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OpenVMS and DECnet have provided customers excellent service
for over 25 years.
OpenVMS and DECnet will continue to provide a viable platform
running on state-of-the-art systems for years more to come.
Customers World Wide have been consistently pleased with its
reliability, robustness, security, and performance. OpenVMS
customers continue to use DECnet to perform demanding tasks
at installations in a variety of vertical markets.
While all the above are compelling reasons to
stay with DECnet, we see migrating from DECnet to TCP/IP for
networked applications as a viable option that should be entertained
by our loyal customer base.
We have found many users who have demonstrated
success by performing an orderly and cost-effective DECnet
phase out, replacing it with TCP/IP, the industry networking
standard.
Customers have retained the benefits of OpenVMS while integrating
TCP/IP as their primary interconnect strategy.
In general, DECnet and TCP/IP offer the same basic services to
applications and the operating system. Both offer a QIO interface
that applications may use to communicate across the network. Both
offer high-level utilities for file transfer, email, and remote
terminal access (among others).
In contrast, TCP/IP provides a stream or byte oriented protocol,
while DECnet provides a packet oriented protocol. DECnet is more
closely coupled to the file system offering additional file system
related services transparently to the application via either file
system calls or I/O operations provided by a particular language.
TCP/IP is not quite as closely coupled in general, but is fairly
transparent when using the C programming language. TCP/IP also provides
an additional programming interface that is not available with DECnet.
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So why is there a need for change? While the maturity of DECnet
provides many benefits such as high reliability and stability there
are compelling reasons to migrate to IP:
- DECnet applications can only communicate
with other DECnet applications. They cannot communicate
and interoperate with TCP/IP applications on the same or
other systems.
- There is a large installed base of third
party and open source applications that run IP and it gets
larger with each day.
- Enterprises can save money and simplify their
networks by mandating that only IP will be supported. Why
support multiprotocols?
- Personnel with IP management, administrative,
and development skills are more available today because
it is an industry standard.
- TCP/IP, with all its services, programming
interfaces, etc., provides the industry standard for networking,
and many users are choosing IP to replace proprietary protocols.
- While routers may handle both DECnet and
IP, it will be possible in some environments to eliminate
duplicate circuits, wiring, and networking equipment, and
administrative costs can be reduced, as DECnet routing requirements
are eliminated.
- HP TCP/IP for OpenVMS has been engineered
by OpenVMS engineering. The very same engineering expertise
that brought you DECnet providing you a migration alternative
that has been extensively qualified and tested with the
OpenVMS operating system.
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We see three primary scenarios available to our users of DECnet:
| DECnet
Islands |
This is
a passive strategy to allow OpenVMS and DECnet applications
to continue in operation without significant upgrades and to
use TCP/IP for new systems and applications. This approach will,
over time create smaller and smaller DECnet island LAN's. |
| DECnet
over TCP/IP Coexistence with DECnet over TCP/IP |
Switch to DECnet over
TCP/IP, allowing wide area operation in the WAN's IP environment.
Running DECnet over IP means that DECnet uses the TCP/IP transport
stack. This switch away from native DECnet does not require
application changes and will allow DECnet applications to continue
to operate in the enterprise, but it will not allow them to
interoperate with other TCP/IP applications. |
| Full TCP/IP Migration |
This is a proactive strategy to eliminate
all DECnet usage, even within LANs, and is the most complex
of the alternatives. The most significant tasks are upgrading
or replacing all of the custom and third party applications
in the application portfolio that use DECnet QIO System Services,
replacing QIO System Services usage with sockets. This can require
reprogramming as well as development costs. The reprogramming
task is complex, using a stream-oriented programming model rather
than DECnet packets. |
It is also not uncommon for the migration path to go from DECnet
to DECnet over IP to full TCP/IP implementation and can be recommended.
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Each customer is unique and will have unique migration requirements. Some customers will
not want to make intrusive changes to their applications, thus eliminating
the "Complete Migration" option. Some customers may be willing to make application changes,
but will compare the cost of those changes against the cost associated with migrating to an
entirely different application that doesn't have the same migration issues.
Because each application is unique, it's difficult to create a step-by-step procedure
for application modification that will apply to every application.
We have provided IP migration white papers from ArrAy
and EDS to help you better appraise
the implementation issues that you may face in your quest of moving
to IP. Of note are the migration services that can be provided to
your business by both ArrAy and EDS to help you in your implementation
journey. Good luck in you migration efforts!
DECnet Migration Services
from ArrAy and EDS
| Workshops |
Provide information to OpenVMS users about DECnet to TCP/IP migration |
| Assessment |
Work with the customer to determine
goals, requirements, and objectives and to understand
current and future operations |
| Project Planning |
Create a phased
migration schedule, plan resource usage and costs, specify
any hardware and software purchases, training requirements,
and acceptance criteria |
| Technical Specifications |
Define service mapping, application migration techniques, etc. |
| Tools |
Assist in migration and for ongoing use onece the migration is complete |
| Project Execution and Management |
Perform the migration as specified during planning |
| Testing and Acceptance |
Assure that all customer requirements are satisfied |
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