Information system managers are faced with a myriad of PC-Unix integration products all claiming interoperability and to be the best "open system solution". Network computing, the computing paradigm of the 1990s, has demanded network technologies that deliver the computing power and information of the enterprise to the PC desktop. Although legacy technologies such as terminal emulation, and the classic PC-LAN client-server model have served us well, they offer limited connectivity and functionality.
During the 1980s new enabling technologies based on open systems standards such as Ethernet, TCP/IP network transport software, the Network File System (NFS) and the X Window System emerged and gained widespread acceptance, making network computing a reality. Network computing is radically changing the concept of PC desktop connectivity, and the enterprise-wide distribution of information and computing resources.
Forces driving PC-Unix integration
The ability to effectively distribute information throughout the organization is a major force driving the networking of PCs and their integration with Unix systems. Networked PCs empower the work force and increase productivity by bringing information to the desktop. The physical location of applications, information and computing resources becomes irrelevant in network computing environments as applications both remote and local are seamlessly integrated into the PC users desktop. Organizational investment in PC hardware and software mandates the PC's integration within the network computing environment.
Ways organizations benefit from networking PCs and Unix systems include the following:
The evolution of PC-Unix integration
In the beginning, PCs were connected to Unix hosts via serial lines or modems, and/or by running terminal emulation software on the PC, making the PC appear as a Unix terminal. One of the primary motivations for PC-Unix integration was to provide print and file services to the PC user. Terminal emulation software enabled the PC user to run Unix applications in character mode and provided the ability to copy files to and from the Unix host. However, today's PC-Unix integration products provide more than simplistic terminal emulation to proprietary hosts, and have adapted to meet the increasingly sophisticated needs of the PC user in multivendor network computing environments.
Multivendor network computing
The enterprise computing network of the 1990s typically consists of multivendor environments often requiring more sophisticated communication and connectivity technologies. The graphic below illustrates the most common types of communication technologies used in multivendor computing environments.
Open Standards For PC-Unix Integration
Although thousands of PC users still connect to character-based Unix applications with terminal emulation software, and access print and file services with proprietary protocols, the new generation of PC-Unix products are built on open standards integrating TCP/IP, NFS and PC X-Windows software. These open standard solutions are rapidly gaining widespread acceptance as key interoperability technologies for networking PCs to Unix-based computer systems. Emerging in the early 1980s, Ethernet and the TCP/IP protocol suite represented major technological advances in the evolution of PC-Unix connectivity.
Ethernet significantly increased the bandwidth, speed and functionality of networks from snail-like 2400 to 9600 bits/sec of serial lines to warp speeds of 10 to 100 Mb/sec. The TCP/IP protocol suite is a standard for networking Unix systems and has rapidly become a de facto standard for PC-Unix integration. TCP/IP is a feature rich protocol suite that provides interoperability between Unix systems and minicomputer, supercomputer and mainframe computer networks. TCP/IP supports Unix standards such as NFS and the X Window System, a network graphics protocol and windowing system, that enables graphical applications to be distributed across the network. Although a variety of other options (proprietary protocols) exist for connecting PCs to Unix hosts, the TCP/IP protocol suite is scaleable, provides transparent inter-network connectivity (interoperability), and integrates Sun Microsystems' Network File System as a common element.
PC Unix Integration Products
The primary function of PC-Unix integration products is to make host and network resources available to the PC user. Historically, product differentiation has occurred in several areas; the level of product complexity, the Unix host platforms supported, and the PC platforms supported. While the path to PC-Unix integration continues to be one of evolution, new products take incremental steps beyond those that preceded them. New products provide more and more elements of integration, beyond the basic file and print services offered in the DOS LAN environment. Although a variety of solutions exist today for connecting PCs to Unix hosts, the trend is toward products that have synergistic relationships with the PC environment: Windows, Windows NT and OS/2.
The implementation of all PC-Unix integration products is similar in concept. An application resides on the host that communicates with an application that resides on the PC. The PC side application presents the user (sometimes) with an easy to understand interface for complex functions and actions that involve the host, while the host side application serves requests generated by the PC. These requests can include simplistic network services such as print, mail and file services and data backup, or more sophisticated data base queries (SQL) and remote application access via the X Window System.
