The CPA Journal Online
`August 1989
`
`Local area networks - enhancing microcomputer
`productivity.
`
`by Leitch, Al
`
`Abstract- Local area networks (LANs) are computer communication networks linking
`microcomputers within a distinct geographical area. LANs offer microcomputer users the utility
`and capabilities of mainframe multi-user systems. LANs also offer flexibility because individual
`workstations can be used independently as stand-alone systems. LANs enable microcomputers
`to share hardware, allowing for a higher utilization rate of peripheral devices and substantial cost
`savings. LANs also allow the sharing of data and software. Multiple users can access a central
`database simultaneously, eliminating the need for multiple copies and reducing inefficiency.
`Additionally, LANs enable microcomputers to share data processing tasks, providing the data
`processing capabilities of a mainframe systems.
`
`To overcome these deficiencies, an increasing number of users are installing local area networks
`(LANs). A LAN is a communication network that links microcomputers within a limited geographical area.
`A microcomputer attached to the LAN, commonly referred to as a workstation, is able to share hardware,
`software, and data with other microcomputers. This capability creates a data processing environment for
`the microcomputer similar to that of larger mini- and mainframe computer systems.
`
`LAN Technology
`
`Hardware and Software. The hardware elements that comprise a LAN are illustrated in Figure 1. A LAN
`consists of two or more microcomputers, electrical cables, at least one network server, and an interface
`board for each microcomputer. Zero-slot LANs do not use an interface card; however, their data-carrying
`capacity is generally reduced substantially. The interface board is installed in one of a microcomputer's
`expansion slots as illustrated in Figure 1. Electrical cable is connected to the interface card creating a
`communication pathway from the microcomputer to every other microcomputer and server attached to
`the network.
`
`LAN servers are microcomputers that provide or share a data processing resource with other
`workstations. For example, a disk server provides disk storage and/or access to stored data. Network
`servers are usually powerful microcomputers used in either a dedicated or nondedicated mode. As its
`name implies, a dedicated server is used exclusively to manage a network resource. Conversely, a
`nondedicated server may be used as a workstation while concurrently providing a server function.
`However, under heavy network demands, its performance as a workstation and as a server may
`deterioate substantially. Other resources commonly managed by network servers include letter quality
`printers, digitizers, plotters, and modems
`
`A LAN, like any computer, is managed by its operating system. A LAN's operating system manages the
`hardware on the LAN, controls access to the network and its resources, as well as implements and
`coordinates users' requests. The performance of a LAN is determined, in part, by the characteristics of
`its operating system. currently, several operating systems are widely used. This offers a greater
`opportunity for finding a LAN suitable for the user's unique operating and data processing requirements
`since no single operating system is optimal for all business environments. The hardware and software
`elements previously described are integrated through network topology, transmission media, and
`protocol to form a LAN. These technological issues are an integral part of a network and determine, in
`part, its performance and operating characteristics. While a technical knowledge of these issues is not
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`Smart Mobile Technologies LLC, Exhibit 2020
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`IPR2022-00807, Apple Inc. et al. v. Smart Mobile Technologies LLC
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`needs to use a LAN, an awareness of their role permits a more knowledgeable application of LAN
`technology. It also aids in understanding network problems and determining an appropriate solution.
`Topology. Network topology refers to the configuration used to physically link workstations and servers.
`The three most commonly used topologies are the ring, star, and bus. As illustrated in Figures 2 and 3, a
`ring uses a closed loop while a star uses a central hub as the communication pathway between network
`nodes. A bus, Figure 1, uses a central cable connected by shorter drop cables to link each workstation
`and server to the network.
`The communication configuration of each topology has certain advantages and disadvantages. A ring is
`the simplest topology for a network protocol to manage. However, it tends to be the most unreliable,
`since the failure of a workstation or cable break disrupts network communication, thereby disabling the
`LAN. A star topology reduces this risk by employing a dedicated pathway from each workstation to the
`central hub. The failure of the workstation at the central hub, however, will disable the network. A bus
`topology requires less cable than a comparable ring or star and is the most flexible topology for adding
`or deleting workstations and servers from the network. However, a break in its cable may disable the
`network.
`Transmission Media. Twisted pair and coaxial (commonly called "coax") cables are the most popular
`electrical mediums used to connect workstations and servers. Twisted pair and coaxial cables are
`illustrated in Figure 4. Both radiate their signal outside the cable, making it easy for a potential
`eavesdropper to intercept. Conversely, the radiation emitted by other electrical sources such as phone
`lines or fluorescent lights is received and transmitted as background noise. This interference may distort
`cable's signal and introduce errors into its transmission.
