¶ … LAN Construction carefully outlines the main hardware and software required in the construction of an efficient LAN for a small company. This paper also illustrates two figures that will assist the reader in understanding the topology and construction techniques of a Local Area Network. This paper also emphasizes on the factors responsible for acquiring the maximum throughput from a LAN. A developer should strongly consider certain features that are highlighted in this paper in order to develop an efficient and manageable LAN. LAN Construction

Within the past decade technologies such as telecommunications, typewriters, copy machines and computers have significantly changed the ways companies conduct business and this evolution of the modern office is continuing with the passing of each day. The need for computers has grown extensively and what has grown with it is the need for them to communicate with each other. Communication is essential as it extends the power of standalone PCs. This is where computer networks such as a Local Area Network or LAN steps in. Some of the advantages of a LAN are communication, management control, cost effectiveness, downsizing and new application software.

The construction of a LAN even for a small company demands careful selection of both hardware and software, which intern depends upon the budget allocated to this project. We are assuming that the company is on one floor. Hence, the LAN to be constructed for the company will too be on that floor. The number of workstations, preferably Pentium III or IV, required for this LAN would be twenty-three. There would be a 24-port switch to connect all the workstations with each other. The wires for the cabling would be Twisted Pair wires. The operating systems installed on each PC will belong to the Windows family.

Before establishing the LAN, the following three points should be pondered upon, namely,

Reasons for having a LAN

LAN selection plan and LAN installation plan

The following factors are essential to consider when selecting a LAN, namely,

Cost

Distance and Medium

LAN Hardware and Software

Number of workstations

Speed

Adherence to established standards

Type of workstations

Applications

Vendor

Number of concurrent users

Expandability

Vendor support

Type of use

Device connectivity

Manageability and Security

The Local Area Network created for a small company will have the following Characteristics, namely,

Transparent use

Mixed hardware and software

High speed

Resource sharing

Media access control protocols

Local ownership

One of the objectives of a LAN is to achieve transparent use, that is, users either web designers, programmers, sales, directors, logistics, administrative officers or administrator connected to a LAN should detect few differences between using a stand-alone microcomputer and using one connected to a LAN. "Most of the devices are transparent in operation and it is only some gateways that require users to alter LAN behavior to incorporate the extra facilities offered" (Andy Sloane, Computer Communications, Principles And Business Applications). Access to the file server's disk should be carried out as though it were a locally attached disk drive. Printing through a network printer ought to be done in the same manner as directing output to a local printer. The only prime difference between stand-alone and LAN PCs should be security. The network user usually must log onto a server by providing a user ID and a password. This requirement too can be made transparent to the user by using a logon script. A logon script or a batch file is a set of network commands that sets up the user's environment. Thus a logon script can be used to set a user's DOS search path, default disk drive and directory, default network printer configuration, start up menu and so on.

The Local Area Network constructed for the company will mostly constitute of microcomputers that is, most nodes on the LAN will be microcomputers. The two servers in the LAN would be the Mail Server and the File Server. A server is a computer that is dedicated to providing one or more services to other nodes. It controls the shared resources and handles all the data requests. In our LAN, the servers will have a larger hard disk and plenty of RAM. In order to maintain good performance, the RAM is used to buffer disks requests. The File Server on our LAN will provide file and disk access services. A LAN may include a variety of microcomputers. With this mixed hardware LAN, it is also common to find a variety of operating systems being used....

An important point to note here is that a combination of mixed hardware and software also complicates the job of LAN administration and configuration. Hence, we will choose an operating system that is both efficient and user friendly.
The LAN for the company is designed to operate in a limited geographical area. The speed of the LAN, like the distance spanned depends on the specific implementation. "The prime difference between a communication path established using a LAN and a connection made through a public data network is that a LAN normally offers much higher data transmission rates because of the relatively short physical separations involved" (Fred Halsall, Data Communications, Computer Networks And Open System).

During the construction of the LAN, our basic goal would be resource sharing. Data, programs and hardware for example, printer and disks are all resources that can be shared. Attaining high LAN transmission speeds requires a high capacity communications medium. Most of the early LANs used the coaxial cable as the transmission medium. Today the popularity of coaxial cable is giving way to the twisted pair wires. The wire that we will be making use of in our LAN is the untwisted pair category 5 wire i.e., UTP-Cat-5E. Among the five categories of the UTP, we chose category 5 because it is certified for speeds of 100 Mbps and as the speed threshold for twisted pair wires increases, category 5 wires will probably be the only one of these five categories supported. A category 5 wire is scheduled for inclusion in 150 Mbps and 1 Gbps LAN specifications. The attenuation and crosstalk characteristics for category 5 wires are better than those of category 4. Shielded twisted pair wires can also be used instead of the unshielded twisted pair wires, but that depends upon the budget allocated to this project. Even though the STP wires are better than the UTP wires, the prime disadvantage of using them is that they are harder to install because of their bulkiness that arises as a result of shielding the wire.

Each network has specific ways in which it gains access to the communication medium, transmits data over the medium and routes messages. LANs generally differ in their methods for doing this. The physical layer of the OSI reference model describes the medium, the connectors required to attach the workstations and servers to the medium and the representation of signals using the medium, for example, voltage levels for baseband transmission or frequencies for broadband transmission. Once connected to the medium, a network node must have the ability to send and receive network messages.

UTP is most commonly connected to network devices via a type of snap-in plug like that used with telephone jacks. Connectors are either male i.e., the plug or female i.e., the receptacle. Male connectors snap into the female connectors and have a repressible tab called a key that locks them in place. Each wire in a cable is attached to one conductor or pin in the connector (Behrouz Forouzan, Data Communication And Networking).

The connectors that we will be making use of in our LAN will be Registered Jack-45 or RJ-45 with eight conductors, one for each wire of four twisted pairs.

It is important to note that our LAN would be completely owned and managed by the using organization or company. That is, the organization is responsible for all the equipment and software, including installing and controlling the communication medium. A LAN comes with added responsibilities. Within a LAN many resources can be shared, but one thing that should never be shared is the responsibility for managing the LAN. Since one of the important issues associated to a LAN is security hence, someone who is responsible and has authority must always manage the network.

If cost were not a consideration, then the LAN selection would be much easier. One would buy the fastest and the biggest workstations and server available and use the most comprehensive LAN software available. Since we are constructing a LAN for a small company, cost will be a limiting factor here. We have to manage a good and efficient LAN within the allotted budget. Our LAN will consist of twenty-three workstations, i.e. two web designers, three programmers, five sales, three directors, four logistics, three administrative offices, one administrator, one file server and one mail server. Each workstation needs a LAN Adapter, each of which must have LAN software. "100 Mb PCMCIA LAN adapters will play a vital role in the enterprise network" (A Market Research Report On: Applications, Competitive Technologies, Issues, Markets, Trends And Vendors).

Installing cabling can also be an expensive proposition, particularly in an existing building. An existing building has barriers such as ceilings and walls that restrict your ability to install new cabling. We…