Network transparency, graphical user environments
PC-Unix integration provides a way for the PC user, in the context of the PC environment, to have access to the world of Unix system functionality and features. PC users want to use network-based information on a dynamic basis, and network transparency is an important goal of any PC-Unix integration product.
PC-Unix integration products should make available to the PC user the resources and capabilities of the host, in a manner that is consistent with the PC user's desktop environment. Many PC users have limited experience with network computing and must be shielded from the complexities of the network and Unix operating systems. If the PC desktop is Windows-, NT- or OS/2-based, the resources of the network must be available and manageable within these environments.
The benefits
The complexity of PC-Unix integration products has increased significantly as user needs have become more sophisticated. In addition to delivering basic network utility services to the desktop that were provided in the traditional PC-client server model the 1980s, today's PC-Unix integration products deliver a highly functional suite of network utility and application services.
Integration of heterogeneous PC environments
PC-Unix integration products facilitate interoperabilty between different PC environments. Employing a host application to service PCs enables heterogeneous PC environments to communicate, essentially using the Unix host as a gateway. By using a Unix host for network utility and application services, different PC environments, such as IBM DOS-, Windows-, Windows NT-, OS/2-based PCs and Macintoshes, can share resources and information. In effect, the Unix host is also functioning as a gateway between different systems.
X Window system interoperability
Traditional access to network based applications via terminal emulation and Unix shells has limited the PC's access to character mode emulation and connection to a single or specific host. However, the new generation of PC-Unix integration software products integrate the X Window System within the PC's environment: DOS, Windows Windows NT and OS/2. PC X-Windows implementations are termed PC X display servers and enable users to access applications from many different computer systems anywhere on the network with a single product. These products use the power of the X Window System to connect to Unix hosts over the TCP/IP protocol suite. Because all variants of the Unix operating system and VMS based systems are based on the X Window System, X provides a common bond facilitating enterprise-wide computer interoperability.
PC X-Window display servers represent one of the most powerful PC-Unix integration technologies available today. PC X display servers are similar to PC terminal emulation software only in the sense that they both establish a connection to networked computers. In contrast to terminal emulators, which emulate a character terminal on a PC, PC X display servers use the X Window System's graphics capability which facilitates the distribution graphics (bitmapped images) across the network.
Some of the benefits of this technology include the following:
PC-Unix integration issues
PC-Unix integration products are inherently complex and may have a significant impact on the local PC environment, the Unix host, and on network resources. LAN-LAN and LAN-Unix integration are also important issues to consider when evaluating a PC-Unix integration solution. Many organizations facilitate interoperability between different LANs, a Novell and TCP/IP network for example, by running dual protocol stacks, IP and IPX on the PC.
Impact on the PC environment
Integrating PCs and Unix systems requires the addition of network transport software, NFS modules and X display servers to the PC, and in some cases an additional network transport (protocol stacks). Network transport software products (TCP/IPand IPX/SPX) that run as terminate stay resident programs (TSRs) in the PCs conventional memory, and can negatively impact PC performance and resources, however they may also provide superior performance.
The addition of network software and PC-Unix integration products can negatively impact the conventional memory of DOS based PCs (640K), especially if two or three network transport software (protocol stacks) are employed. In some cases, as a result of TSRs, RAM CRAM can occur, severely impacting the PC environment. Larger DOS and Windows applications can not be used without disabling communications software. MS-Windows based TCP/IP network transport software products that utilize dynamic link libraries (DLLs) and Virtual Device Drivers (VxDs) within Windows eliminate the need for large TSRs. Although Windows DLL based TCP/IP network transport software still utilize some conventional memory (6-10K), impact on the DOS environment is minimized, and the network software runs primarily in the extended memory. A new generation of Windows based TCP/IP software that employs VxDs is now available, and use no conventional memory.
Peter J. Auditore is director of publications for Hummingbird Communications Ltd., a Mountain View, Calif.-based company that develops PC X connectivity software products and X window system development tools. His e-mail address is petera@shell.portal.com. Hummingbird can be reached by calling 905-470-1203.