On 2012-04-05 23:37, Ned Freed wrote:
>> 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 At CERN, we used an unpublished ad hoc NAT mechanism in about 1980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.
>
> 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.
> 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.
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
> 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
>