DEVELOPMENT AND APPLICATION OF A NEW CURRICULUM FOR COMPUTER NETWORKING Presenter Xiaolong Li, Assistant Professor Department of Industrial and Engineering Technology Morehead State University Gabriel Alungbe Department of Industrial Engineering &Technology Morehead State University Yuqiu You, Department of Industrial Engineering &Technology Morehead State University This paper describes a course and laboratory of computer networking for students in the Department of Industrial and Engineering Technology (IET) at The Morehead State University. INTRODUCTION Computer networking is a fundamental course for Electrical, Electronics & Computer Technology Program (EECT). Teaching computer networking course for EECT students can be a challenge because of the breadth of topics spanning from electrical engineering to computer engineering and computer science which encompasses concepts from physical layer such as bandwidth, modulation, and coding to application layer such as DNS and DHCP. In our computer networking class, we set up a weekly lab which accounts for the same amount of time as the lecture. The outcome of this curriculum is to have students benefit from a better understanding of fundamental concepts as well as gaining hands-on experience. In this paper, we show how we use network equipments and network analyzers to develop this new curriculum. In the past, our department has purchased networking equipment such as Cisco switches and routers to establish the networking lab. However, we have faced the problems that only limited topics can be explored through these equipments. For most students in my department, they can understand better the topics if they can see how they work. Ethereal is one of such software that can provide the sequence of messages exchanged between two protocol entities so that students can see network protocol in action. The Ethereal labs are good for students to investigate every part of the network. However, Ethereal cannot provide students with hands-on experience on how to configure and maintain router and server. Therefore, we designed 9 labs on router and server configuration and maintenance. However, the scope of the lab topics with router and server are limited, such as we only have 100Mbps cable so that we cannot investigate the performance if the 100Mbps cable is substituted by 1Gbps cable. Recently, I found the OPNET IT Guru simulator can be used for evaluation of network design. OPNET is a very powerful network simulator. It provides network modeling, simulation, and analysis. It has been widely used for research and professional network design. With OPNET, engineer and system administrator can very effectively analyze the system performance, diagnose problem, and validate changes before they are implemented. However, it is also very, very expensive. Fortunately a limited (at no cost) academic version OPNET IT Guru Academic Edition exists that is good enough for our labs. In this curriculum, I developed two labs which require students to use OPNET IT Guru Academic Edition to design and validate a network.
Therefore, in this curriculum, I use Ethereal, OPNET IT Guru, Cisco Switch, Cisco Router, and Linux to develop 15 computer networking labs so that students will better understand the concepts of framing, encapsulation, and protocol as well as know how to implement, manage, and analyze a networking design configuration and maintenance of router and server. The lecture mainly focuses on the concepts, principles, and protocols on computer networking. The textbook that we adopted is Andrew S. Tanenbaum s Computer Networks, 4th edition [1]. Students attending both lecture and lab will obtain better understanding of the fundamentals of data transmission, internetworking protocol, and network security and gain the skills to design and analyze computer networking, configure and maintain network switches and routers, and install and maintain network server. This paper will describe the labs with feedback from students. The main goals of the labs are to: To understand the concepts of layer To understand the concepts of encapsulation and framing To gain skills on conducting network design and evaluation. To gain hands-on experience on configuration and maintenance of switch, router, and server. To gain skills on trouble shooting ETHEREAL Understanding of the concepts on layering, encapsulation, and protocol can often be greatly deepened by seeing protocol in action and by observing the sequence of message exchanges between two protocol entities, delving down into the details of protocol operation, and causing protocol to perform certain actions and then observing these actions and their consequences. This can be done in a simulated environment or in a real network such as the Internet [2]. The former approach will allow students run various network applications in different scenarios using a computer in the lab. Students will observe the network protocol in the computer in action, interacting and exchanging messages with protocol entities executing elsewhere in the Internet. Ethereal, which has similar functions as tcpdump, is such a tool that can be used to capture and analyze packets in networks. In fact, Ethereal is also used by network professionals around the world for troubleshooting, analysis, software and protocol development, and education. It has all of the standard features you would expect in a protocol analyzer, and several features not seen in any other product. Its open source license allows talented experts in the networking community to add enhancements. It runs on all popular computing platforms, including Unix, Linux, and Windows. The basic tool for observing the messages exchanged between executing protocol entities is called a packet sniffer. As the name suggests, a packet sniffer captures ( sniffs ) messages being sent/received from/by a computer; it will also typically store and/or display the contents of the various protocol fields in these captured messages. A packet sniffer itself is passive. It observes messages being sent and received by applications and protocols running on a computer, but never sends packets itself. Similarly, received packets are never explicitly addressed to the packet sniffer. Instead, a packet sniffer receives a copy of packets that are sent/received from/by application and protocols executing on your machine. The structure of Ethereal is shown in Figure 1 [2]. It has two parts. At the right side are the protocols and applications that run on a computer. In the dashed rectangle is the packet sniffer or Ethereal installed in the computer which consists of two parts. The packet capture receives a copy of every link-layer frame that is sent from or received by the computer. The packet analyzer will display the contents of all fields within a protocol message. In order to do so, the packet analyzer must understand the structure of all messages exchanged by protocol. Ethereal currently supports more than 700 protocols [3].
