Session T4C INFRASTRUCTURE AND TOOLS FOR A COMPUTER NETWORK AND DATA COMMUNICATION LABORATORY FOR A COMPUTER ENGINEERING UNDERGRADUATE COURSE Graça Bressan1 , Marcus V. S. O. Paula 2 , Tereza Cristina M. Carvalho3 , Wilson V. Ruggiero4 Abstract This project aims at the design of a classroom environment and the development of laboratory experiments for a discipline on Computer Network Laboratory for an undergraduate course on Computer Engineering at Escola Politécnica da Universidade de Sao Paulo. Special consideration was taken concerning the cabling and the planning of the physical and logical configuration of the classroom network, due to the need to run experiments using network equipment like routers and ATM switches. An important part of the laboratories is to reinforce the concepts acquired in the theoretical lectures and, for this reason, the experiments were planned for every network layer. Most of the experiments use software tools specifically developed for the experiments, like runtime libraries and simulators. Besides, the course material profits from tools developed for web distance learning training, including multimedia, on-line evaluation tests, chats and simulators. The laboratory has been running for three years and a new revision of the classrooms and of the experiments is being implemented. Index Terms Computer engineering, computer networks laboratories, undergraduate course.
OBJECTIVES The goal of this project is to implement the classroom environment and to develop laboratory experiments for a discipline on Computer Network Laboratory for an undergraduate course on Computer Engineering at Escola Politécnica da Universidade de Sao Paulo, Brazil. The goals of the discipline Computer Network Laboratory are: • To reinforce the theoretic concepts of computer networks presented in two previous one-semester disciplines on computer networks. • To give students practical experience in aspects of networks such as cabling, management, configuration, network application development, protocol understanding and development. • To allow students to approach some commercial products. 1 2 3 4
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To give professors a feedback on the theoretic disciplines preceding the laboratory work.
HISTORY This project has taken place at LARC - Laboratory of Computer Network and Architecture - and started in 1997. So far, nearly 200 students have been trained. Before that, the Computer Network Laboratory consisted in the implementation of the TCP protocol using C language. This first attempt showed the necessity to have a set of experiments considering all aspects of computer networks, from communication equipment and cabling to network application development. An important role of laboratory experiments is to review and to apply the concepts acquired in the theoretical lectures and, for this reason, experiments were planned for every network layer. Part of the experiments consists in network equipment configuration and, in this case, students have contact with commercial products. The experiments have been reviewed every year. Another issue was to define and build the classroom environment, for 20 students each, with microcomputers connected to a network. Special consideration was given to cabling and the planning of the physical and logical configuration of the network, due to the need to run experiments using network equipment like routers and ATM switches. On December 2000, after 9 groups of students had been trained, it was time for a complete review of all the experiences and the necessary rebuilding of the infrastructure, based on the feedback of these previous groups of students. Some old experiments were discarded and new ones were developed, according to technology evolution. Now the new version of the laboratory course is being applied, consisting of 12 experiments covering subjects from the physical layer to the application layer.
