Infrastructure servers provide support for wide area network (WAN) communications. This support typically includes support for a subset of IBM System Network Architecture (SNA), asynchronous protocols, X.25, ISDN, TCP/IP, OSI, and LAN-to-LAN NetBIOS communication protocols. In the Novell NetWare implementation, Gateway Communications provides a leading communications product. In the LAN Server and LAN Manager environments, OS/2 communications server products are available from IBM and DCA. In the Banyan VINES environment, the addition of DCA products to VINES provides support for SNA connectivity. UNIX servers provide a range of product add-ons from various vendors to support the entire range of communications requirements. VMS servers support Decent, TCP/IP, and SNA as well as various asynchronous and serial communications protocols. MVS servers provide support for SNA, TCP/IP, and some support for other asynchronous communications. Security at the server restricts access to software and data accessed from the server. Communications access is controlled from the communications server. In most implementations, the use of a user login ID is the primary means of security. Using LAN Server, some organizations have implemented integrated Response Access/Control Facility (RACF) security by creating profiles in the MVS environment and downloading those to the LAN server for domain control. Systems and network management services for the local LAN are managed by a LAN administrator, but WAN services must be provided from some central location. Typically, remote LAN management is done from the central data center site by trained MIS personnel. The discussion in the following sections more specifically describes the functions provided by the server in a NOS environment. Requests are issued by a client to the NOS services software resident on the client machine. These services format the request into an appropriate RPC and issue the request to the application layer of the client protocol stack. This request is received by the application layer of the protocol stack on the server. File services handle access to the virtual directories and files located on the client workstation and to the server's permanent storage. These services are provided through the redirection software implemented as part of the client workstation operating environment.

To diminish the effort and effect of installation and maintenance of software, software should be loaded from the server for execution on the client. New versions can be updated on the server and made immediately available to all users. In addition, installation in a central location reduces the effort required for each workstation user to knob the installation process. Because each client workstation user uses the same installation of the software, optional parameters are consistent, and remote help desk operators are aware of them. This simplifies the analysis that must occur to provide support. Sharing information, such as word processing documents, is easier when everyone is at the same release level and uses the same default setup within the software. Central productivity services such as style sheets and macros can be set up for general use. Most personal productivity products do permit local parameters such as colors, default printers, and so forth to be set locally as well. Backups of the server can be scheduled and monitored by a trained support person. Backups of client workstations can be scheduled from the server, and data can be stored at the server to facilitate recovery. Tape or optical backup units are typically used for backup; these devices can readily provide support for many users. Placing the server and its backups in a secure location helps prevent theft or accidental destruction of backups. A central location is readily monitored by a support person who ensures that the backup functions are completed. With more organizations looking at multimedia and image technology, large optical storage devices are most appropriately implemented as shared servers. High-quality printers, workstation-generated faxes, and plotters are natural candidates for support from a shared server. The server can accept input from many clients, queue it according to the priority of the request and handle it when the device is available. Many organizations realize substantial savings by enabling users to generate fax output from their workstations and queue it at a fax server for transmission when the communication costs are lower. Incoming faxes can be queued at the server and transmitted to the appropriate client either on receipt or on request. In concert with workflow management techniques, images can be captured and distributed to the appropriate client workstation from the image server. In the client/server model, work queues are maintained at the server by a supervisor in concert with default algorithms that determine how to distribute the queued work. Incoming paper mail can be converted to image form in the mail room and sent to the appropriate client through the LAN rather than through interoffice mail. Centralized capture and distribution enable images to be centrally indexed. This index can be maintained by the database services for all authorized users to query. In this way, images are captured once and are available for distribution immediately to all authorized users. Well-defined standards for electronic document management will allow this technology to become fully integrated into the desktop work environment. There are dramatic opportunities for cost savings and improvements in efficiency if this technology is properly implemented and used. Article 10 discusses in more detail the issues of electronic document management.