Reviving ARPAnet

[Charles Anthony]

On Thu, Jan 18, 2018 at 10:27 AM, Noel Chiappa via cctalk <
cctalk at classiccmp.org> wrote:

>     > From: Grant Taylor
>
>
> The ARPANET supported several different kinds of interfaces between the
> IMPs
> (the switching nodes in the ARPANET) and hosts, but the 'usual' one was
> either 'Local Host' (LH) or 'Distant Host' (DH) which were _basically_
> identical except at the very lowest level - LH was TTL, and DH was
> differential pair.
>
> Those interfaces were a custom bit-serial thing with a handshake (with
> "there's-your-bit", "ready-for-next-bit" lines, etc); see BBN Report #1822:
>
>
And an "end-of-packet" bit.


>   http://www.bitsavers.org/pdf/bbn/imp/BBN1822_Jan1976.pdf
>
> So the "ARPANET interface" in the host is a piece of custom hardware (some
> were DMA; I also used one which was interrupt per byte) which went on the
> host, which talked 1822 (as it was called), of either the DH or LH physical
> form.
>
>
>
>     > Do the necessary emulators support the ARPANET interface?
>
> Dunno, but they shouldn't be too hard to add.
>
> The real problem is going to be 'what do you hook the simulated ARPANET
> interfaces up to, and how'? I know they have IMP code running in
> simulators:
>
>   http://mailman.trailing-edge.com/pipermail/simh/2013-
> November/007672.html
>
> but I dunno how one would hook _that_ simulation up to a simulated host
> running a simulated ARPANET interface.
>
>
The IMP emulator emulates the DH/LH interface with UDP packets. I wired up
the dps8/m emulator to the IMP emulator, but I don't have the ARPAnet stack
for Multics, so it's just packets.

-- Charles