Graça Bressan, Universidade de São Paulo, Escola Politécnica, LARC, Cidade Universitária, São Paulo, SP, Brasil,
[email protected] Marcus V. S. O.. Paula, Universidade de São Paulo, Escola Politécnica, LARC, Cidade Universitária, São Paulo, SP, Brasil,
[email protected] Tereza Cristina M. Carvalho, Universidade de São Paulo, Escola Politécnica, LARC, Cidade Universitária, São Paulo, SP, Brasil,
[email protected] Wilson V. Ruggiero, Universidade de São Paulo, Escola Politécnica, LARC, Cidade Universitária, São Paulo, SP, Brasil,
[email protected]
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Session T4C NETWORK LABORATORY STRUCTURE AND CONCEPTS This laboratory discipline is preceded, in the curriculum, by two one-semester theoretic disciplines: Computer Networks and Data Communication. The laboratory discipline must thus review and practice the concepts learnt in the previous semesters, complementing them and presenting the students a view of practical applications and commercial equipment. Also, a careful observation of the students ' behavior and their performance while executing experiments may indicate gaps in the structures of the theoretic disciplines. Observing the way authors like Stallings[6], Comer[5], Raj Jain [8] and Tanenbaum[7] present network concepts, and analyzing network-training material prepared by network companies like Cisco and 3COM, the authors decided to structure the concepts as: Network Technology, Network Interconnection, Protocols and Application. The laboratory experiments are structured according to the following items: • Network Technology o Network equipment and concepts o Structured cabling o Ethernet, Fast Ethernet and Gigabit Ethernet o ATM • Network Interconnection o Internet protocols o Routers and Routing • Protocols o TCP • Applications o Client-Server applications (developed in 2 classes) o Web applications o DNS o Network Security o Servers management
LABORATORY INFRASTRUCTURE The laboratory infrastructure consists of the physical structure of the classroom, as well as the hardware and software necessary to execute the experiments. To present the theoretic introduction to the laboratory and other kinds of materials, the professor has a microcomputer available in his/her workbench, connected to the same environment the students are using. For good development of laboratory experiences, the classroom must hold no more than 20 students and each experience is performed in groups of two students sharing a computer or equipment. In this situation, the professor and the instructor can follow the work of each group. Therefore, the laboratory classroom has 11 workbenches, 10 of them for each group of two students.
One workbench is reserved for the professor for demonstrations to students. Each workbench is equipped with a PC microcomputer, with ATM and Fast Ethernet cards, connected to a local network using these cards. The workbench computers, configured with dual boot, have Linux Red Hat 6.2, used to run server applications, and Windows NT 4.0 for applications requiring user-friendly graphics. Each workbench has 4 network outlets and 4 electrical outlets for the stabilized electrical circuit supplying power to the microcomputer, network equipment and other equipment used in the experiments. The 4 network outlets of each workbench are identified by numbers and colors and they are part of a structured cabling CAT 5e, shown in Figure 1, developed to connect the workbenches to the network equipment. The cabling connects the workbenches to a rack that holds the patch panels and the network equipment used in the experiments. The function of each workbench outlet is defined by means of interconnection in the patch panels.
FIGURE 1 W ORKBENCH OUTLETS WITH COLOR IDENTIFICATI ON AND P ATCH PANEL OUTLETS WITH COLOR IDENTIFICATION
The room counts on air-conditioning to keep the temperature well suited for people and equipment. Since the purpose of the course is to prepare future engineers, some of the experiments are performed as projects, similarly to what they will meet in future jobs. For this reason, the room has a library of manuals and handbooks on equipment and cabling components, allowing the students to have an updated vision of new equipment and industry future directions. Most of the experiments use software tools specifically developed for the experiments, such as runtime libraries and simulators. These software tools include a library of simulators of IP layer and software to work with sockets. The course also profits from tools developed at LARC for web distance leaning training [1][2], including multimedia material [3], on-line evaluation tests [4], chats and simulators.
