Managing the Desktop

A "black box" means you don't have to concern yourself with a device's inner workings. Don't worry yourself with details, just let the product engineers take care of what's going on inside. The problem: Network managers have many black boxes attached to their networks, but users expect them to know what's inside. Except you can't tell your user , who's complaining that he can't print and the network doesn't work, that the manufacturers of these black boxesworkstations, printers, and softwareassumed that the network managers didn't need to be concerned with the magic inside.

Network management has largely been focused on managing network devices, not the devices attached to the network. Administrators savvy to the Simple Network Management Protocol (SNMP) can tinker with the internals of routers, bridges, and hubs, deftly setting device parameters and diagnosing problems. But networks have far more workstations, adapter cards, and printers than internetworking devices. And those are mystical entities, mostly without SNMP agents .

The Desktop Management Interface (DMI) could help bring those dark corners of the network into broad daylight . Products, including servers, desktop computers, and adapter cards, implementing DMI for management will begin to ship this fall. The Desktop Management Task Force (DMTF, Hillsboro, OR) has finalized its DMI specification, and in July 1994 it provided a DMI software development kit for DOS, Windows, and OS/2. Product makers can use this kit to write DMI agents for their products, which ideally will make them easier to manage.

Five product types can benefit from DMI: PC platforms, such as desktops and servers; hardware and software components , such as operating systems, application software, video cards, fax modems, and network adapters; network and local management applications; peripherals, such as printers and mass storage devices; and management consoles.

For every DMI-managed device, the network manager will be able to determine what the device is, who made it, where it's installed, and other relevant information. With those capabilities alone, taking inventory of network devices might be less of a nightmare than it currently is. Network managers will be able to glean this information from their desks, using management software, rather than having to physically go to the site and unscrew the device cover to look inside. Beyond that, manufacturers can use DMI to configure and diagnose their products. Now that's a real boon to productivity.

How DMI Works

Implementing DMI-based management involves the management application, the local agent, which runs on the desktop computer, and the hardware and software components being managed. These parts utilize the three elements of DMI: the Management Interface (MI), the Service Layer, and the Component Interface (CI). Figure 1 shows the DMI architecture and its relation to devices.

Figure 1: A management application can access and configure the managed components via the DMI Management Interface (MI). It can also respond to events occurring in its managed components. The local agent provides the services for managing the individual components. The Management Information Format (MIF) file describes the component's manageable aspects.

The management application can retrieve a list of managed components, access the specific components, and configure the components via the DMI Management Interface. The management application can also respond to events that occur in its managed components.

Each DMI-managed desktop has a local agent, which provides the services for managing the individual components. The local agent presents a common interface to management applications. It is also responsible for coordinating requests from management agents with actions to be executed by the components. The local agent is the embodiment of the DMI Service Layer. The Service Layer must be tuned to a specific operating system, and the first implementations are for DOS, Windows, and OS/2. Implementations for Unix and Windows NT are on the drawing board.

Because the Service Layer runs directly on the desktop computer, its memory footprint is crucial. Efficiently running on existing systems, including low-end PCs, is essential for the success of DMI. One reason SNMP is not widely used on desktop computers and their internal components is because of heavy memory and processing requirements. For the DOS Service Layer, the DMTF targets the TSR to be 14KB and loadable into high memory. In Windows, the Service Layer will be a Dynamic-Linked Library (DLL). For memory-constrained systems, the local agent can also operate as a network proxy, just as in SNMP.

The local agent communicates with the managed components via the DMI Component Interface. The Component Interface gets and sets the component devices' attributes. Component categories include PCs and servers, network adapters, printers, operating system software, application software, and modems.

But the DMI isn't only about the network manager initiating actions. DMI-managed components may initiate events when some undesirable action has occurred, such as discovering a virus or exceeding a preset limit for disk space. The component notifies the Service Layer, which in turn communicates the event to the management application. From there, the network manager can be notified or an action may be taken automatically, depending on the management application itself.