`Maturing technologies for implementing a LAN include fiber optics and infrared. Fiber optic cable is
`significantly superior to both twisted pair and coax in data-carrying capacity, immunity from electrical
`interference, and transmission distance. Since it does not radiate a signal outside its cable, fiber optics is
`the most secure type of electrical medium currently available. The major disadvantages of fiber optics is
`its significantly higher cost and skill required to install and implement.
`Network Protocol. Each workstation sends and receives data over a single communication medium, i.e.,
`the network cable. Protocols are the methods used to manage the network's communication traffic. The
`two most commonly used protocols are carrier sense multiple access with collision detection (CSMA/CD)
`and token passing. CSMA/CD requires workstations to monitor network communication and transmit
`only when the network is free. When two or more workstations transmit simultaneously, each workstation
`detects the collision, stops transmitting, waits a predetermined length of time, listens for a clear channel,
`and retransmits. Under light communication loads CSMA/CD provides an efficient method of controlling
`network traffic. However, as network communication increases, its efficiency deteriorates, i.e., more and
`more time is spent recovering from data collisions.
`Token passing sends a stream of data along with a token, a series of bits recognized by each
`workstation. Only the workstation with the token is permitted to transmit. Token passing, effectively,
`avoids, the data collisions inherent in CSMA/CD and other protocols. Consequently, it is more efficient
`under heavy data communication loads. However, if the token is lost or modified, network
`communication may be disrupted.
`Network Administrator. A LAN, like any computer system, must be managed to achieve optimal results.
`Responsibility for managing the network is usually delegated to an individual with computer,
`administrative and, perhaps most importantly, people skills. The LAN administrator is responsible for
`managing the network. This involves superivising the daily operations of the LAN such as start-up,
`monitoring the hardware and software to see that it is functioning properly, and periodically copying user
`files for backup purposes.
`One of the most important tasks of the network administrator is to serve as a resource person for system
`users. A significant amount of the administrator's time will be spent training users, diagnosing and
`helping them resolve hardware and software problems, and directing them to reference and technical
`manuals. A LAN administrator is also responsible for network security. The administrator, in effect, is
`responsible for all aspects of network usage and performance. A capable administrator is crucial to the
`daily operations of a LAN and ensuring that it fulfills its data processing role.
`
`Network Services
`Hardware Sharing. A most tangible benefit of a LAN is the ability of workstations to share expensive
`peripheral devices such as hard disks, laser printers, and modems. This results in a higher utilization
`rate for peripheral devices, and substantial cost savings. To illustrate this assertion, consider an
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`Smart Mobile Technologies LLC, Exhibit 2020
`Page 2020 - 2
`IPR2022-00807, Apple Inc. et al. v. Smart Mobile Technologies LLC
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`accounting office with seven microcomputers configured with peripherals as indicated in Figure 5.
`Without a LAN, a total of 18 hard disks, printers, and modems are used. With a LAN, a much smaller
`number of larger and more powerful peripherals are used to provide the same services to a larger
`number of users.
`
`Sharing Data and Communication. A major limitation of stand-alone microcomputer systems is their
`inability to share and cooperate in data processing tasks. For example, for several microcomputer users
`to access a database simultaneously, each user must have a copy of the data file. As users modify their
`files, different versions of the data are created. Uncontrolled, this leads to errors in the database as well
`as errors in reports produced from it. Stand-alone systems are similarly limited in their ability to exploit
`the productivity provided by large integrated software packages. For example, an expensive integrated
`accounting package in a public accounting firm may be needed by several accountants to prepare a
`client's financial, payroll, and tax reports. However, only one accountant can access the program and
`data files with a stand-alone system. These limitations have generally confined stand- alone systems to
`personal-productivity tasks. Larger and more integrated data processing tasks are generally delegated to
`multi-user systems such as mini and mainframe systems.
`
`The communication capability of a LAN enables workstations to share data as well as hardware and
`software. Workstations on a LAN are able to access data from a central database stored on the
`network's disk server. Record and file locking are available on most network operating systems to
`prevent users from accessing a record currently being updated. These facilities permit multiple users to
`simultaneously access a database while maintaining data integrity. For example, with a LAN several
`auditors can perform different audit tasks on a common set of client data files. Equally important, the
`firm's tax accountants can access the adjusted financial data to determine the tax liability and deferred
`tax balance needed to complete the audit.