EXPERIMENT ACTIVITIES To attain the desired goals of the experiments, and considering that the experiments deal with details of very
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Session T4C diverse themes relating to different equipment and technology, the participation of an instructor to give technical support to students was deemed necessary. Every experiment has a different instructor with specific knowledge and skills. The instructors are students of the master degree program at Escola Politécnica, and they have full knowledge of the experiment material and of the equipment and tools to be used. They collaborate in the preparation of the handouts for the experiences, in the development of software tools and in the configuration of the environment necessary to run the experiments. Some days before the laboratory execution, students must download the document describing the experiment from the home page of the discipline. The laboratory document consists of the theoretic material of the experiment, the directions students must follow to execute the laboratory activities, questions that must be answered beforehand and the structure of the report that must be prepared at the end of the experiment. The laboratory home pages also include other kinds of on-line material. For instance, the theory presentation of the experiment may be available as on-line presentation including video, simulation, animation and multiple-choice tests working as self evaluation. Each experiment is organized in the following basic activities: 1. Preparation: Students must read the theoretic content of the document describing the experiment before the class starts. During the class, students must have a clear view of the activities that will be developed. 2. Initial Evaluation: At the beginning of the class, the students are asked to fill a short evaluation form regarding important aspects of the experiment that will be observed during the practice. They are to spend no more than 10 min in this activity. 3. Execution: During the class, students participate in practical activities such as equipment configuration, programming, measurement and observation. 4. Report: During the experiment, students must prepare a report presenting the main observations, measurements and conclusions regarding the experiment. This report is evaluated considering the critical sense of the students and qualitative vision of the experiment. The laboratory experiment is planned to be accomplished in one 3:30-hour class - or in sequences of two or three classes. The experiments are executed in groups of two or three students coordinated by the professor and supported by the instructor. The result of the experiment includes the report and may include programs or some other material developed during the experiment. In the evaluation of the results obtained by the group of students , the success of the experiment execution, the report of the experiment and other results are considered. The individual evaluation of a student considers:
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the preparation of the experiment by the student; the punctuality of the student to the class; the participation of the student in the activities of the group in the class; the evaluated results of the group.
EXPERIMENTS The laboratory discipline consists of 12 experiments, developed in one class each, unless more time is needed, according to the following themes: 1. Network equipment and concepts 2. Structured cabling 3. Ethernet, Fast Ethernet and Gigabit Ethernet 4. Internet protocols 5. TCP (a project developed in 3 classes) 6. Routers and Routing 7. ATM 8. Client-Server applications (developed in 2 classes) 9. Web applications 10. DNS 11. Network Security 12. Servers management Network equipment and concepts This experiment was planned to introduce students to the practical world of networking. In that way, it is a group of demonstrations of different kinds of network equipment, their functions, their characteristics and their differences. Some concepts presented are: network topologies, network management, broadcast domain, collision domain, routing, difference between hubs, routers and switches, switches and router tables and use of cross cable or direct cable. Structured Cabling This experiment was planned to introduce students to the fundamentals of structured cabling. In this experiment students crimp UTP cables, to learn more about cable technologies, connector types and structured cabling and planning considerations. To consolidate these concepts , students should design the structured cabling for a small building. Ethernet, Fast Ethernet and Gigabit Ethernet This experiment was planned to present the main concepts involved in Ethernet technologies such as Ethernet, Fast Ethernet and Gigabit Ethernet. With it students are led to know mo re about Ethernet, Fast Ethernet and Gigabit Ethernet frame format, medium access and protocols.They should also understand codification differences and standards.
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Session T4C Internet protocols
Web Applications
This experiment was planned to consolidate the main concepts involved in IP protocol such as net and subnets, mask, routing, addressing and other IP concepts, as well as to present ARP, RARP, ICMP and IGMP purpose and protocols. The experiment consists in the use of tools for IP monitoring.
This experiment was planned to introduce students to the Web programming paradigm. They are introduced to some concepts such as Web system architecture, Web Server, CGI, ASP, PHP, JavaScript, HTML, database relational servers, SQL and ODBC drivers. To make these concepts clear, students implement a sample of a Web application using Microsoft ASP pages and ODBC interface to access a SQL Database. The application keeps control of a car stock on the web, permitting inclusion, exclusion and updates of car attributes. For the experiment, they have to configure a Web Server, to create an SQL data base and to configure an ODBC driver.
