Re: No Place Left to Hide on Tomorrow's Net?

[Blue Boar <BlueBoar () thievco com>]

der Mouse wrote:
> It's been a while, so I may have this wrong (and it may depend on which
> DECnet Phase we're talking about), but as I recall, it was actually
> that DECnet tried to reach a machine at a MAC address derived directly
> from its DECnet address (the DECnet node number got a fixed set of bits
> prepended to it).  I don't remember exact details, but it was something
> like node 14:711 (binary 001110 1011000111, hex 3ac7 after regrouping)
> being assumed to be at 0a:00:00:01:3a:c7, the 0a:00:00:01 part being
> constant and part of the spec for that phase of DECnet.
>
> Yes, this put them in a part of the MAC address space assigned to DEC,
> but it didn't depend on having a DEC card, just on having one whose MAC
> address could be set by software (these days that's all of them, but
> back in the earlier days it wasn't).  Of course, it also required
> software that knew how to set the MAC, but that was just part of having
> a DECnet stack that could handle that interface.

The Wikipedia entry is decent:
http://en.wikipedia.org/wiki/DECnet
Look under "Phase IV".

"The Ethernet implementation was unusual in that the software changed 
the physical address of the Ethernet interface on the network to 
AA-00-04-00-xx-yy where xx-yy reflected the DECnet network address of 
the host. This allowed router-less LAN operation because the LAN address 
could be deduced from the DECnet address."

I disagree with the "router-less" bit.  Maybe ARP-equivalent-less.

BB
(Who did too much DECNet in the early 90s.)
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