David Goodwin wrote:

In a few days I will finally get my hands on a machine to learn
OpenVMS on (an AlphaServer 1200). Before then I must figure out what
TCP/IP stack to use. I know almost nothing about any of them and dont
know very much about how to use OpenVMS in general.

Multinet and TCPware seem to be made by the same company and their
website pages seem almost identical. I assume there must be some major
difference between them - I dont see any reason why one company would
make two seemingly identical products for the same platform.

Could anyone tell me which TCP/IP stack I want to use and what are the
major differences between them?

Well, Process Software's products are bit more straight-forward to manage,
though the management interface takes a bit of learning. The code is functional
and robust and provides 100% compatibility with .EXEs LINKed against the UCX

UCX (now known as "TCP/IP Services for OpenVMS" - hence the preference for the
shorter, if older, name) has rather a bizarre management interface and is really
intended to be more consistent with the UN*X approach to management of the IP

UCX also has a major "gotcha": when multiple interfaces are assigned to the same
subnet the loss of any one interface will render the entire subnet unusable.
This is due to a UCX feature where in it "round robins" the outgoing traffic
among the available interfaces on a subnet. This feature cannot be defeated, and
although most folks recommend "failSAFE-IP" as a remedy, this does not work
because UCX cannot properly detect connectivity failure above the physical

Performance wise, ...

PSC's products still use Direct I/O for the network. Hence, each network I/O
generates an interrupt. This can result in CPU saturation in extreme cases,
mostly with huge databases and other applications with tens of thousands of
active connections.

UCX uses Buffered I/O for the network resulting in more CPU time being available
in User Mode; hence, more actual work gets done than when the CPUs are busy
performing interrupt service.

It depends on what you need: raw performance or manageability and functionality.

Tough call, at best.

David J Dachtera
dba DJE Systems

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