Networks

COMPUTER NETWORKING LABORATORY PROJECTS*

Guillermo A Francia, III Chi Chin Chao Jacksonville State University Mathematics, Computing, and Information Sciences Department 700 Pelham Rd North Jacksonville, AL 36265 {gfrancia, cchao}@jsucc.jsu.edu A

ABSTRACT The formidable task of not only trying to balance application and theory but also to keep up with the rapid advancement in technology is always upon Computer Science mentors. This paper presents a series of laboratory project descriptions that are used in a laboratory model for a curriculum that strives to meet the challenges presented by the rapid advancement of telecommunication technology. These laboratory projects are divided in two main categories: hands-on network configuration and network programming. INTRODUCTION The formidable task of not only trying to balance application and theory but also to keep up with the rapid advancement in technology is always upon Computer Science mentors. The rapidly evolving telecommunications technology presents an ever increasing demand from the industry to better prepare future scientists and technicians who are adept in the field. This paper presents a series of laboratory project descriptions that are used in a laboratory model for a curriculum that strives to meet the challenges presented by the rapid advancement of telecommunication technology. These laboratory projects are divided in two main categories: hands-on network configuration and network programming.

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Copyright © 2003 by the Consortium for Computing Sciences in Colleges. Permission to copy without fee all or part of this material is granted provided that the copies are not made or distributed for direct commercial advantage, the CCSC copyright notice and the title of the publication and its date appear, and notice is given that copying is by permission of the Consortium for Computing Sciences in Colleges. To copy otherwise, or to republish, requires a fee and/or specific permission. 226

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THE CURRICULAR NEED During the past decade, telecommunications have undergone an extraordinary acceleration due to the vast improvement in both the physical and logical structure of computer networks. The physical aspect of this improvement is characterized by the rapid deployment of fiber optic cables, high-frequency channels, infrared media, and ISDN lines. The improvement on the logical side is manifested by the ten-fold improvement of the widely used Ethernet protocol into Fast Ethernet and even by a hundred-fold increase as manifested by Gigabit Ethernet. Coupled with this is the introduction of new protocols such as those that integrate voice, data, and video. This phenomenon entails the augmenting of the traditional curriculum suggested by the 1991 ACM Curriculum [ACM91] withincreased emphasis on technicalskills. Fox and Reynolds best describe this curriculum issue in their Information Technology Curriculum Vision [Reyn96], which calls for the additional pedagogical emphasis on networks, databases, multimedia, and intelligent systems. The increasing emphasis on networking and telecommunications needs in the undergraduate curriculum is clearly seen in the knowledge and learning units of the IS'97 model curriculum [Davi97]. THE LABORATORY PROJECTS The design of the computer-networking laboratory projects is based on the following rationale: •

to provide students a hands-on experience in installing and managing an advanced heterogeneous computer network,

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to provide students a first-hand experience in network programming using Java network Application Program Interfaces (APIs), and

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to be able to apply and/or simulate theoretical networking concepts.

The design of the laboratory projects was influenced by published descriptions of network laboratory projects that appeared in [Fink94, Lank98, Siva99, Smit91, and Toll95]. These projects were directly or indirectly supported by NSF grants and were well received by undergraduates. In addition, excellent network theory and programming materials were adapted from those that were described in [Haro00, Reil02, Darb01, Stev98, and Stev92]. The Hands-on Laboratory Project Activities Activity 1: Basic Wiring and Network Connectivity This activity is divided into two main components: a network hardware configuration part and a network monitoring part. Initially, the students are required to cut, splice, assemble, crimp, and test an unshielded twisted pair (UTP) cable for the hardware component of this activity. Then, with the aid of a cable scanner tool and an Ethernet switch, the students are required to test the hand-manufactured cable for connectivity, length, and integrity.

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For the network monitoring part, the students are required to use the following systems programs: ipconfig, netstat, arp, and an open source software: ethereal. These system tools are used to gather pertinent network configurationinformation. After performing an investigation of various network configurations, the students need to interpret and analyze the collected data. These data are classified into two main classes: static and operational. The static information include, among others, hostnames, IP addresses, hardware addresses, gateway addresses, DNS server addresses, subnet masks, and DHCP statuses. The dynamic or operational information include a) network interface statistics on the number and size of packets sent and received, and b) IP/TCP/UDP statistics on the number of received packets, the number of failed connections, and the number of retransmissions. For both components of the project, the students are required to submit a written report on all the data gathered, the experiences gained, and detailed analyses and interpretations of the results. Activity 2: LAN Setup and Configuration The purpose of this activity is to give students a hands-on experience with configuring a heterogeneous Local Area Network (LAN) using a Linksys EtherFast DSL Router, a Windows 2000 system, an iMac system, an SGI-Irix system, and three (3) Linux systems. The students start by configuring the LinkSys EtherFast device as a router. They are provided with the specific IP numbers, DNS server address, and a gateway address to use. After the router configuration, the host machines are configured individually with some pre-defined network parameters. Upon completion of the test for local connectivity, each machine is tested for Internet connectivity. The students are asked to configure the web browser on each machine for Internet browsing capability. Thus, each machine had to be configured with the proper proxy settings. The final segment of the activity calls for the configuration of the router for some specific functionalities such as enabling IP and MAC address filtering, the blocking of Wide Area Network (WAN) requests, enabling multicasting, establishing VPN sessions by enabling Point to Point Protocol (PPTP) Pass-through, enabling remote management, specifying the Maximum Transmission Unit (MTU), and enabling Quality of Service (QOS) for various ports. The LAN setup is depicted in Figure 1. Finally, the students are required to submit a report that documents detailed descriptions of their work and experiences in the laboratory. In that report, a special emphasis is made on all the difficulties and challenges that they have encountered during the project execution.

