web laboratory for computer network

Web Laboratory forComputer NetworkNENAD JOVANOVIC,1 RANKO POPOVIC,2 SUZANA MARKOVIC,1 ZORAN JOVANOVIC1

1Department of Computing and Informatics, Advanced Business School, Blace, Serbia

2Department of Computing and Informatics, Singidunum University, Belgrade, Serbia

Received 7 July 2009; accepted 18 January 2010

ABSTRACT: Current technologies give us the ability to enhance and replace developmental classes with

computer-based resources, often called Web laboratories. Web laboratories have become a very useful support for

practical aspects of teachingmethods. This article presents a Web-based laboratory, whichmakes learning of base

principles of computer network possible. �2010 Wiley Periodicals, Inc. Comput Appl Eng Educ; Published online in

Wiley InterScience (www.interscience.wiley.com); DOI 10.1002/cae.20417

Keywords: IP; computer network; e-learning

INTRODUCTION

Traditional educational system, which is mostly based on

theoretical learning, does not give good results when it comes

to the qualification of students for solving practical problems.

Theoretical learning must be combined with practical experience,

while laboratories represent ideal places for upgrading theoretical

knowledge with practical skills.

Acceleration in development of technologies, and possibil-

ities of informatical age, intend to change playing rules in

education. Educational system should be adapted and give us new

educational forms which will maintain new students to use

technological achievements in educational processes, without

addition of money expenses, and their physical absence will not

be a disadvantage.

As an answer to this challenge, many educational institu-

tions give response in the development of online educational

programs. When we have a possibility for transfer of educational

content over the Internet, it is necessary to give a student an

online interaction with real or virtual equipment such as

computers, routers, electronic circuits, lasers, microscopes, etc.

When we have online control of equipment, we create an online

laboratory.

In order for online labs to be an adequate tool in the process

of education, they must realize three academic principles [1]:

* Authenticity: Enable easy division of development tools.

* Complex: Possibility of visualizing a complex process.* Collaboration: Possibility of computer communication.

Online laboratories are used in technical [2�6]

and mathematical [7�9] sciences, and in the field of social

sciences.

On the Internet we have different types of online labs. Some

of them have an online interface for access on the physical

devices, where we may adjust, control or read from a remote

place [2]. They enable creation and online publication of

exercises which are based on those devices.

A second type of online laboratories works with simulations

of real equipment with the purpose of representing functionality

of these devices [3,5,6]. These environments allow students to

configure devices in the same way like with the real equipment,

but experiments are derived in a controlled and robust environ-

ment.

Today, we have an online education system which may

simulate real equipment [4]. In distinction of simulation,

emulated devices execute process of information in real time

and can be used in educational purposes, and in process of

researching.

Some online laboratories are realized in the form of Java

applet and enable simple interactive work and visualization of

processes in observed system [7,8].

In this article, educational system is available [10] which has

several tools that are grouped in the group system named ‘‘Web

laboratory for computer network.’’ While preceding systems

belong to some specialized area, our system covers several areas

and has the possibility of use as component for distant learning in

the process of engineer education for informatics. The system isCorrespondence to N. Jovanovic ([email protected]).

� 2010 Wiley Periodicals Inc.

1

interactive and covers system simulation and process visualiza-

tion and has the possibility of explaining complicated work of

computer networks.

WEB LABORATORY STRUCTURE

Web laboratory for computer network [10] consists of two parts:

* WNetSim: Computer network simulator [11].* Basic concept of IP networking.

WNetSim: Computer Network Simulator

WNetSim presents an environment which allows us to visualize

and simulate a process in computer network with any topology.

The purpose of the simulator is to help students comprehend basic

principles of acting of one TCP/IP computers network as a part of

the educational system of computer network. Information

technologies progress work on instruction and learning methods

from different domains such as computer networks. Processes

that occur in computer network during data exchange between

network devices are complex and they are executed in very

short time slices, since the consumer is not in the state to follow

and understand what happens in computer network. The main

purpose of our simulator is to present these processes visually. In

addition, its features like topology editor, and simulation of real-

time network scenarios makes it a suitable tool for undergraduate

teaching as well as for research.

WNetSim simulator is Web based and enables animation

and visualization of process data transport in computer network.

The main reason for this simulator development is its educational

usage. WNetSim simulator allows students to design computer

network of arbitrary topology with arbitrary chosen components,

to configure network components by using command line

interface, and to see data frame flow on different locations in

network, as well as, content of encapsulated data. Simulator

facilitates fundamental perception of protocol operating, such as:

Ethernet, IP, ARP, PPP, etc. It is possible to introspect switching,

routing, and other processes in network.