TCP TCP protocol experiment is the most difficult experience and a very important one. In this experiment students should understand some very important TCP concepts, like TCP ports, TCP flow control, sliding window, state machine and sequence control. To make this clear, they implement a simple version of the protocol TCP over an IP simulated layer. This IP simulated layer is supplied by a library of functions developed to support this experiment. Routers and Routing This experiment was planned to introduce students to the fundamentals of routing and routing protocols as OSPF and RIP. Students are led to understand them through router configuration using static tables and dynamic tables with OSPF and RIP protocols. Students are organized in groups and each group configures a router. The students groups are oriented to work together in such way that communication among all machines is established only when all the groups succeed in the configuration. ATM This experiment was planned to introduce students to the ATM network technology. Some concepts presented are: LES, LEC and ATM addressing, Classical IP and LAN Emulation. Students are led to configure an ATM switch and ATM NIC, presenting measures of the network performance. Client-Server Applications This experiment was planned to introduce the students to Client-Server concepts. They are presented to some concepts such as client applications, server applications, server sockets, client sockets, HTTP protocol and SMTP protocol. This experiment consists in the implementation of a Web Server using Java language using socket interface. This experiment is carried out in 6 hours, divided in two days. Using a commercial browser, students send requests to the implemented Web Server. Its is a great moment of joy for students when the browser receives a document with text, pictures and many multimedia objects sent by the Web Server they have just implemented.
DNS This experiment was planned to present the DNS purpose, application and importance to students . With it they learn concepts such as : DNS functions, DNS name translation, DNS protocols, DNS zones, DNS reverse translations and DNS security. To make these concepts clear, students are led to configure a DNS server in Linux platform and test its functionality in the network. Network Security This experiment was planed to present the main security concepts to students . They learn concepts such as symmetric and asymmetric cryptography, firewalls, proxy, NAT (network translate address) , intrusion detection and types of attacks. To make these concepts clear, students are led to configure a Firewall, play cryptography simulations on the web and configure proxy and NAT services. Servers Management This experiment was planned to introduce the students to the main concepts involved in configuring a server and the main services of a network. The students are led to configure a Linux server with DNS, Web and Ftp services. After that, they perform some tests to verify the integrity of the configuration.
UNSUCCESSFUL CASES During the three years the laboratory discipline was running, some experiments that did not work well were discarded. One of them was an experience designed for the student to work at link level using an Ethernet emulator. This emulator consisted of a very simple hardware connecting two serial ports of a microcomputer, so that both ports could send and receive at the same time, generating a collision. Besides , each port could rear what it had sent. Transmission errors were simulated by a function that inserted noise in the
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Session T4C transmitted data. This laboratory was planned for two 3:30hour work days. The student had to design the software to transmit a file using a stop-and-wait protocol, detecting collision and transmission errors by a CRC 32 and retransmitting the missing data. The experience did not work as planned because students were losing much time designing codes to deal with transmission of data through serial port, before implementing the protocol, which was the most important part of the experience. Only part of the students succeeded in reaching the end. It was possible to improve the experience to reduce implementation time but, as there were other experiences with more important and useful concepts, this experience was replaced by another one.
FUTURE STEPS – EVOLUTION We see the evolution of the laboratory in four directions: the continuous adaptation of old experiments; the creation of new experiments; the improvement of the infra structure of the lab and the evolution in the experiments format . The continuous adaptation of old experiments Every experiment should always be improved. There is always something to be done to make it easier, richer and more understandable.
RESULTS
Creation of new experiments
At the end of the semester, the feedback provided by the students, assures that the intended goals of the discipline were reached. In general, the students have a good opinion as the discipline contributed to reinforce the theoretic knowledge and prepared them to work in practical fields demanded by future jobs. The TCP project is the most complex experiment of the networks laboratory. After some groups had been trained, students were observed to spend about 40 hours in home activities and only 15% percent could complete 100% of the work. About 70% completed about 80% of the program and 15% completed less than 50%. Although not 100% of the students complete 100% of the work, more than 95% can assuredly understand concepts that were not clear with theoretical classes alone. These results confirm previous expectations that a deep understanding of network protocols should be approached in a practical way. Another important consideration is that all the experiments mentioned here had to be changed one or more times to achieve a good format. It can thus be observed that it is not easy to create a practical experiment since the way students will react is unpredictable until the test. Regarding students’ behavior, it was observed that they sometimes have a biased view that it is important to acquire, in undergraduate disciplines, all the knowledge necessary to work in a future job, mainly information about specific products commercially available. The importance of some products is acknowledged; however, it is not the purpose of this discipline to present products but the technology behind them. Based on the fact that technology, mainly in computer networks, changes extremely quickly, the authors believe that it is not wise to consider only the demands of the market but to give attention to theoretic and basic knowledge and open standard rules. On the other hand, it is not wise to consider only classical network knowledge during the class. It is always necessary to motivate students with new technologies. The objective thus is to reach a balance between basic concepts and practical knowledge.
