Technical data

• A workstation that has the X Window System software installed and configured
• A PC running Windows or Windows NT and some X Window System software,
such as eXcursion or Exceed
The X Display Manager (XDM) is an X client that manages the login process of
a user’s X window session. XDM is responsible for displaying a login screen on a
display specified by an X server, establishing an X window session, and running
scripts that start other X clients. When the user logs out of the X session, XDM
is responsible for closing all connections and for resetting the terminal for the
next user session.
An earlier version of XDM had limitations that were resolved with the introduction
of the XDM Control Protocol (XDMCP). Before XDMCP, XDM used the XSERVERS
file to keep track of the X terminals for which it managed the login process. At
startup, XDM initialized all X terminals listed in the XSERVERS file. If the X
terminal was turned off and then turned on again, XDM had no way of knowing
that a new login process should be initiated at the X terminal. To reinitialize the X
terminal, the XDM process had to be restarted. XDMCP solves this problem.
With XDMCP, XDM can listen for management requests from X terminals as well
as use the XSERVERS file for the X terminals that were not XDMCP compatible.
(Most X terminals today are XDMCP compatible.)
The TCP/IP Services implementation of XDM is based on the X11R6.1 release
from X Consortium.
7.5 DECnet over TCP/IP
TCP/IP Services software includes the PATHWORKS Internet Protocol (PWIP)
driver and the PWIP ancillary control process (PWIP_ACP). The PWIP driver
allows OpenVMS systems that are running DECnet over TCP/IP, which is included
with the DECnet-Plus for OpenVMS Version 6.0 and later software.
In a multiprotocol networking environment, DECnet-Plus enables OSI and DECnet
applications to run over an IP network backbone. The OSI over TCP/IP (using RFC
1006) software enables OSI applications such as FTAM, Virtual Terminal, and
X.400 to run over TCP/IP. The DECnet over TCP/IP (using RFC 1859) feature
allows traditional DECnet applications to run over TCP/IP. Examples of traditional
DECnet applications are
mail, cterm,
and
fal
.
With RFC 1006 and RFC 1859, OSI and DECnet applications can accept IP names
and addresses. These names and addresses are translated by BIND servers. The
DECnet and OSI applications include those supplied by Compaq, third-party
applications, and user-written applications.
RFC 1006 is a standard of the Internet community. It defines how to implement
ISO 8073 Class 0 on top of TCP. Hosts that implement RFC 1006 are expected to
listenonTCPport102.
DECnet over TCP/IP uses RFC 1859, which defines how to implement ISO 8073,
Transport Class 2 Non-Use of Explicit Flow Control on Top of TCP (RFC 1006
Extension). Hosts that implement RFC 1859 are required to listen on well-known
TCP port 399.
_____________________ Decision Point _____________________
Use DECnet over TCP/IP if you need to:
Link DECnet nodes using TCP/IP.
7–6 Connectivity Services