Network simulator also includes a comprehensive lab menu

that contains structured labs for users to run.

Network simulator allows students to design, build, and

configure their own network with drag and drop design. The

WNetSim monitor can be used to observe the real-time path of a

packet as it travels through the devices in a created network.

Students can view the progress of a packet.

Basic Concept of IP Networking

Internet address, or IP address, is a 32-bit numeric address which

is to be written as four 8-bit numbers separated by point, whereby

the 8-bit numbers are to be presented as decimals. For example,

192.101.121.6.

There are following kinds of IP addresses:

Static address:

* Subscribed manually by network administrator.* They are used in small range networks.* They require careful assignment and verification to avoid

repetition.

Dynamic address (bootstrap protocol (BOOTP), dynamic

host configuration protocol (DHCP)):

* Represented by server when the host is to boot.* Subscribed from the corresponding range of address.* At the expiry of ‘‘rented’’ time, address is returned to the

server.

Internet addresses are being qualified as classes A, B, C, D,

and E. IP address consists of two parts: the network part (NetID)

and the HostID. The NetID part uniquely identifies the network

and the HostID indicates the address of the node on the network.

Different types of IP classes are defined in order to fulfill the

needs of different extents of networks.

Class A IP addresses have 7 bits reserved for NetID and 24

bits for HostID. They are designed for very large networks

and can identify 16,777,214 (224� 2) computers in 126

(27� 2) networks. The first octet in class A addresses could

be a number from 1 to 126.

Class B addresses are mid-ranged. They are suitable for

mid-range and large organizations. Network identification

could be done with 14 bits, and network nodes are identified

with 16 nodes. These addresses can identify 65,534 (216� 2)

computers in network. The first octet in an IP address should

be in the range of 128�191.

Class C address is using 21 bits for NetID, and 8 bits for

HostID. These addresses are designed for small networks

and they can identify 254 (28� 2) computers in network.

The first octet in class C IP address should be in the range of

192�223.

Class D addresses are designed for multicast; they are not to

be used for addressing individual computers. The first octet

in the address should be in range of 224�239.

Class E addresses are used in experimental cases. The first

octet in the address should be in range of 240�255.

Several addresses are reserved for special purposes.

* HostID can never be 0. If all bits in HostID are equal to zero,

then the said IP address is used for indicating the network

(network address).* HostID can never be 1. If all bits of HostID are equal to one,

then the package should be delivered in a diffusing manner

to all computers in network and the above-mentioned

address is to be called broadcast address.

The first address in every network (grade) represents the

network address, and the last address is reserved for the broadcast

address.

IP network could be divided into smaller networks, called

subnetworks (subnets). The division of network into subnetworks

enables larger flexibility and more efficient use of IP addresses.

For example, the network with the network address 177.28.0.0

could be divided into subnetworks with addresses: 177.28.1.0,

177.28.2.0, 177.28.3.0, 177.28.4.0, etc.

The subnet address is created by using bits from HostID

fields as subnet fields. The number of borrowed bits is variable

and is determined by subnet’s mask.

The subnet’s mask uses the same format and the same

manner of representation as IP address. The subnet mask contains

2 JOVANOVIC ET AL.

number 1 in the position of all bits belonging to NetID and

SubNet fields, and contains 0 in all bits belonging to HostID

fields.

The procedure of realization of subnetworks requires

previous analysis of the following questions:

* How many addresses are needed for network segments? (A

network segment is an entity separated from other entity by

a router.)* How many network segments will be needed in the future?* What is the maximum number of hosts on the largest

segment?* What will be future hosts’ needs in any of the segments?

IP Calculator. IP address calculator, which is a part of the

system for learning the basic concepts of IP networking, can serve

for calculating all previously mentioned elements of an IP

address. The basic screen of an IP calculator is shown in Figure 1.

IP calculator enables the entry of an arbitrary IP address in the

field IP address and the calculation of all needed data related to

the given address: class, network address, broadcast address. Data

are shown in decimal and binary forms.

In case if we want to divide a given network on a certain

number of subnetworks, we need to define how many bits have to

be borrowed from the HostID part of an IP address. We can do this

in two ways. We can define the number of bits which define the

network and the subnetwork through a slider or we can enter the

IP address in the form of a Classless Inter-Domain Routing

(CIDR) notation (e.g., 198.123.56.23/28).

For example, an IP network address 198.123.56.0 which

belongs to class C is given. If we want to divide the given IP

address into at least 10 subnetworks, then we need to separate

from the HostID part of an IP address 4 bits, because 24> 10. In

that case, bit of a subnetwork address is 28 (Fig. 1a).

