Technical data

Managing Peripheral Devices
8.7 Managing Modems
Table 8–3 Related Modem Documentation
Reference Description
DECnet-Plus for
OpenVMS Network
Management
Explains the use of modems to establish a dynamic asynchronous
DECnet connection between two nodes. Asynchronous DECnet is a
protocol that can operate over a modem datalink.
Compaq TCP/IP
Services for
OpenVMS
Management
Explains the use of modems to establish a serial connection using
the PPP (Alpha only) and SLIP protocols and TCP/IP Services.
OpenVMS Guide to
System Security
Discusses how to maintain the security of DECnet modem
connections and dial-in modem lines.
TCP/IP
Networking on
OpenVMS Systems
Explains the use of PPP on OpenVMS Alpha and OpenVMS VAX to
communicate with remote systems.
OpenVMS System
Management
Utilities Reference
Manual: M–Z
Describes the PPP utiltity and associated commands.
Section 8.6.2 Explains how to configure and manage virtual terminals.
OpenVMS DCL
Dictionary and
online help
The DCL command SET HOST/DTE discusses the use of modems to
connect to a remote system.
The DCL commands CONNECT and DISCONNECT explain how to
set up and disconnect virtual terminals.
Direct and Indirect Connections
Part of the job of configuring a modem to a computer or a terminal is to decide
what type of access the modem will have to your computing environment and
which serial communications ports best meet your requirements.
You can choose to connect a modem directly to a host system, or you can
connect the modem indirectly to an intermediate network server device such
as a DECserver. Explanations of these two types of connections follow.
• Direct connection
A direct connection dedicates the modem to a particular host system. This
reduces the amount of access available to the modem caller, and can reduce to
one the number of systems that you must protect against unauthorized access
through this modem.
This is often the configuration of choice for smaller computing environments,
or for connecting a modem to a single computer or terminal.
• Indirect connection
An indirect connection creates a pool of modems for a variety of computer
systems on the local area network, including servers that communicate with
the host computers using protocols such as LAT and Telnet. This type of
connection makes better use of the available telephone lines but increases
security requirements.
This is often the configuration of choice for larger computing environments.
An indirect connection is commonly used when you use LAT or Telnet
protocols to configure a number of modems, called a modem pool, to share
access to a number of computer systems.
With either type of connection, you cannot use the modem if the host or the server
the modem is connected to is not operational.
8–26 Managing Peripheral Devices