WBEM

- www.dmtf.org

History

Prior to WBEM, standard methods did exist for managing hardware from multiple vendors, most commonly via SNMP, but SNMP had (and has) a number of drawbacks¹. These largely stem back to its origin in handling relatively simple devices such as routers without requiring too much processing welly. There was a definite need for a standard way to manage more complex devices in a consistent manner and an opportunity to learn from the failings of SNMP.

The WBEM initiative began in 1996 as a joint effort between a large group of companies including Cisco, Intel and Microsoft. Their aim was to develop a set of standards to describe hardware and software resources in an enterprise according to a common schema and communicate that information via a standardised mechanism. Control of the WBEM standard was handed over to the Desktop Management Task Force (renamed in 1999 to the Distributed Management Task Force²) in 1998 and they have maintained it since then.

Web-based?

As with the much-hyped web services fad of 2001/2002 the "Web" part of the acronym does not directly refer to web browsers as the user interface. Instead it sets out the aim of WBEM to use the widespread availability of WWW technologies such as HTTP, SSL and XML³ to its advantage, although the management application need not be (and usually isn't ⁴) presented in a web browser. This can be seen as one of the lessons learnt from SNMP which arguably integrated the management data it carried too tightly into the transport mechanism, restricting its ability to change over time. The information available through WBEM can keep pace with advances in technology, to handle new types of hardware for example, without requiring changes to how the data is transported. This is primarily due to the separation of the data model, transport encoding and transport mechanism.

The component parts

• The Common Information Model (CIM) - At the heart of WBEM is the CIM, which makes it possible to describe individual components of a system in such a way that data about hardware or software components from many different vendors can easily be compared and aggregated. The CIM specification also defines the mapping between WBEM and older management technologies such as SNMP. ² CIM takes an object-oriented approach which allows the relationships between items to be expressed and makes WBEM data discoverable (by querying an item about its child items).
• xmlCIM - XML encodings for CIM to convert object descriptions from their existing, usually ASCII text, format to XML. Prior to xmlCIM, CIM information was usually transferred in Managed Object Format (MOF) files and in some cases still is. The windows implementation of WBEM, for example, comes with a MOF compiler - mofcomp.exe.
• CIM Operations over HTTP - The specification for firewall-friendly communication of WBEM information. Security is available via pre-existing technologies used for security on the web: HTTP authentication and SSL.⁵ WMI, the windows implementation of WBEM, does not have built-in support for CIM Operations over HTTP⁶, and uses their Trustworthy DCOM RPC instead.

Current Status

WBEM is currently widely supported by the companies which originated it and is becoming the standard across all vendors. A number of implementations are available depending on your platform:

• Windows - The Windows implementation, known as Windows Management Instrumentation, provides information about pretty much every nook and cranny of the operating system from Windows XP onwards, although WMI was built-in as far back as Windows 98. WMI management is usually done via VB scripts, but it can also be done using perl and javascript if you prefer.
• Linux and Unix folks can use OpenWBEM, originally developed by Caldera spit spit
• Linux also has the IBM implementation of WBEM, SBLIM, which IBM want you to pronounce as "sublime", rather than the more fun "SBLIM!!!1" This implementation now has support for management applications written in Python
• For the Java™ platform, there is the WBEM Services project. ⁷
• Unix, Windows and Linux users can all use OpenPegasus⁸, produced by the Open Group in C++ and supported by HP.
• Solaris users can use Sun's Solaris WBEM Services which is written in (you guessed it) Java.