We can see that the subnetwork mask is 255.255.255.240

and that in this way we can form a maximum of 14 subnetworks

with a maximum of 14 hosts in each subnetwork.

By pressing the button, near the maxSubNet field, we can

get a list of all available subnetwork addresses, with a range of

valid IP address hosts, as well as the broadcast address for each

subnetwork (Fig. 1b).

Work With the System. After entering the name and the surname

of a student and pressing the button START, the first window of

application for the work with IP addresses opens. This application

consists of seven parts:

(1) Numerous systems.

(2) The classes of IP address.

(3) IP network subnetting.

(4) Calculating the subnet and broadcast.

(5) CIDR.

(6) Network topology 1.

(7) Network topology 2.

The first part is the Web application for work with numerous

systems, which is made of an interactive system in which

questions to which students give answers are generated.

Questions are related to the conversion of randomly generated

values from one into another number system. Number systems

with the base of 2, 8, 10, and 16 are dominant. After answering

the questions, the student can see the statistics for correct/

incorrect answers (Fig. 2).

By clicking the button next, we go onto the next part.

In the second part, it is necessary to answer questions

regarding the given IP address, which is generated randomly

(Fig. 3). It is necessary to write down the binary code of the

address, the class of address, to define address’ scope, the extent

of the first octet of given IP address’ scope, considered subnet’s

mask and network address. Then we need to determine the class

of four IP addresses, generated randomly, and enter the answers in

the adequate text fields.

In this example, there is a randomly generated C class

address 195.45.123.19. The value of first octet for C class

is between 192 and 223. This IP address has a place in

network with the following address: 195.45.123.0. The

defaults network mask is 255.255.255.0. The binary address

is 11000011001011010111101100010011. Generated IP

addresses, in this example, 170.119.35.197, 179.111.75.78,

Figure 1 IP calculator. (a) The basic screen of IP calculator and (b) a list of all needed data.

WEB LABORATORY FOR COMPUTER NETWORK 3

25.195.42.97, and 73.118.33.102 belong to classes B, B, A, and

A, respectively.

In the third part of the exercise (Fig. 4) it is necessary to

define how many data bits should be borrowed from the host part,

so that the given network address (201.45.123.17), which is

generated randomly, could be divided into a distinctive number of

subnets. Then, it is necessary to define the subnet’s mask and to

show the subnet’s mask in binary form.

In this example, the task is to divide the network into

10 subnetworks. Since 24¼ 16, the conclusion is that 4 bits

should be borrowed from the host part. The mask for 4 bits is

240, or to be more precise the subnet’s mask will be

255.255.255.240.

It is necessary to fill the table with several valid subnet

addresses. Also, one should define the scope of useful addresses

for every subnet and broadcast addresses. The possible numbers

Figure 3 Web application—the second part.

Figure 2 Web application—the first part.

4 JOVANOVIC ET AL.

of subnets in this examples (according to defined formula:

2n� 2): 24� 2¼ 14. The numbers of hosts in each subnet are

24� 2¼ 14. For example, first subnet could be 201.45.123.16.

Broadcast address for this subnet is 201.45.123.31. The range of

useful hosts addresses is 201.45.123.17�201.45.123.30.

In the fourth part (Fig. 5), it is necessary to fill the table. In

every row of the chart IP address and subnet mask are randomly

generated, and the user should calculate the subnet and broadcast

to fill it in the appropriate field.

In the specific example shown in Figure 5, the first generated

IP address is 7.213.175.179 (class A) and the subnet mask is

255.255.255.128. Which subnet is this address part of?

According to the subnet mask we can conclude the

following: there are 131,070 (217� 2) subnets, and the increment

for each is 128 (27). The address of first subnet is 7.0.0.128,

the second one 7.0.1.0, etc. and the address of the last subnet

will be 7.255.255.0. IP address 7.213.175.179 is between subnet

7.213.175.128 and subnet 7.213.176.0. Therefore, we can

Figure 4 Web application—the third part.

Figure 5 Web application—the fourth part.


conclude that our randomly generated IP address belongs to

subnet 7.213.175.128. This value is to be written in appropriate

fields in Figure 8. Broadcast address for this subnet is

7.213.175.255.

In the fifth part (Fig. 6), IP address in CIDR notation is

given, generated randomly. The user should determine an

equivalent subnetwork mask, the number of addresses in a given

CIDR block, subnetwork address, the first and the last addresses

in the given CIDR block, and the broadcast address.

