[Simh] VMS/VDE: Almost there

[Jeremy Begg]

Hi,

>DECNET provides host connectivity (like telnet), file transfer (like ftp),
>electronic mail (like smtp+{pop,imap}), data sharing (like nfs), and loosely
>coupled clustering.  Digital actually believed that it should replace all of
>the IP-based protocols, since it was actively engineered instead of being a
>series of experiments (in Digital's view) that grew like Topsy; Digital tried
>very hard to make it a real implementation of the ISO X.400 pipe dream^W^Wstandards.

I'd like to add a couple of comments, speaking a current VMS practitioner
(yes there are a few of us out there, although these days my Linux income
is more reliable!)

Up to and including DECnet-IV, DECnet used only its own proprietary network
transport protocols operating over Ethernet and a some forms of serial
interface.  (And note that VMScluster's own protocol is not DECnet, nor is
LAT.)

DECnet-V, aka DECnet-OSI, was DEC's attempt to do a complete implementation
of the various OSI X.nnn protocols.  At the time it was introduced, in the
early 1990s I think, it was too big a leap for most customers.  It was just
too unwieldy, and most people stuck with DECnet-IV.

By the end of the century DEC had learned that lesson and DECnet-OSI morphed
into DECnet-Plus which tames some of the OSI management hassles and, more
importantly, allows DECnet applications to run over a TCP/IP network.  In
fact out-of-the box DECnet will use TCP/IP as the transport layer rather
than the proprietary DECnet-NSP (the transport underlying DECnet-IV).

Some of you may be wondering why the ability to run DECnet applications over
IP is important.  Quite apart from some VMS applications being written to
use the DECnet API for node-to-node communication, the great thing about
DECnet is that the syntax for specifying a remote node is part of the
standard VMS filename syntax.  So if I want to (say) edit a file which
happens to be on a remote node, I don't have to log onto that node first:
all I do is specify the nodename or address as part of the filename when I
invoke the editor. This becomes even more powerful when used in conjunction
with VMS logical names, so that the application doesn't have to know or care
that a file it's accessing is not on the local system.

So once you've got SIMH running OpenVMS VAX V7.3 with DECnet-Plus *and*
TCP/IP, you can use your favourite DECnet commands and filesystem utilities
to access other VMS systems (provided they too are using DECnet-Plus with
TCP/IP -- and these days, most should be).

Regards,

        Jeremy Begg

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