DCE: All
Dressed Up And Nowhere To Go
By Dan Backman
While TCP/IP offers a lowest common denominator of network communication and interoperability with near-ubiquitous support throughout the network, DCE hopes to raise the bar to the application layer. Laying the foundation for distributed applications across platforms, DCE offers a powerful--and standardized--environment for
distributed applications and centralized management of the network and its applications.
But DCE itself is nothing more than a foundation. Building a DCE cell requires little more than pouring concrete into a hole in the ground, or, in this case, installing and config
uring cell security and directory servers. Installing clients is as easy as breaking shrink-wrap and installing software on the necessary desktops.
To get a better idea of DCE's potential, we rounded up an array of DCE cell servers, including Transarc Corp.'s DCE server for Solaris, IBM Corp.'s Directory and Security Server for OS/2 and IBM Corp.'s DCE for Windows NT (a repackaged Digital Equipment Corp. product). We tested DCE clients on most major computing platforms from various vendors--Gradient Technologies (Windows95, Windows NT and Apple MacOS), IBM (Windows NT and OS/2) and Transarc (Solaris). In addition, we looked at Gradient's Web Crusader, which enables secure Web communication using DCE.
Before we get started, you must first know that without applications that take advantage of DCE's services, a DCE cell does little toward unifying your network. Gradient's Web Crusader was the only application tested.
Goals
If you've begun implementing DCE, there should be an ultimate goal (
or at least an ulterior motive) to the effort. Migrating to DCE means learning to crawl before trying to run--but more important, it means first choosing a destination. Most organizations that rely on DCE do so to support one of three goals: a distributed and unifi
ed file system (DCE DFS), support for specific (usually custom) distributed applications, or centralized network management and single sign-on at the desktop. Implementation usually means rolling out a DCE-based business-critical application and slowly extending the cell to desktops that need to access it.
Of course, installing a complex and costly infrastructure like DCE to support a single application is a magnificent waste of its potential. In a perfect world (or at least in the Open Software Foundation's dreams), DCE would be an integral part of all major desktop and server operating systems. Applications would use DCE's security model and would rely on the cell-directory service; interprocess and network communications would use DCE's remo
te procedure calls (RPCs).
From the user's point of view, a fully integrated DCE network acts as a whole--not a collection of different systems each with its own configuration and each requiring an additional login. A single sign-on system, DCE automatically transmits a user's credentials, authenticating and reducing the number of stateful connections required to simply retain an authenticated session. For the administrator, the Kerberos-based security service provides unrestricted use of secure communications, while the Cell Directory Service (CDS) provides a secure, networkwide registry of configuration and administrative information.
Finally, DCE's distributed services, particularly the CDS and applications like Distributed File System (DFS), encourage data replication whenever possible. This model approaches network fault tolerance similar to the way RAID 5 disk systems use parity striping to overcome minor problems like the loss of a single disk in an array.
Cell Servers
Supporting
a DCE cell requires a minimum of a security server, at least one directory server, a Distributed Time Server (DTS) and application servers to support your core applications. Usually packaged together, security, directory and time servers can be located on a single machin
e (as in our test), or replicated on many slave servers in a large installation.
Since DCE's core services are standardized by and licensed from the OSF, all DCE products should be compatible. This means departments can standardize on disparate platforms and still work together. An engineering division dedicated to Sun Microsystems, IBM or Hewlett-Packard Co. Unix workstations can easily interoperate with the finance department, which uses Windows desktops exclusively, or a graphic design group using Macs.
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