[HECnet] PSTHRU.EXE poor-man routing object 123 for VMS on VAX

[Paul Koning]

> On Dec 26, 2021, at 6:04 PM, Thomas DeBellis <tommytimesharing at gmail.com> wrote:
> 
> ...
> Could you elaborate on what 'poor man' routing means, just so I'm sure I have the correct context?  I know that this term existed for 20's route NRT sessions.  It doesn't exist for CTERM.  I don't think I remember seeing it for DAP/FAL/NFT.

"Poor man's routing" as it appears in DECnet means a way to communicate with nodes that are unreachable by the primary protocol mechanisms.  It works by making the user specify an explicit path to the destination (shades of uucp mail).  For example, mail might be addressed to  VAX4::STAR::Goldstein, i.e., the recipient was on node STAR but to get there I'd have to use VAX4 as an intermediate point.

In Phase II, PMR would be used to reach destinations more than one hop away.  With a mix of Phase III and IV, the Phase III nodes would need PMR to reach out of area destinations.  And when "hidden areas" were used to deal with topologies that needed more than 63 areas -- such as DEC's internal network -- PMR would be used to get into or out of a hidden area.

PMR the concept might be implemented in a number of different ways.  Some applications, like MAIL, would provide it as part of the application.  File transfer (DAP protocol) would offer it as a side effect of VMS transparent network access.  And some applications, I think the old network terminal protocols might be an example, would rely on a separate application layer forwarder program.  That would be PMR or PSTHRU, object 123.

PMR as a separate program might originate on TOPS-10 since it has a program by that name that also provides the equivalent service on ANF-10.  Someone posted the source of that recently (a year ago or so, perhaps).  I don't remember ever seeing a protocol spec for the PMR protocol.  Since I have the RSTS source code (it's a program PMR.BAS, in Basic-PLUS) I can reverse engineer such a spec, that's on my "soon" list.  I don't remember if PMR was included with the DECnet kit.  It's a pretty small and simple program.

	paul