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Figure 1. The LAN Setup

The Network Programming Projects Programming Project 1: User Datagram Protocol (UDP) Implementation In this project, the students are required to implement the Trivial File Transfer Protocol as described in Request For Comments (RFC) 1350 [Sol92] using the Java UDP APIs. In addition, the students are required to familiarize themselves with RFC 768 [Post80] before attempting the implementation. The application program consists of two parts: a client and a server. These are to be constructed using the UDPSender and the UDPReceiver classes that are discussed in a class lecture. For the client side, the application uses the Graphical User Interface (GUI) that is shown in figure 2. The server side does not need any user interface and should be designed as a process running on the background. The students are provided with the source code of the GUI implementation and are informed on the functionality of each GUI component. The project description that can be downloaded from the course web site provides further details of the implementation requirements. To test for proper file transfers, the students need to run the program simultaneously on two computers and to perform both file upload and download actions.

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Figure 2. The Client Graphical User Interface

Programming Project 2: Multicast Implementation In this project, the students are required to complete a GUI based peer-to-peer chat room implementation using the Java multicast and UDP APIs. As a background preparation for the assignment, the students are encouraged to perused RFC 1112 [Deer89], the RFC for multicasting. The user interface for the chat room is depicted in Figure 3. The source code, which is mostly that for the GUI implementation, is given to the students in order to jump start their implementation. It is divided into two main classes: the GUI component and the thread component. This setup facilitates the concealment of the GUI implementation details from the student and promotes the independence of the class implementations. The students are instructed that the implementation of the GUI component is complete and their efforts should be concentrated on enhancing the thread class. A code snippet of this class is shown in Figure 4. The students are advised to test their chat room by running it on at least three (3) computers. Each user of the application starts by joining the chat room which is accomplished by specifying the chat group IP address (224.0.0.1) and the port number (4001). The messages are then sent to and from each user to simulate a real-time network instant messaging scheme.

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Figure 3. The Multicast Chatroom Client Graphical User Interface

public void run ( ){ // This method is called by the start( ) invocation in the // constructor method, MulticastThread(String ipNum, int portNum, int TTL). // // It should run indefinitely while the system is in the // Chatroom, thus the code while (isActive) { // Receive the datagram and post it on the //TextArea window. // Hint: to be able to manipulate the TextArea // window, you need to use the // accessor method, getJTxtArea( ) and the // mutator method, setJTxtArea( ). Both of // these are // methods of the MulticastChatGui class. }//end of while }//end of run public void sendMsg(String msg, String ipNum, int portNum){

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// This method is called by the event of the mouse click // on the send message button in the GUI. // Its function is to package the message using a Datagram // packet and send it to the multicast socket. }//end of sendMsg

Figure 4. The Multicast Thread Source Code Snippet Programming Project 3: TCP/IP Implementation The last project involves a TCP/IP implementation of a network game. The students are required to complete a GUI based implementation of a TicTacToe game over the network using the Java TCP socket APIs. The students are encouraged to be familiar with RFC 793 [Post81]

Figure 5. The Game Interface Window before starting this project. The graphical user interfaces are depicted in Figures 5 and 6. The GUI displays the TicTacToe board and provides manual entry for data that is required by TCP communication. Before the start of the game, a player selects a game piece

Figure 6. The Message Dialog Notification Window 232

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(an O or an X) and enters the remote IP address and port number needed for communication. The game is started by clicking on the Start Game button. Figure 6 depicts a message dialog window that pops out as soon as a game winner is determined. A source code for this project is provided to help the students get a quick start on their implementations. This assignment, which is comparable to the previous project, has two (2) main class implementations. However, this project requires a more elaborate implementation and the completion of both classes. The first class, TicTacToeGUI, is a semi-complete implementation of a GUI based TicTacToe game using the Java Swing APIs. The methods that need to be completed on this class are: the checkWinner( ) and the showMove( ) methods. The code snippet for both is shown in Figure 7. public static int checkWinner(){ // Parameter: none // Return: 0 if O wins, 1 if X wins, 2 if no winner // CS450 Students: // You need to complete this method. Here is the // general description of its functionality: // This method checks the rows, columns, and diagonals // of a matrix,called table[][] to determine whether a // player has won the game. // Note that each cell in table[][] is initialized to // 2 (unoccupied)and either to a 0 or a 1 depending on // whether O or X is placed in there. This method is // invoked by the showMove() method. }//end of checkWinner public static void showMove(int cellIndex, boolean myMove){ // Function: This method sets the an icon (either an // X or an O) on the board. // Input: cellIndex - the index number of the cell // that is affected on the board. Note that the // cells are numbered according to the ffg: // 0 1 2 // 3 4 5 // 6 7 8 // myMove - a boolean value which indicates // whether the move was made by the // local player (true) or the // the remote player (false). // Return: none // The algorithmic steps are as follows: // 1. Calculate the row and column values of the // table using the cellIndex. Note that the // matrix, table[][], needs to be set to 0 or 1 // depending on whether an O or an X is placed // in its corresponding board cell. Here are some // sample scenarios: if an X is placed in // cellIndex 0, table[0][0] must be set to 1. // If an O is placed in cellIndex 7, then // table[2][1] must be set to 0.

