Datacommunications and Terminal Subsystem (DTS)

DTC

The HP Datacommunications and Terminal Controller (DTC) provides the connection between asynchronous devices and the HP 3000 Series 900 family of computers. Each DTC is housed in its own box and connected to the LAN. There are five types of DTCs currently supported, the DTC 72MX (HP J2070A), the DTC 48 (HP 2345B), the DTC 16 (HP 2340A), the DTC 16iX (HP J2062A) and the DTC 16MX (HP J2063A). Figure 1-2 “HP Distributed Terminal Controllers” represents the location of the DTCs in relation to the host systems, the LAN, and the terminals/printers connected to the network via the DTCs. (Note that the network represented in this figure includes a single MPE/iX system, two DTC 48s, and does not include an OpenView workstation.)

Figure 1-2 HP Distributed Terminal Controllers

If used for direct connections and remote modem connections only, each HP 2345B DTC (DTC 48) can provide connections for up to 48 directly connected devices, 36 remote devices using modems, or a combination of both.

For HP 2345B DTCs, up to three of the DTC's slots can contain a DTC/X.25 Network Access Card. This card provides access to X.25 networks, and can be used to connect asynchronous devices through PAD connections. Alternatively, a single Telnet Access Card per DTC can be used to access MPE/iX systems from ARPA systems.

Each HP 2345B DTC provides six slots, each of which can contain one of the following connector cards:

Each HP J2070A (DTC 72MX) can provide connections for up to 72 local and modem devices, if used for direct and remote modem connections only. It provides four slots, with one slot used for the LAN card, and three slots each of which can contain one of the following cards:

The DTC 16 contains three slots. The first two slots and only the first two slots (card #0 and card #1) can contain direct connect or modem cards. The third slot (card #2) can contain only a DTC/X.25 Network Access Card.

Each DTC 16iX and DTC 16MX can provide RS-232 or RS-423 port connections for up to 16 asynchronous devices. They both have two port connectors built directly into their backplanes, each of which can be connected to a distribution panel which allows either all direct connections or all modem connections. The DTC 16iX does not support ARPA Telnet or X.25 connections. The DTC 16MX provides AFCP connections for the HP 3000 environment and Telnet connections for the ARPA environment; it does not support X.25 connections for wide area networking. The DTC 16MX managed by an MPE/iX host is limited to identical functionality as the DTC 16iX.

	NOTE: Direct and remote connections may be mixed on the same DTC, since its design is modular. A Telnet Access Card and an X.25 Network Access Card cannot be on the same DTC 48. (Note that neither DTC/X.25 Network Access Cards nor a Telnet Access Card may be mounted in slot 0 for DTC 48s.

On networks that are not managed by the OpenView DTC Manager, devices connected through the DTC function as if the connection were made through a single cable between the device and its associated MPE/iX host system. Such DTCs (and the attached devices) can access only their host system, and their operations are controlled by software that is downloaded from the MPE/iX host when the DTC is powered up or reset. The downloaded information includes configuration files that define the devices connected to the system, and operating code to control the functions of the DTC.

If, on the other hand, the OpenView DTC Manager is used for network management, configuration information and controlling code for the DTCs on the LAN are managed and downloaded by the OpenView workstation. Offloading network management functions from the host systems to the OpenView DTC Manager allows for much greater flexibility in how connections can be made through a DTC. For example, it becomes possible for a terminal connected to a single DTC to access more than one MPE/iX or UNIX system (or both MPE/iX and UNIX systems) on the LAN, since configuration files need no longer explicitly define connections to a single host system.

Regardless of which type of network management is used, once the controlling code and configuration information has been downloaded, the DTC is ready for operation. Devices physically connected to its ports and properly configured can then establish communication links with a host computer.

A DTC Self-Test and an offline Self Diagnostic program are available to diagnose any problems encountered when a DTC is powered-on or reset.

When an MPE/iX host manages your DTCs, an online diagnostic program, TermDSM, is available to help diagnose any problems which may occur during DTS operation. Use of the online diagnostics as described in detail in the Troubleshooting Terminal, Printer, and Serial Device Connections manual.

