What is DECnet over TCP/IP ?
DECnet over TCP/IP provides a means for DECnet applications
to use TCP/IP as a network service rather than the traditional
DECnet network service.
It allows the coexistence of DECnet and TCP/IP applications
in your network , so that:
- You can use older DECnet applications as is no
rewriting or re-engineering is needed to support a new network
- You can write new IP applications for
e-business and the Internet.
- You can maintain a single network backbone for cost savings
and ease of network management.
DECnet over TCP/IP is based on standards defined in the following
- RFC 1006 - OSI Applications over TCP/IP
- RFC 1859 - DECnet over TCP/IP
- RFC 2126 - OSI and DECnet Applications over IPv4 and IPv6
Q: Who can benefit ?
A: Anyone running DECnet applications can take advantage of DECnet
over TCP/IP. This includes just about any installation running OpenVMS.
Q: What are the benefits ?
A: DECnet over TCP/IP allows you to balance the demands of existing
application users with the pressure to reduce costs by simplifying
- A single network backbone, transmitting multiple network protocols
(including NSP, OSI, and TCP) can provide cost savings and simplify
- DECnet over TCP/IP enables the coexistence of both DECnet and
TCP/IP applications on systems connected by a single network backbone
DECnet over TCP/IP makes it possible to combine separate DECnet
networks/LANs without renumbering the network nodes. For example,
if two companies merge, and both companies have systems with the
same node addresses (e.g., Company A has nodes 10.1 through 10.5,
and Company B has nodes 10.1 through 10.10), an IP link between
the two ensures that the node addresses are unique to the LAN, no
costly (and confusing) re-addressing of the nodes is required.
DECnet over TCP/IP offers protection from random intrusions from
Internet users. [TCP/IP based intranets need to actively secure
the intranet from intrusions. DECnet implements security of the
system you are connecting to: TCP/IP security varies by application
(e.g., telnet, ftp, etc.)]
Q: Doesn't it require extra network resources ?
A: DECnet over TCP/IP is not just another tunnel or gateway between
one protocol and another. Unlike tunnels, there is no duplication
of function between the upper layer applications and the lower TCP
and IP layers. When using DECnet over TCP/IP, the flow-control
and error-recovery mechanisms are those of TCP and underlying IP.
As a consequence, there is no inherent performance overhead with
running DECnet over TCP/IP, unlike that which is found in tunneling
Equally important, DECnet over TCP/IP does not define a gateway
between the DECnet and TCP/IP worlds. Systems running DECnet over
TCP/IP are still DECnet systems ; they just use TCP/IP (along with
other protocols) for DECnet communications, while not interfering
with "pure" TCP/IP communication from TCP/IP applications on the
Q: What software do I need? What does it cost?
A: You likely already have installed the software that you need.
DECnet over TCP/IP requires that you have a supported version of
DECnet-Plus for OpenVMS and a supported version of an industry standard
TCP/IP stack, like Compaq TCP/IP Services for OpenVMS. Licenses
for both DECnet-Plus for OpenVMS and Compaq's TCP/IP Services for
OpenVMS are included in Compaq's Enterprise Integration Package
(EIP), which ships with Compaq OpenVMS AlphaServer systems. The
products ship on Compaq's Layered Product Consolidated Distribution
and also with the OpenVMS Operating System CD.
There are no new/additional costs, no new product licenses or
media to purchase or install.
Q: How do I use DECnet over TCP/IP?
A: In order to use DECnet over TCP/IP, you must have installed
DECnet-Plus and TCP/IP Services for OpenVMS. In addition, you must
enable the PWIP driver as part of the TCP/IP Configuration. Product
specific installation instructions are in the appropriate product
The decision to use DECnet or IP as the transport is based on
the remote node address supplied either by the application or the
user. You can force a DECnet connection if you supply a DECnet node
address or a DECnet fullname; you can force a TCP/IP connection
if you supply an IP node address or TCP/IP fullname.
For example, the following will result in using the DECnet transport
SET HOST 10.6
SET HOST LOCAL:.NODE1
The following will result in using the TCP/IP transport
SET HOST 10.18.124.14
SET HOST NODE1.ABS.CKJ.COM
Note that in both cases you are using the DECnet "SET HOST" command.
If you (or the DECnet application) uses a DECnet synonym (also
known as an alias and DECnet short name), DECnet session control
will select the transport based on how the network manager configured
the system. For example, SET HOST NODE1 will force a name to address
lookup in DECnet session control. If the lookup returns a DECnet
address, the DECnet transport will be used; if the lookup returns
an IP address, the TCP/IP transport will be used.
Details on how to configure name resolution in DECnet session
control are described in the DECnet-Plus Network Management documentation.
Q: Where can I find out more about DECnet over TCP/IP
A: Go to the the following online resources:
» DECnet-Plus for OpenVMS Applications Installation and Advanced Configuration Manual
» DECnet-Plus for OpenVMS Network Management
» DECnet-Plus Planning Guide
» TCP/IP Services for OpenVMS Installation Guide