Typical Network Configurations

• 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.

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 management is used in its simplest configuration, is shown in Figure 1-1 “LAN with Host-Based Management”. 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.

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 cards connect devices to computers over a Packet Switching Network (PSN), by using a private or public PAD.

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

Figure 1-2 “DTC/X.25 Network Access for a PAD” 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 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 “DTC/X.25 iX Network Access Link” 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 Workstations or by the host system.

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

Telnet/iX Access

Telnet/iX provides 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 “Telnet/iX Access” 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 “DTC Switching” 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 “DTC Connection to MPE V Host” 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