The DMI relies on a Management Information Format (MIF) file to describe the manageable aspects of a particular component. The MIF, which is an ASCII file, guarantees a basic level of information, called the standard component ID group, that even existing equipment can provide. In the standard component ID group , the product name , version, serial number, and the time and date of last installation are mandatory. The ID number is assigned on the basis of a device's order of installation relative to the other system components.

Each group also contains a component name, ID, and class. A management application can use the class identifier to find groups of a certain type, such as LAN adapters.

Each component typically has one or more groups in the MIF, and each group contains one or more attributes that describe the component. The product manufacturer chooses to include either DMTF-specified groups or private groups. For example, a fax modem manufacturer might write MIFs for the standard fax group, the standard modem group, and a private MIF for its own product.

Devices Get Miffed

With the release of the DMTF developer's kit, three classes of products will be manageable: desktop and server systems, adapter cards, and printers. Future classes include software, mass storage, and servers. Let's get an understanding of what parameters the DMI lets you see and control.

The systems group accesses information relative to a PC motherboard. With a DMI-instrumented PC, the network manager will be able to find out the system name, location, primary user name, user phone number, system uptime, system date and time, bus architecture, and slot count. The system's MIF also defines another group of attributes that relate to plug-in cards, such as video cards. For those, the network manager will be able to find out the model, part number, revision level, warranty start date, warranty revision, warranty duration, and support phone number.

For the adapter card MIF, the network manager can discern the driver type (Open Data-Link Interface, Network Driver Interface Specification, NetWare 3.x, NetWare 4.x, LANtastic, and so on), topology type (Ethernet, Token Ring, LocalTalk, T1, and so on), connector type (RJ-45, BNC, DB-9, for example), bus width, version and size, board number, permanent and current network addresses, data rate, buffer memory size , total number of bytes and packets both transmitted and received, and the total number of errors transmitted and received.

For printers, the network manager will be able to determine whether the printer is a part of the IEEE 1284 or Network Printer Alliance (NPA) group. For NPA printers, administrators can discover how much memory the printer has, whether it's duplex, and its speed, for example.

What About SNMP?

If you're thinking the DMI sounds remarkably like SNMP, then you're on track. The difference is that DMI was designed to run on desktop systems, which typically don't have the extra horsepower to run resource- intensive SNMP code. The DMI MIF is sufficiently akin to the SNMP MIB that if the management-application vendor so desires, MIFs can be mapped to MIBs. Standard SNMP network management platforms, such as Sun's SunNet Manager, will be able to communicate with DMI applications. The DMI can also be mapped to use the IEEE 802.1B LAN Management protocol, which is Common Management Information Protocol (CMIP) over Logical Link Control (LLC) or CMOL.

Behind The DMI Curtain

The DMTF was started by Intel in 1992, and critics viewed it as an Intel-centric specification. The DMTF now operates independently of Intel and is a nonprofit organization. It has three levels of membership, depending on the level of involvement your company prefers, from defining the specifications to implementing them.

Few people would be surprised to find out that Intel plans to incorporate DMI into all of its networking products, and in fact, its 10/100Mbps Ethernet cards, the EtherExpress Pro/100 includes DMI agents. Intel also talks of incorporating DMI directly into its CPUs.

DMI also has some big-league support. For example, Microsoft will implement DMI in Windows 95at least in some form, according to Chris Thomas, the DMTF evangelist. The LAN Adapter Working Group includes 3Com, IBM, Intel, Hewlett-Packard, IBM/Pennant, Lexmark, QMS, Tektronix, and Xerox. The PC Platform Working Group includes AST, Compaq, Dell, and HP.

What Does It All Mean?

To say networks are heterogeneous is nearly a clich, but as many different vendors ' hardware and software products sit inside desktop computers as make up the physical network. Peering into desktop devices is largely a manual labor. But DMI provides a vendor-independent, software-based means of managing desktop pods of heterogeneity.

DMI applications will debut this fall, first for PCs, LAN adapter cards, and printers, but eventually DMI will worm its way into operating systems, applications software, and SNMP management platforms, giving network managers a way to see and control most things that reside on the network.

This tutorial, number 71, by Patricia Schnaidt, was originally published in the July 1994 issue of LAN Magazine/Network Magazine.