Figure 1. Structure of Ethereal PEDAGOGICAL DESIGN Our lecture follows the traditional bottom up scheme in teaching networking [1]. We begin with an introduction of computer network; followed by physical layer, data link layer (including MAC layer), network layer, transport layer, and application layer. The idea behind this pedagogical approach is to have students to explore the detail of packet switching networks, such as cabling, fragmentation, routing algorithm, and experience how to build a virtual network and test its performance. We have 15 labs that haven developed to topics from [1] and has been taught in the fall semester 2006 and is taught again in fall 2007. Each lab has 2 hour activities, held weekly for 15 weeks in our networking lab in the IET department at the Morehead State University. LAB EXERCISES Lab 1 Introduction to Ethereal The objective of this lab is to let students know where to get Ethereal, how to install Ethereal, and explore the different functions provided by Ethereal. Students will be asked to capture packets while browsing website and then use Ethereal to analyze the captured packet.
Command menus Line of Captured Packets Details of Selected Packet Header Packet content in hex and ASII Figure 2. Ethereal GUI Figure 2 shows the interface of Ethereal and information of captured packets. Students will be required to explore all functions of Ethereal and give explanations on the captured packets. Lab 2 Using Ethereal to explore encapsulation The objective of this lab is to investigate the Ethernet protocol. Students will be required to review Ethernet and link-layer addressing. Then students will use Ethereal to capture packets. Students need to examine the captured packet to find the source and destination MAC addresses, frame format, frame type, and content of payload. Lab 3 Building a local area networking This lab focuses on the ability to connect two or three PCs to create a simple peer-to-peer Ethernet LAN between workstations with or without a hub or a switch. In addition to the Layer 1 physical and Layer 2 data link connections, the computers must also be configured with the correct IP network settings, which is Layer 3, so that they can communicate. A basic CAT 5/5e UTP crossover cable and straight through cable are all that is needed. Lab 4 Connecting a router This lab will ask students to identify the Ethernet and FastEthernet interfaces on the router; identify and locate the proper cables to connect the router and PC to a hub or switch; configure HyperTerminal to establish a console session with the router; use several basic router commands to determine how the router is configured; and use the router help facility. Lab 5 Configuring a router After this lab, students will be able to identify basic router modes of user EXEC and privileged EXEC; use commands to enter specific modes; become familiar with router prompt for each mode; configure a password for console login to user mode and for virtual terminal sessions; configure a secret password for privileged mode; and configure the router interfaces. Lab 6 LAN configuration In this lab, students will be required to use all their knowledge obtained from lab 4 and lab 5 to build a LAN as shown in the following figure.