In the sixth part (Fig. 7a), a network topology is given, and a

student must assign a proper subnet mask, for a random generated

network IP address, and bring in text fields with valid subnet

addresses.

In the seventh part (Fig. 7b), a network topology and a

randomly generated network IP address are given. A student must

determine an adequate subnetwork mask and to fill in the adequate

text fields the IP addresses of the interface router and the computer

IP address, taking care of where special subnetworks belong.

At the end or after each part of the application, the user can

see his achieved results by clicking the results button (Fig. 8).

ASSESSMENT

Assessment of knowledge is usually done in a traditional way, by

oral examination or by written tests. However, nowadays a large

number of tests for studying and assessing which is done by a

computer are developed. The suggested system generates

computer tests which represent a very efficient way of knowledge

assessment. The assessment time is decreased as well as the

distribution of results. Basically, at the time when the examinee

finishes a test, the system generates a report (a grade or a

percentage and a recommendation for studying those fields, the

questions from which were badly done, etc.).

Learning styles represent different approaches or ways of

studying. Every student, when acquiring knowledge, gives

advantage to the information which he/she receives through a

certain hearing modality and therefore, by using that informa-

tion, learns in the most efficient way. According to that

modality, the basic topology of learning styles is as follows

[12]: visual, auditory, and tactile/kinesthetic learning styles.

The visual learning is dominant in those who acquire

information when it is presented visually in the form of text

(graphical-visual) or a picture. They mostly prefer individual

learning. Those who find it easier to learn by listening to

lectures, discussions, exchange of ideas use the auditory

learning style. This is the reason why it is characteristic of

this learning style for students to work in pairs or groups. Those

who take notes, draw pictures and diagrams during the learning

process, in order to memorize the information more easily use

the tactile/kinesthetic learning style. They learn best through

movement, games, acting, or concrete action, actively explor-

ing the physical world around them.

According to the previously mentioned learning styles, we

have tested a group of students (25 students) and arrived at the

following results.

First, preliminary testing was done which was carried

out in order to determine the learning styles of students and

the way to express knowledge (http://www.businessballs.com/

vaklearningstylestest.htm).

The results of the test were as follows: 24% of the students

(6 of them) prefer to study based on seeing—the visualists, 36%

(9 students) prefer to study by listening—the auditory, and 40%

of the students (10 of them) prefer to study by practical activity—

kinesthetic.

Based on this, the students were divided into three groups

(V—visualists, A—auditory, K—practical).

Based on three types of testing, it is interesting to note that

the results of the students on tests were mainly coherent to their

affinities expressed through preliminary testing. The following

graph demonstrates this:

The testing showed that the system described in this

article proved to be accessible to the three groups of students.

Students were graded with the mark from 5 to 10. The results of

Figure 6 Web application—the fifth part.

6 JOVANOVIC ET AL.

the testing are illustrated in Table 1 and in the following

graph:

The metric characteristics of these tests are: reliability,

validity, objectivity, and discriminatoriness. Besides this, these

kinds of tests are characterized by an equal working time and the

same working regime—less time for examination, exactly

determined range of knowledge needed for a certain grade, an

equal dominance of all course parts, the influence of the luckiness

and coincidence factor reduced to a minimum.

Knowledge assessment through computers has been carried

out in schools in the last few years and it has proved to be very

successful. Most importantly, the disadvantages of the teacher as

Graph 2

Graph 1


Figure 7 Web application—the sixth part. (a) Network topology 1 and (b) network topology 2.

8 JOVANOVIC ET AL.

an assessor are eliminated (the same criteria of assessment for all

students). Statistics has shown that students’ success has a

tendency to grow. The data also show a quantitative and

qualitative progress in the sense of the increase in the number

of students who have passed an exam with very good grades.

CONCLUSION

In this article, the Web-based system is presented, the purpose of

which is learning practical aspects from IT area. The system

enables the user, with an access to the Internet, to study, to

accomplish laboratory practice and test the knowledge he/she has

obtained.

In order to offer the possibilities of contemporary testing to

our students as well, the creating system has been experimentally

conducted at a school. The system provides learning contents and

methods suitable for the learners of different learning

styles. Experimental results on the system show that the

system can establish an individualized learning environment

which will improve the efficiency of learning. Also, the

experiment has shown that in our circumstances it is possible to

implement testing by applying IT and logic of computerized

adaptive testing and to open the doors to further research and

perfection.

The system is realized in Java. Primary requests for the

development environment have been the supporting of all

facilities of the IP networking as well as to minimize the cost.

