LAN Components

The components of LAN are File server, workstation, network operating system, LAN
cable, Active and Passive hubs etc.

a) Workstation

It is a single-user microcomputer with high power communication facilities. It can
exchange message with other workstations or fileserver.

 Workstations can be of two types: user workstation and server workstation. User
workstation is a microcomputer on the network, which is used to access the network. Service
workstation performs service to process other workstations on the network. User workstation
normally does not process requests from other workstations. Server workstation makes available
all sharable network resources to other workstations. More than one server workstations may be
added to the network such as printer server and fileserver. Normally the server workstation is
the most powerful workstation. Server workstation may be dedicated or non-dedicated. In case
of dedicated workstation, it is not available for other user applications. Non-dedicated server
workstation doubles as an individual workstation and at the same time performs network-related
functions.

b) File Server

File server is actually a process running on a computer that provides the clients access to
files on that computer. The term is loosely applied to mean computer that runs file server
software. In this sense, it is a powerful computer with special software to serve files to other
workstations on the network. The files, which may be program files or data files, are
simultaneously shared by a number of workstations. Novell Netware is a popular network
operating system.

c) Gateway

The gateway assists in communicating between LANs. A workstation may be dedicated
to serve as gateway. This is required particularly when two networks with different technologies
have to communicate with each other. Gateway may also be used to connect LAN with a
mainframe computer.

d) Network Interface Unit

The network interface is a printed circuit board installed in the microcomputer. It may be
called network card, network adapter or network interface unit. It connects the workstations
functionally and physically with the network.

e) Active Hub

Hub is an electronic device to which multiple computers are attached usually using
twisted pair cables. Active hub is a powered distribution point with active devices that drive
distant nodes up to one kilometer away. It can connect up to eight nodes on the network. The
maximum distance carried by an active hub is about 2000 ft.

f) Passive Hub

This hub is a distribution point that does not use power or active devices in a network to
connect up to four nodes within a short distance. The maximum distance covered by a passive
hub is nearly 300 ft.

g) LAN Cable

LAN requires superior cable capable of transferring data at high speed. Coaxial cables or
fibre optic cables may be used for networking computer.

h) Network Operating System (NOS)

The NOS integrates all the network components. The NOS facilitates file and print
serving along with other functions like communications and e-mail between workstations. In
most LANs the NOS exists along with the computer’s operating system.. The computer’s
operating system processes the system requests first and processes them if they can be done with
the workstation resources. If it is not a local request, meaning that the network resources have to
be used, the request is transferred to NOS for carrying out. Thus, the NOS is responsible for
controlling access to data, storage space and sharing of other peripheral resources.

i) Applications Software

Another component of LAN is application software. It has to be ensured that the
application software works in the multi-user environment.

j) Protocols

Data transmission between devices requires protocol. Protocols are sets of rules and
procedures to control the data transmission between computer and other devices. They are
common technical guidelines for communication between devices. They specify the order in
which signals will be transferred, the signal for completion of transfer etc. Only Devices using
the same protocol can communicate directly. Both the sending and receiving devices must use
the same protocol for effecting communication. For communication between devices using
different protocols requires intermediate interpretation device or software.

The protocol performs the following functions:

a) Set up a link with the other device in the communication.
b) Identify the component to other components in the communication (sending device’s
channel ID)
c) Send and interpret the data
d) Provide a continuous feedback on data transmission like data is not being received and
understood.
e) Request for retransmission of garbled data.
f) Engage recovery procedure when error occurs.
g) Provide an acceptable way of terminating transmission so that all devices have completed the
process.
The protocol is embedded in communication software designed to use a particular protocol.
The user need not bother about the protocol as the components involved in the communication
perform the protocol matching. The data communication protocols are of two main types:
asynchronous and synchronous. The synchronous protocol permits continuous data
transmission. The devices in communication must be synchronized with the other. The
transmission is governed by a time interval and not by start-stop bits. For example, clock, in the
modern, sets the time interval.