In the network area , new technologies are always presented. One of our goals is to maintain our students updated with new technologies. Therefore new exp eriments should continuously be created with new themes and new formats. Some of the new themes suggested are: Last Mile Technologies, Wireless networks, charge balancing, multimedia networks, simulations. Evolution of the infra structure of the laboratory To keep the experiments on time with new technologies and new educational practices, the laboratory infra-structure should continuously be updated. This means to continuously renovate network equipment, computers, software and tools. The evolution on the format the experiments are presented Web format is a learning framework that will help in many aspects , e.g. the student can do tests on web; all the material for experiments became easily available to use and access.
CONCLUSION After three years running this laboratory discipline, when more than 150 students were trained, it can be concluded that: • Networking knowledge should be introduced with both theoretical and practical approach. • Practical experiments should always have an engineering approach with activities that rise curiosity and that challenge students so as to provide motivation. • It is very hard to achieve a perfect format for an experiment. It should always be improved and updated. • It is essential to have good infra-structure. • The experiments material should always be clear about the goals and expectations of the practical activities. • A practical course should always motivate students with new technology experiments. One way to achieve this
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Session T4C goal is to give them a view of where and when those concepts are useful in real life.
ACKNOWLEDGMENTS During the time the laboratory experiments were developed and executed, many people provided important contribution: engineers Oscar D. Vilcachagua, Denis Gabos (Phd.), Cíntia B. Margi (Msc.), Stephan Kovach (Msc), Fernando Redigolo (Msc.), Marcelo Blanes, Fernanda R. Spinardi, Luís H. B. Ceze, Karin Strauss, Leonardo A. Martucci, Leonardo R. Bachega, George M. M. A. Smetana , Pedro A. L. Mindlin, Allison Veras (engineering student).
REFERENCES [1]
Margi, C., B., Vilcachagua, O., D., Stiubiener, I., Silveira, R., M., Bressan, G., Ruggiero, W.,V. “An On-line Web Course Environment and Its Application”, Proceedings of IEEE-Frontiers in education: Building on a Century of Progress in Engineering Education, Kansas, 2000.
[2]
Bressan, G., Silveira, R., M., Ruggiero, W., V., “A Framework for Distance Learning Employing Video on Web Environment”, Proceedings of International Conference on Technology and Distance: Building Bridges through Technology and Distance Education, Fort Lauderdale, Nova Southeastern University, 1999.
[3]
Silveira, R. M. Margi, C. Gonzalez, L. A. G. Favero, E. Vilcachagua, O. D. Bressan, G. Ruggiero, W. V. “A Multimedia on Demand System for Distance Education”, Proceedings of International Conference on Technology and Distance: Building Bridges through Technology and Distance Education, Fort Lauderdale, Nova Southeastern University, 1999.
[4]
Vilcachagua, O., D., Favero, E., Bressan, G., “Sistema Modular de Avaliação da Aprendizagem Via WEB”, Anais do VI Congresso Internacional de Educação à Distância , ABED. São Paulo, 1999.
[5]
Comer, D.,"Internetworking with TCP/IP: Principles Protocols and Architecture", Vol I, 4rd Ed., Prentice-Hall Inc, 2000.
[6]
Stallings, W., "Data and Computer Communications", 5th ed., MacMillan Publishing Company, 1996.
[7]
Tanenbaun, A., "Computer Networks", 3rd ed., Prentice-Hall, 1996.
[8]
Jain, R., Laboratories for Data Communications and Computer Networking, Department of Computer and Information Science, Telecommunications Research Lab, http://www.cis.ohiostate.edu/~jain/cise.
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