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// // 2. Check who made the move. Thus, // if (myMove) { //it is a local move // // ............ omitted code snippet in here. Check the // source supplied for the omissions! }//end of showMove

Figure 7. The Code Snippet for the TicTacToeGui Class The second class implementation, TCPThread, extends a Thread class. This class has been stripped of some important code implementation of a client-server TCP communication. The students need to complete the methods, run( ) and sendMsg( ), in order to make it functional. The specifications for these methods are shown in the code snippet in Figure 8. public void run (){ // This is the method that is called when a thread // initiates a start while (isActive) { try { //Listen for a connection....on the server //socket and connect to a buffered reader // Parse the received buffered steam into chunks // of integers and save it into a string of // characters called msg. //trim the message out of unprintable //characters: //invoke the static method of the TicTacToe //class called showMove() to display the selected //move of the remote player. Note that this //method requires 2 parameters: the msg converted //to an integer value which will correspond to //the cellIndex and the boolean //value, false,to indicate that this is a remote //player's move. //close the socket. }//end of try catch (SocketException se){ System.out.println("Socket Exception : " + se); } catch (IOException e) { System.out.println("Exception : " + e); }//end of catch }//end of while }//end of run public void sendMsg(int cellIndex){ try {

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//connect to an InputStreamReader and a //BufferedReader // create a socket and connect // create the message string using the value of the // cellIndex // set the sendBufferSize to the message length // create a bufferedOutputStream and send the message // to the bufferedOutputStream character by character //close the bufferedOutputStream //close the socket }//end of try catch (Exception e) { System.out.println("Exception: " + e.getMessage()); }//end of catch }//end of sendMsg

Figure 8. The Code Snippet for the TCPThread Class The students are advised to test their implementations by running the application on two (2) computers and play a game of TicTacToe! CONCLUSION and FUTURE WORK Finding the appropriate balance between theory, practical experience and research is difficult in all computing courses. [ACM91, Davi97, and Lank98] This is especially true in the areas of networking and computing systems. This paper outlined the laboratory projects that are currently being utilized to support courses in these areas. The activities and projects are designed and structured to provide practical experiences while illustrating theory and possible research areas. The challenge for the authors will be in the continual development of these activities and the introduction of novel activities and projects that will leverage the availability of state-of-the-art networking facilities. Future work will include: • wireless protocol implementations, • network security design activities, • an implementation of a functionalweb server using the HyperText Transfer Protocol (HTTP), • an implementation of an electronic mail facility using the Simple Mail Transfer Protocol (SMTP), • wired and wireless benchmarking projects, and • data encryption implementations. 235

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ACKNOWLEDGEMENTS This paper is based upon a project partly supported by the National Science Foundation under grants DUE-9950946 and DUE-0125635. Opinions expressed are those of the authors and not necessarily of the Foundation. REFERENCES [ACM91] Computing Curriculum 1991. Report of the ACM/IEEE-CS Joint Curriculum Task Force. ACM Press. 1991. [Darb01] Darby, C., et. al. Beginning Java Networking. WROX Press Ltd. Birmingham, UK. 2001. [Davi97] Davis, G., et al., IS'97 Model Curriculum and Guidelines for Undergraduate Degree Programs in Information Systems. 1997. [Deer89] Deering, S. "Host Extensions for IP Multicasting," RFC 1112. Website: http://www.rfc-editor.org. 1989 [Fink94] Finkel, D. and Chandra, S. NetCP-A Project Environment for an Undergraduate Computer Networks Course. SIGSE Bulletin, Vol 26 No. 1, 1994. [Haro00] Harold, Elliotte R. Java Network Programming. O'Reilly & Associates, Inc. Sebastopol, CA. 2000 [Lank98] Lankewicz, L., Resources for Teaching Computer Networks. The Proceedings of the Twenty-ninth SIGCSE Technical Symposium on Computer Science Education. Atlanta, GA, 1998. [Post80] Postel, J.B. "User Datagram http://www.rfc-editor.org. 1980.

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[Smit91] Smith, W.D. The Design of an Inexpensive Undergraduate Data Communications Laboratory. SIGSE Bulletin, Vol 23, No.1, 1991. [Sol92]

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