Tops-20 6.x supported Phase II, Phase III and Phase IV.  The NI could handle all three whilst the DN20's (DTE's) were limited to Phase II and III.

Columbia was one of the few sites with a DN200 (DEC's RJE solution) and, as I recall, these were only ever Phase II.  The DN200 continued to work in 6.x.

The first 'network' print spooler worked by writing a daemon that pretended to be a DN200 and then defining that 20 as a DN200 on a 20 with no printer.  It took me about an evening to write in 1980, after I looked at DN200 driver code in Galaxy (NURD.MAC)

The router (or DTE driver) code will not allow a Phase IV message over the DTE, but this restriction appears artificial.

The router appears to still have code for Phase II, at least there is commentary and storage for requiring node names for Phase II.

On the 20, DECNET over the CI was absolutely supported.  The sales-droids actually pushed it as a huge plus.  The transfer speeds blew the NI right out of the water.


On 5/17/24 1:14 PM, Paul Koning wrote:

      
On May 17, 2024, at 11:47 AM, Thomas DeBellis <tommytimesharing@gmail.com> wrote:

...
I wouldn't swear to it, but when we were a field test for 6.x, there was some internal documentation on DECnet over the CI.  I think there is still some kind of write up on it, somewhere.
On 5/17/24 11:19 AM, Paul Koning wrote:
It seems quite reasonable except for the fact that CI has such a limited range and station count.  It's just that it wasn't specified in any DNA spec.
I'd be interested in DECnet/20 and DECnet/VMS docs about CI use.

Some skimming of the VMS 4.0 microfiche listings says that yes, CI support is in there, and the CI driver (CNDRIVER.MAR) in the comments refers to Phase III, and speaks of "tributaries".  So it looks like CI was treated like a sort of DMP-11, a multipoint datalink with explicit connection state to each remote station.

I noticed something else interesting while looking over some NETACP listings: the code appears to support Phase II, III, and IV all in one system.  I had no idea anyone had done that before I did in PyDECnet.  Does anyone here have experience with this?  It would be interesting to see how well it works.

	paul

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