The DECnet over TCP/IP feature extends the DECnet Phase V
architecture to coexist and communicate with TCP/IP networks. This
feature requires a valid DECnet license and a licensed and installed
TCP/IP product that supports the PATHWORKS Internet Protocol (PWIP)
interface.
You should consider enabling DECnet over TCP/IP for the following
purposes:
Transition from DECnet to TCP/IP.
To move to TCP/IP-based networks gradually based on business need. DECnet
over TCP/IP functionality is designed to be transparent to users.
Coexistence. To run DECnet or OSI applications,
or both, in a TCP/IP-based network.
With DECnet over TCP/IP, you can:
Expand your DECnet network to communicate
over TCP/IP network backbones. DECnet over TCP/IP allows combinations
of naming services (DECdns, large LOCAL file, and DNS/BIND).
Expand the network by joining two existing DECnet
networks without the need to renumber the nodes.
Use IP-only traffic in part or all of the backbone.
With DECnet over TCP/IP, DECnet or OSI applications can run over
the lower levels of the TCP/IP protocol stack and the IP network
backbone.
Enable the feature on a node-to-node basis or throughout
the entire network.
The DECnet over TCP/IP functionality uses TCP/IP to form a
logical link between DECnet nodes. It uses the PATHWORKS IP Driver
to interface with TCP. DECnet applications run transparently between
DECnet nodes connected by TCP/IP. Users on those DECnet nodes can
connect to each other using DECnet node synonyms or IP fullnames.
For example:
$ SET HOST SYSABC
$ SET HOST SYSABC.boston.acme.com
$ SET HOST 16.12.42.19
To enable DECnet over TCP/IP on your system, you must do the
following primary tasks:
Install and configure DECnet-Plus
on the system. When you run the NET$CONFIGURE procedure using the advanced
option, you must specify at least the Domain directory service in
your list of directory services. Also, you need to answer YES to
the question "Configure the OSI transport or run over TCP/IP?"
Install and configure TCP/IP Services on the system. When you run the TCPIP$CONFIG configuration procedure, enable
the PWIP driver to form a bridge between DECnet-Plus and TCP/IP
Services software. The PWIP driver is listed as Option 1 on the Optional
Components menu.
For detailed information about enabling and using DECnet over
TCP/IP, refer to the DECnet-Plus for OpenVMS Applications Installation and Advanced Configuration and the DECnet-Plus for OpenVMS Network Management manuals.
HP OpenVMS System Manager's Manual, Volume 2:... 
Network Considerations
