HP 3000 Manuals

Configuring Systems for Terminals, Printers, and Other Serial Devices

Typical Network Configurations 


NOTE  If you are configuring X.25 networking capabilities on a HP 3000
      Series 900 computer using host-based network management, use
      Configuring and Managing Host-Based X.25 Links instead of this
      manual to configure DTCs and DTC connections.

      Use this manual for directions on how to perform Dynamic/Automatic
      Configuration or to execute a DTS shutdown or restart.


The DTC makes communication possible across a wide variety of network
configurations.  The DTC provides the following:

   *   Asynchronous connections to HP 9000s and third-party ARPA nodes
       via Telnet.

   *   Access to X.25 networks.

   *   Access to HP 3000s via Telnet from HP9000's or third party ARPA
       nodes.

The networking environment dictates not only the connection options, but
also the type of network managementused.

If users only need access to HP 3000 computers or access from the DTC
ports to HP 9000s and third party ARPA nodes, then each DTC can be
managed from the HP 3000 computer.  This method is known as host-based 
network management. 

If users need access to HP 3000s via Telnet from HP 9000s or third party
ARPA nodes, then each DTC must be managed by an OpenView Windows
Workstation.This method is referred to as PC-based network management. 

If X.25 communicationsis required, then either PC-based Management 
or Host-based X.25 Managercan be used.

Host-Based Management 

When an HP 3000 computer is used to configure and manage DTCs, the system
is using Host-Based Management.  Configuration and control information is
maintained on the host, and downloaded from the host to each of the DTCs
controlled by it.

In the simplest configuration, devices connected through a DTC function
as though a single cable were connecting the device and the computer that
is managing the DTC. With this configuration the DTC would communicate
only with the host from which it is downloaded.

A sample network configuration in which host-based managementis used in
its simplest configuration, is shown in Figure 1-1 .  System A manages
DTC 1 and DTC 2, while System B manages DTC 3.  Terminals connected to
DTC 1 and DTC 2 are able to communicate only with System A, as if a
single connection existed between them.  Likewise, terminals connected to
DTC 3 are only able to establish connections with System B.


          Figure 1-1.  LAN with Host-Based Management 

Host-based management also has the capability to provide the following
types of network connections.  These connections are described later in
this section.

   *   PAD access from terminals connected to PADs to the system that is
       managing the DTC.

   *   X.25 Network Access from other systems connected to a PSN to the
       system that is managing the DTC.

   *   Telnet access from terminals connected to the DTC ports to systems
       running ARPA standard Telnet services.

   *   Multi-System Access to other HP 3000 systems on the LAN.

   *   Back-to-Back Access from one DTC port to another.

PC-Based Management 

When an OpenView Windows Workstation is used to configure and manage
DTCs, the HP 3000 system is using PC-Based Management.  Configuration and
control information for the DTCs is maintained on the OpenView Windows
Workstation running the OpenView DTC Manager software.  This information
is downloaded from the workstation to each of the DTCs being managed.
The OpenView Windows Workstation must reside on the same LAN as the DTCs
which it manages.

When PC-Based Management is used, the DTCs are able to function as
datacommunication servers for multiple computers on the LAN. These
systems can be HP 3000s, HP 9000s, HP 1000s or third-party nodes, which
run the ARPA standard Telnet service.

PC-Based Management provides all of the network connections described in
the following pages.

PAD Access 

DTCs can optionally contain up to three DTC/X.25 Network Access cards.
DTC/ X.25 Network Access cardsconnect devices to computers over a Packet
Switching Network 
(PSN), by using a private or publicPAD.

A PAD, or Packet Assembler/Disassembler, is a device that converts
asynchronous character streamsinto packets that can be transmitted over a
PSN. 
Supported devices attached to the DTC can be remotely connected using a
PAD.

Figure 1-2  shows PAD access to HP 3000 and other computers using a
DTC equipped with the DTC/X.25 Network Access card.  Note that only
terminals are connected to the public PAD. This is because devices that
are opened using the software, such as serial printers, must be connected
to a private PAD and must be permanently associated with a reserved
logical device (ldev) number on the MPE/ iX computer that accesses them.


          Figure 1-2.  DTC/X.25 Network Access for a PAD 

X.25 Network Access 

X.25 iX System Access,when used in conjunction with DTC/X.25 Network
Access,allows you to establish a DTC/X.25 iX Network Access Link,thus
connecting an HP 3000 computer to a public or private X.25 PSN. The X.25
network protocol processing is done by the DTC/X.25 Network Access card
installed in the DTC. If PC-based management is used, then multiple HP
3000s can share the same X.25 network connection.  If Host-based
management is used, then X.25 access is limited to the HP 3000 that is
managing the DTC.

Figure 1-3  shows a Wide Area Network 
(WAN) consisting of two DTCs joined by an X.25 PSN. Both DTCs must
include at least one DTC equipped with at least one DTC/X.25 Network
Access card.  The DTCs can be managed by either OpenView Windows
Workstationsor by the host system.


          Figure 1-3.  DTC/X.25 iX Network Access Link 

Telnet/iX Access 

Telnet/iXprovides connections to MPE systems from terminals connected to
systems running ARPA standard Telnet services.  Telnet/iX includes a
Telnet Access Card(TAC) that resides in the DTC 48 or DTC 72MX and
provides protocol conversion between Telnet and AFCP. Equivalent
functionality is provided by the Telnet Express Server 
(HP2344A).


NOTE  A DTC 48 cannot contain both a TAC and an X.25 card.


Figure 1-4  shows a terminal user connected to an ARPA node and using
the Telnet service to access an HP 3000 Series 900.  The TAC card in the
DTC converts the Telnet traffic into TIO traffic for the MPE system.


          Figure 1-4.  Telnet/iX Access 

Multi-System Access 

Figure 1-5  shows a sample network configuration.  The terminals
connected to DTC 1 are configured so that they are able to establish
connections to either System A or System B through the DTC Switching User 
Interface.Output devices connected to DTC 1, such as serial printers or
plotters, are configured so that they can be opened using the software
from either host.  Note the presence of the OpenView Windows Workstation
on the same LAN with the computers and DTC 1.


          Figure 1-5.  DTC Switching 

Back-to-Back Access 

By arranging DTCs and DTC terminal connections in a special way, terminal
users can establish communications with an MPE V computer.  This is
referred to as back-to-back access. 

Figure 1-6  shows two DTCs in a simple back-to-back configuration.
DTC 1 has terminals connected to it.  DTC 2 is connected through one of
its ports to the Advanced Terminal Processor (ATP) card in the MPE V
computer.  A terminal user connected through DTC 1 is able to establish a
communications link to the MPE V system by going through DTC 2.  Note
that the OpenView Windows Workstation is on the same LAN as the DTCs
involved in the back-to-back configuration.


          Figure 1-6.  DTC Connection to MPE V Host 

MPE/iX 5.5 Documentation