4.2bsd gatewaying

[CERF at USC-ISI.ARPA]

Ron,

Along time ago, BBN had to introduce similar fire walls between their
commercial Telenet system and the ARPANET (you may recall that BBN started
Telenet and sold it to GTE later). They were concerned at that time with
TOPS-20 or Tenex systems which were on both Telenet and ARPANET.

At that time there was no IP and no host gateway, so they only had to
block user access from one net via the host to the other.

What happens if you use two hardware interfaces (one to the local net and
one to the Milnet) and two copies of IP. The two copies of IP need not
know about each other's existence. Users of the IP layer would need to
know to route (select) IP services based on destination network.

Sounds awful, but it looks to me as if you need to bifurcate the
view of the world at about the gateway level if you are to maintain
the fiction that your machine is a host on two system which is
not, accidently, a gateway between them as well.

As to actual code availability to achieve this - I dunno.

Vint