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Wireless Networking Handbook
(Publisher: Macmillan Computer Publishing)
Author(s): Jim Geier
ISBN: 156205631x
Publication Date: 09/01/96

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Today, the main choices for PC operating systems are Microsoft Windows 3.1, Windows for Workgroups, Windows NT, and Windows 95. The following briefly describes each of these operating systems:

  Microsoft’s Windows 3.1. In 1992, Microsoft introduced Windows 3.1, which provided a more stable environment for running 16-bit Windows and DOS applications than its predecessor, Windows 3.0. Windows 3.1 supports multimedia, TrueType fonts, compound documents (OLE), and drag-and-drop capabilities. Windows 3.1 also runs 32-bit Win32s applications by translating them into 16-bit operating system calls.
  Microsoft’s Windows for Workgroups. Microsoft’s Windows for Workgroups (WFW) is a version of Windows 3.1 that includes built-in peer-to-peer networking and electronic mail. WFW also includes 32-bit file access, which bypasses DOS and replaces SmartDrive with another disk cache for increased performance. WFW includes integrated file sharing, electronic mail (Microsoft Mail) and workgroup scheduling (Schedule+).
  Microsoft’s Windows NT. Microsoft’s Windows NT (New Technology), introduced in 1993, is an advanced 32-bit operating system for Intel 386s and up, MIPS (described later in “Hardware Platforms”), Alpha, and PowerPC CPUs. NT is a self-contained operating system that does not use DOS, and it runs NT-specific applications as well as DOS and Windows applications. Windows NT features include peer-to-peer networking, preemptive multitasking, multithreading, multiprocessing, fault tolerance, and extensive security. Windows NT supports 2 GB of virtual memory for applications and 2 GB for its own use.
  Microsoft’s Windows 95. Windows 95 offers a user interface with folder metaphor, explorer view, and taskbar, providing end users with a more intuitive and easy-to-use Windows platform. The Windows Setup program auto-senses PC peripherals. Windows 95 supports all popular LAN protocols, including TCP/IP, IPX/SPX, and NetBEUI. It also provides Remote LAN connectivity through Microsoft’s Remote Access Server (RAS). Internet access and on-line access are available as add-ons. Windows 95 supports the majority of Windows 3.x applications and existing Intel x86 hardware, as well as 32-bit applications.

Hardware Platforms

A computer hardware platform consists of a central processing unit (CPU), memory, applicable interfaces, and an operating system. If you are deploying an NOS or user workstations, you need to specify a hardware platform for each. Typical hardware platforms include the 386, 486, and Pentium PCs.

As a performance measure, vendors classify their platforms according to the rate at which the machine can process instructions. This unit of measurement is MIPS (Million Instructions Per Second). High-speed personal computers, such as Pentiums, are usually capable of operating at 100 MIPS or greater. A 386 PC usually runs between 3 to 5 MIPS. However, MIPS rates are not uniform because some vendors use the best-case value of the platform and others use average rates. As a result, designers should not consider MIPS as the single factor when sizing up the performance of a hardware platform. Be sure to consider other attributes as well, such as bus and memory speed, memory management techniques, and the operating system.

As you have probably encountered before, there are a large number of options available for personal computers. How do you choose the best platform for your requirements? The best way is to start with the minimum requirements specified by the application and NOS vendors. In most cases, vendors test and certify the operation of their software on various PC configurations. It is a good idea to ask the vendor for recommendations on which platform to purchase.

Communications Software

Once you select applications and a server, you need to specify communications software that interfaces users with the applications. For applications located on the local server, the NOS generally provides this functionality for local users. However, users needing to access resources located at different sites via the Internet or located on a mainframe computer will probably require Transmission Control Protocol (TCP) and/or 3270 emulation software.

Transmission Control Protocol

TCP is a commonly used protocol for establishing and maintaining communications between applications on different computers, and provides full-duplex, acknowledged, and flow-controlled service to upper-layer protocols and applications. For example, a mainframe computer employing TCP software enables a wireless user, having TCP software as well, to log in to the mainframe using Telnet and run the application.

LAN Medium Access

As part of the network design, you need to specify a particular network interface card that provides access to a medium that interconnects the computers.

As described in Chapter 2, “Wireless Local Area Networks (LANs),” there are two common types of medium access: carrier sense access and token passing. Most wireless LAN products today deploy a proprietary form of carrier sense access. Vendors, however, will probably migrate their products to the IEEE 802.11 medium access technique, which is based on a carrier sense access process, once that standard becomes finalized in 1997. Some infrared products use a directed beam to create a token-ring network. With the implementation of a wireless LAN, you need to choose one of these methods.

The choice of medium access depends mainly on information flow requirements. Carrier sense protocols will satisfy most requirements; however, they offer asynchronous, statistical access. In other words, you cannot predict when stations will be able to send data. Therefore, carrier sense networks don’t support the transmission of real-time data, such as voice and video, very well. On the other hand, token passing networks operate in a synchronous manner, offering better support for synchronous, real-time data transfers.

In addition to the wireless LAN technologies and products discussed in Chapter 2, you might need to consider several wire-based standards as part of your implementation process. For example, it may be beneficial to locate a database server on a network with both wired connections to stationary users and wireless access points. As a result, you will need to decide which wired access method is best to use as the backbone network. The three main wire-based LAN standards are:

  IEEE 802.3 (CSMA)
  IEEE 802.5 (token ring)
  ANSI Fiber Distributed Data Interface (FDDI)


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