will have at least enough storage allocated to handle the
data being written or read at the port.
A port name can be used instead of an address to
refer to a port. A name is normally easier to remember
than an address. Operating systems sometimes have
predefine names associated with certain ports. For
example, DOS reserves COM1 and LPT1 to refer to the
first serial and parallel ports, respectively.
Analyzing the configuration of the network can be
accomplished in two different ways. The first and
simplest way happens when the computer is turned on;
the operating system goes out and checks the
configuration. The second way is accomplished by
using an application to test whether a remote device is
properly connected to the system. The use of an
application is the best way to analyze the configuration.
The application tests the remote device by sending
out a signal to each device and waiting for the signal to
return. This process is called pinging. The ping sent
out is called an echo message, and the reply is called an
echo reply message. The application sends out the echo
message and, if the device is properly connected, it
sends back an echo reply message. The receipt of this
echo reply indicates that there is a viable connection.
Some version of application software reports on how
long it took to receive the echo reply and any lost
replies. These reports provide information about the
traffic and noise levels on the network.
SYSTEM RESOURCE LIMITS
The advantage of a network is it allows several
people to share resources, both hardware and software.
Hardware resources refer to printers, disk drives, CD-
rom drives, scanners, and modems. Software resources
include operating system, drivers, applications (word
processing, database, etc.), management software, and
data files. To avoid problems, such as slow response
time and unavailability of resources, you must know the
limits of the system resources.
The limitation involved with hardware is going to
be waiting. A particular piece of peripheral equipment
can be accessed by one user at a time. Only one job can
be printed at a time, and only one user can be using a
single modem at a time. This small inconvenience of
access outweighs the cost of several different pieces of
the same type (i.e., several printers or modems).
No matter which software package, whether
application, mail, or operating system, there is a limited
number of users that can use the software at one time. It
is far cheaper to buy one multi-user package that allows
for 25 users than to purchase 25 individual copies. But,
it might run just a bit slower than an individual copy.
Networks require the interaction of software and
hardware. The system software to operate and control
the network must be specifically designed for network
operation. The application software/programs to solve
user problems must also be specially designed to run on
a network. Between the system software and the
application software/programs, two pieces of software
are needed. One is the telecommunications access
software. It provides application programs access to
the network so they can send and receive data. The
other is the teleprocessing monitor, which is the
interface between the telecommunications access
software and the application programs. It handles the
details of integrating these two. To install the system
software, as with any software, follow the installation
instructions supplied with the software.
It takes special system software to handle the
unique and dynamic workloads of a network. This
special software is called network system software.
The network system software is sometimes referred to
as the network operating system (NOS). It is different
from the type of system software you normally use on
your stand-alone PC. Network system software must be
able to handle multiple users, multiple peripherals,
network security, and be able to share information and
application software, just to name a few differences.
Normally, network system software runs on the network
server. It includes such things as the networks
operating system software, communications software,
and all the programs needed to manage the sharing of
information and resources on the network. Without it,
there would be no way to coordinate and manage the
many components of a network into a functioning
Network system software provides multitasking
capabilities. If the network is to serve multiple users at
the same time, then the server must be able to perform
tasks so fast they appear to be processed