If an OpenView workstation is part of the network, the diagnostic functions otherwise performed through TermDSM are provided instead by the diagnostic facilities that are a part of the OpenView DTC Manager software. See Using the OpenView DTC Manager manual for more information on using these facilities.

Local Area Network

HP 2345B Datacommunications and Terminal Controllers are connected to the system via a Local Area Network (LAN) connection, over coaxial cable which conforms to the IEEE 802.3 standard. Hewlett-Packard provides two versions of this cable, ThinLAN and ThickLAN, each of which provides certain specific advantages to the user.

Each DTC has a unique LAN address, also referred to as the node address or the station address, which serves to identify the DTC as a node on the LAN. You should keep in mind, however, that while DTCs are treated as nodes for purposes of configuration, they are not true nodes in the sense that nodes are normally defined. DTCs are dedicated communication devices; they are not self-contained, general-purpose computer systems.

ThinLAN Connection

Two versions of LAN cable are available. The first version, ThinLAN (Type 10BASE2), is available in connection lengths of up to 185 meters (555 feet), and supports up to 30 nodes. ThinLAN provides an economical solution where DTCs are located fairly close to their associated computer systems. ThinLAN cable is very flexible and easy to install, and can be bent around objects to accommodate its use in confined areas. The ThinLAN is connected to each computer on the LAN via a ThinMau (Medium Attachment Unit), with a small BNC T-connector used to connect each DTC to the LAN. (Note that the ThinMAU for the DTC itself is built into the DTC box.) You can connect up to three segments of the ThinLAN cable with two repeaters, thus extending the length of the LAN to 555 meters. Figure 1-3 “ThinLAN Configuration” depicts a configuration using ThinLAN.

Figure 1-3 ThinLAN Configuration

ThickLAN Connection

The second version of the LAN cable, ThickLAN (Type 10BASE5), offers maximum connection lengths of up to 500 meters (1,600 feet.), and supports up to 100 nodes. Each node on the LAN is connected via a Medium Attachment Unit (MAU). An Attachment Unit Interface (AUI) cable runs between each node and its MAU, as well as between the host computer and its MAU. You can connect up to three segments of the ThickLAN cable with two repeaters, thus extending the length of the LAN to 1,500 meters. A ThickLAN configuration is depicted in Figure 1-4 “ThickLAN Configuration”.

More information on cabling and connection options can be found in the LAN Cable and Accessories Installation Manual.

Figure 1-4 ThickLAN Configuration

OpenView Workstation

As of MPE/iX version A.30.00, an OpenView workstation may also be a part of the Datacommunications and Terminal Subsystem. The OpenView workstation is a personal computer which is properly configured as a part of the LAN, and runs the OpenView DTC Manager software.

The OpenView DTC Manager is an application based on OpenView Windows. It provides an easy to use network management facility that allows you to configure, monitor, and diagnose the network and its components.

The OpenView DTC Manager assumes many of the network management functions that would otherwise have to be performed on an MPE/iX host system, including configuring the devices connected through the DTCs on the LAN and uploading and downloading the code that controls DTC operations.

The functionality of the DTC is expanded when network management is performed by the OpenView DTC Manager. It becomes possible for the DTC to act as a true data communications server, providing access to X.25 networks through the DTC/X.25 Network Access. Network access can include asynchronous connections through a private or public PAD, as detailed in Chapter 7 “Programming for PAD, DTC Telnet, Telnet/iX Server, and VT Devices” of this manual. DTC Telnet enables Telnet users to access MPE/iX hosts.

Additionally, terminals connected through DTCs on LANs managed by the OpenView workstation may be configured so that they are capable of establishing connections with more than a single MPE/iX system on the LAN. This ability is referred to as DTC switching, and is possible because the software that manages terminal connections resides on the OpenView workstation, and not on a specific MPE/iX host system.

When switching is allowed the user at a terminal can select the MPE/iX system to which they want a connection to be established through a special DTC User Interfacer. See DTC Planning Guide for more information on the DTC Services.

Figure 1-5 “Network with OpenView Workstation” depicts a LAN managed by an OpenView workstation.

Figure 1-5 Network with OpenView Workstation