Figure 3. LAN configuration Lab 7 Routing and routing protocols In this lab, students will learn how to configure static routes between routers to allow data transfer between networks without using dynamic routing protocols. The network used in the lab is shown in figure 4. The equipment configurations are listed in table I. Table 1. Lab equipment configuration Router Router Name FastEthernet0 Interface Type Serial Serial0 Address Designation Address 0 Router 1 GAD 192.168.14.1 DCE 192.168.15.1 Router 2 BHM 192.168.16.1 DTE 192.168.15.2
Switch/Hub Router 1 Router 2 Straight- Through Cable Rollover (Console) Cable Crossover Cable Figure 4. Network Serial Cable Lab 8 Routing using RIP The objectives of this lab is to set up an IP addressing scheme using Class B networks; configure the dynamic routing information protocol (RIP) on routers; observe routing activity using the debug ip route command; prevent routing updates through an interface to regulate advertised routes; use the passive-interface command and add a default route; gain access to a router with an unknown privileged EXEC (enable) password The network used in this lab is exactly same as lab 7 shown in figure 4. The lab equipment configurations are listed in table II. Table 2. Lab equipment configuration Router Designation Router Name FastEthernet0 address Interface Type Serial0 Address Router 1 GAD 172.16.0.1 DCE 172.17.0.1 Router 2 BHM 172.18.0.1 DTE 172.17.0.2 Lab 9 Basics of OPNET IT Guru Academic Edition OPNET IT Guru Academic Edition enables students to better understand the core concepts of networking and equips them to effectively troubleshoot and manage real-world network infrastructures. This lab teaches students the basics of using OPNET IT Guru Academic Edition, including creating projects, building models, choosing statistics, managing scenarios, and viewing results. Students will be required to follow the tutorial provided by the software. Lab 10 Network Design The objective of this lab is to demonstrate the basics of designing a network, taking into consideration the users, services, and locations of the hosts. Optimizing the design of a network is a major issue. Simulations are usually used to analyze the conceptual design of the network. The initial conceptual design is usually refined several times until a final decision is made to implement the design. The objective is to have a design that maximizes the network performance, taking into consideration the cost constraints and the required services to be offered to different types of users. After the
network has been implemented, network optimization should be performed periodically throughout the lifetime of the network to ensure maximum performance of the network and to monitor the utilization of the network resources. In this lab students will design a network for a company that has four departments: Research, Engineering, E- Commerce, and Sales. Students will utilize a LAN model that allows them to simulate multiple clients and servers in one simulation object. This model dramatically reduces both the amount of configuration work student need to perform and the amount of memory needed to execute the simulation. Students will be able to define a profile that specifies the pattern of applications employed by the users of each department in the company. By the end of this lab, student will be able to study how different design decisions can affect the performance of the network. The network model used in the lab 10 is shown in figure 5. Figure 5. Network model Lab 11 TCP Performance using Different Congestion Control Mechanism In this lab, students will conduct the lab to investigate the congestion control algorithms implemented by the transmission Control Protocol (TCP). Students will study TCP s use of sequence and acknowledgement numbers and they ll look at TCP s receiver-advertised flow control mechanism. They will investigate the performance (throughput and round-trip time) of the TCP connection between the client and the server. Lab 12 Installing an FTP server This lab will let students be familiar with Linux command and be able to configure FTP server. Students will learn how to boot Linux system; how to use Linux command, such as emacs, cp, pwd, ls, netstat, etc. After they are familiar with Linux, they need to learn how to configure a FTP server. Lab 13 Installing DHCP server This lab will deepen the concepts of DHCP application and teach students how to configure DHCP server in Linux. Lab 14 Installing APACHE Running a web server proves a common way in which people expose themselves to an "alternative" operating system known as Linux. We call the web server most commonly used on the web today Apache. It is based on work done at NCSA on the httpd web server. According to a netcraft survey, the Apache web server dominates the market with more than 60% saturation. Students will be required to configure the APACHE server in Linux. Lab 15 Installing SAMBA Samba is a great tool for letting Microsoft Windows users share hard drives and printers with Linux users. With the recent release of Samba 2.2, the Samba team has made major improvements to their server software, including
support for Windows 2000, NT 4.0, and XP clients. Students will become familiar with SAMBA and be able to configure SAMBA server in Linux after this lab. STUDENT FEEDBACK After one run of this course during the fall 2006, we have assessed the educational value of the lab exercises through feedback from students. Our results show that students found that these labs are very interesting and easy to follow. They consider the lab necessary for them to understand protocols, message, and datagram and frame format and they are well motivated by lab exercises. In addition to help students understand the concepts, details of packet formats, and protocols, these lab exercises provide the following main benefits Hands-on experience with switch, router, and Linux Hands-on experience with Ethereal to trouble-shoot and diagnose networks. Hands-on experience on OPNET IT GURU to construct different computer networks and conduct network performance analysis CONCLUSIONS A series of labs has been developed which can let students observe protocols in action, run various networks in a virtual environment, obtain hands-on experience on switch, router, and server. Feedbacks show that these labs can motivate student s interest in networking, help them gain hands-on experience. REFERENCES [1] Andrew S. Tanenbaum, Computer Networks, 4 th Edition, Prentice Hall, 2002. [2] J. F. Kurose and Keith W. Ross, Supplement to Computer Networking: A Top-Down Approach Featuring the Internet, 3 rd Edition, Addison Wesley, 2004. [3] http://www.anheng.com.cn/news/html/wlan_test/ethereal.html, accessed on September 16, 2007.