`
`Each auditor and tax accountant can work with the same set of client data files, thereby reducing data
`redundancy and inefficiency associated with using multiple copies of the same data. The ability to share
`data and data processing tasks permits microcomputer users to perform any data processing tasks
`normally delegated to large multi-user systems.
`
`Electronic Mail and Office Automation. Electronic mail is a major, although frequently overlooked, benefit
`of a LAN. Most network vendors provide the ability to compose and send messages to another user or
`group of users of the LAN. A significant benefit of electronic mail is the reduction in "telephone tag"--i.e.,
`leaving a message for someone to call back because they were out when you returned their call. A
`second major benefit of electronic mail is the cost and speed of information dissemination. The cost of
`sending an electronic message and the time required for its transmission are both negligible. If LANs are
`linked to mini- and mainframe computer systems, electronic mail is a potentially powerful means of
`integrating corporation wide communication.
`
`LANs with modems provide unique communication capabilities. Partners and managers from the audit
`site can receive and send messages and files over the phone. Partners and managers can interact with
`audit personnel and review audit data, working papers, and audit problems as if they were at the client's
`office.
`
`Other benefits of a LAN include the integration of microcomputers into mini- and mainframe computer
`networks. A LAN provides the communication facilities for linking an accounting firm's or client's separate
`computer and data processing resources to form an integrated system. A LAN is also a means of linking
`intelligent office equipment such as word processors, copying, and fax machines into an integrated office
`system. A LAN's operating system and communication medium provide the control and communication
`functions necessary to implement office automation.
`
`Stand-Alone System. Up to this point we have examined the benefits of a microcomputer in a multi-user
`environment. However, a most important advantage of LAN is that work stations can operate
`independently of the network. Unlike a terminal on a mini- or mainframe system, a workstation is still a
`computer system under the control of the user. Consequently, it can still be used as a stand-alone
`system. For many users, this capability will be crucial since personal productivity tasks constitute a
`significant portion of their work.
`
`The relationship of a LAN to a mainframe computer and stand-alone system is illustrated in Fiure 6.
`Listed below the symbols representing a mainframe and microcomputer system are some advantages of
`each data processing environment. A LAN extends the operating capabilities of a microcomputer system
`to include many of the attributes of larger multi- user systems. Consequently, a LAN workstation is able
`to exploit the advantages of both data processing environments.
`Summary and Conclusion
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`Smart Mobile Technologies LLC, Exhibit 2020
`Page 2020 - 3
`IPR2022-00807, Apple Inc. et al. v. Smart Mobile Technologies LLC
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`Microcomputer technology has and will continue to have a significant impact upon accountants'
`productivity. Its application to personal- productivity tasks such as financial analysis have resulted in
`significant increases in accountants' efficiency and effectiveness. However, microcomputer usage is
`constrained by the limited abiality of the microcomputer to communicate and share data processing
`resources and tasks with other computer systems.
`To overcome these deficiencies, more users have been installing LANs. Their communication and
`control functions extend the operating capabilities of the microcomputer to that of a larger multi-user
`system. However, unlike a terminal on a mini or mainframe system, a workstation may be used
`independently of the network as a stand-alone system. A LAN thus enables microcomputer users to
`exploit many of the advantages of both a multi-user and a stand-alone system. This capability
`substantially enhances the microcomputer's usefulness at current data processing tasks as well as
`provides opportunities to exploit newer and much more powerful applications.
`Robert Kee, DBA, CMA, is an Associate Professor at the Culverhouse School of Accountancy, the
`University of Alabama.
`
`Al Leitch, PhD, is a Professor at the University of Virginia Polytechnic Institute and State University.
`
`The CPA Journal is broadly recognized as an outstanding, technical-refereed publication aimed at public practitioners, management,
`educators, and other accounting professionals. It is edited by CPAs for CPAs. Our goal is to provide CPAs and other accounting
`professionals with the information and news to enable them to be successful accountants, managers, and executives in today's practice
`environments.
`
`©2009 The New York State Society of CPAs. Legal Notices
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`Smart Mobile Technologies LLC, Exhibit 2020
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`IPR2022-00807, Apple Inc. et al. v. Smart Mobile Technologies LLC
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