A zero cost environment based on Java has been used. Major

characteristics of Java such as hardware independence,

internal security, and network-based environment compel the

use of Java environment as quite promising. Java is the

predominant language used for Web-based system because of

its portability, reusability, object orientation, and graphical

capabilities. This system is 100% pure Java, and Java is an

interpreted language. This limitation becomes apparent as the

number of simultaneous users and the number of active

components grows, as manifested by many students accessing

our educational system or a full-featured educational system. In

fact, most of students’ complaints about system performance

were about time responses from the server side. One solution

under consideration is the optimization of the server modules

based on a combination of native and Java code. Presently, we are

carefully profiling the system to be able to select the best

combination possible.

REFERENCES

[1] N. Jensen, S. Seipel, and G. Voigt, Heuristic evaluation of a virtual

lab system, Technical Report L3S Q4 2003, VASE 3, L3S,

University of Hanover, Germany, 2003.

[2] M. Alfano, B. Lenzitti, and R. Versace, On-lab: Aweb environment

for on-line labs development, CompSysTech 2005, IV.3-1�IV.3-6.

[3] I. Stiubiener, W. V. Ruggiero, R. M. Silveira, I. Korolkovas, S.

Skopp, and C. Meiler, NETLAB: A framework for remote network

experiences, IEEE Frontiers in Education Conference, 2006.

[4] A. Weyland, E. Kurt, T. Braun, and F. Baumgartner, Virtual routers:

A tool for networking research and education, ACM Comput

Commun Rev 33 (2003), 145�151.

[5] J. Djordjevic, B. Nikolic, and A. Milenkovic, Flexible Web-based

educational system for teaching computer architecture and

organization, IEEE Trans Educ 48 (2005), 264�273.

[6] M. Duarte, B. Butz, S. Miller, and A. Mahalingam, An intelligent

universal virtual laboratory (UVL), IEEE Trans Educ 51 (2008),

2�9.

Figure 8 The realized results statistics.

Table 1 The Results of the Testing

Five Six Seven Eight Nine Ten

Visual 0 0 0 2 2 2

Auditory 0 3 3 2 1 0

Practical 0 2 3 2 2 1


[7] P. Falstad’s, Math and physics applets, http://www.falstad.com/

mathphysics.html.

[8] Virtual labs: curves & surfaces, http://www.math.tuberlin.de/

geometrie/lab/curvesnsurfaces.shtml.

[9] P. J. Moriarty, B. L. Gallagher, C. J. Mellor, and R. R. Baines,

Graphical computing in the undergraduate laboratory: Teaching

and interfacing with LabVIEW, Am J Phys 71 (2003), 1062�1074.

[10] Web laboratory for computing and informatics, Demo Version,

http://weblab.vpskp.edu.rs/mreze/index_e.htm.

[11] N. Jovanovic, R. Popovic, and Z. Jovanovic, WNetSim: A web-

based computer network simulator, Int J Electr Eng Educ 46 (2009),

383�396.

[12] G. Fleming, Learning styles: Know and use your personal learning

style. Available at: http://homeworktips.about.com/od/homewor-

khelp/a/learningstyle.htm

BIOGRAPHIES

Nenad M Jovanovic is a professor in the

Department of Computing and Informatics at

the Advanced Business School in Blace. His

research interests include computer network,

simulation and educations sistems. He received

a BSc in computer engineering from the

University of Pristina, a MPhil from the

University of Belgrade and a PhD in computer

science from the University of Pristina.

Ranko Popovic is an Associate Professor of

Computer Science at Singidunum University,

Serbia. He received his Diploma (M.Sc.) in

Electrotechnics at University of Nis and his

Doctorate (Ph.D.) in Computer Science at

University of Pristina., in 1988 and 1996,

respectively. Since 2007 he has been with

Singidunum University. He has taught many

courses on computer science and authored a

few books in Serbian on the same subject. His research interests

include operating systems, computer networks, distributed systems,

graph theory, multimedia, and distance learning.

Suzana Markovic is a Professor of Computer

Science at Adavanced Buissines School of

Blace, Serbia. She received his BS degree in

Electrotechnics at University of Pristina and

her MS in Computer Science at University of

Belgrade. Her research interests include dis-

tance learning systems.

Zoran Jovanovic is a researcher in the

Computer And Informatics Department at the

Adavanced Buissines School---Blace, Serbia.

He received his MS in Computer Science at

Singidunum University, Serbia. His research

interests include computer netvorks and dis-

tance learning.

10 JOVANOVIC ET AL.

web laboratory for computer network

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