
Date: Fri, 06 Apr 2012 08:01:47 +0100

> Of course I have no idea of the details of whatever CERN did back in the 80's,

I can't remember the details myself, despite having designed it with
a colleague, but it included rewriting packets in the router-equivalent
boxes that connected two networks together. No special claim to fame -
the point is that NAT as it emerged in the Internet was not really
a surprise.

> routers to another group of areas. 

Yes, that's true, but the similarity is that certain addresses became
ambiguous and you had to use a hack to overcome the ambiguity. The hack
was different, as you say.

    Brian

In order to get to a hidden area in another