Enabling Remote Access to Computer Networking Laboratories for Distance Education

Transcription

1 Enabling Remote Access to Computer Networking Laboratories for Distance Education Carlos E. Caicedo Bastidas Syracuse University, Abstract - Academic organizations that provide students with the facilities for experimenting and learning basic and advanced concepts in networking rely on computer networking laboratories. These facilities can be implemented in many ways with varying degrees of cost, management complexity and capabilities. The benefits of these facilities can be extended by enabling remote access to them for distance education purposes. Providing remote access capabilities to these facilities with the objective of offering the learning experience of a computer networking laboratory to distance education students of Information and Communication Technology (ICT) programs is a challenging task. This paper provides a description and a comparative analysis of the implementation of three different computer network laboratory setups for which remote access was enabled and discusses lessons learned and good practices for similar setups. Index Terms Distance education, experiment based learning, laboratory design, laboratory management. INTRODUCTION Computer networking laboratories are a key resource for academic organizations that seek to provide their students with facilities for learning basic and advanced concepts in networking [1, 2]. Providing remote access to a computer networking laboratory for the purpose of extending its educational value to distance education students is a challenging task. Three different laboratory setups are presented in this paper in order to evaluate the infrastructure, management and acceptance characteristics of different laboratory configurations enabled with remote access. These configurations were deployed as part of an initiative to extend laboratory-based activities to distance students enrolled in one of the computer networking courses of an ICT program - the Telecommunications and Network Management program - of Syracuse University (SU). This paper provides a comparison among the different setups that were deployed mentioning their advantages and disadvantages from a pedagogical, cost and management perspective. It also discusses the lessons learned and difficulties found in the deployment of the different network laboratory configurations We hope our methodology and experience in designing and improving the implementation of remotely accessible computer networking laboratory facilities can help other instructors and institutions in their own efforts to offer effective and manageable laboratory experiences to distance education students. COMPUTER NETWORK LABORATORY DESIGN Computer network laboratories can be implemented in many ways. They can rely on a simulation environment, or on virtualized or physical infrastructures [1, 6-11]. Simulationbased laboratories rely on software that simulates the behaviors of network elements. This approach is typically used when the experiments to be performed are too expensive or difficult to be undertaken with real equipment or when remote access to real physical devices is too costly or inconvenient. The size of the simulated network depends on the computational power and time allocated to its analysis. A problem with this type of design is that the results of the simulation are only as good as the code written into the software and therefore there is a risk of not getting realistic or accurate results from the simulations. Virtualized infrastructures make use of the instantiation of several virtual machine (VM) configurations inside each one of the (physical) server systems of a laboratory. Each of the VMs can be configured to act as a server, client or routing device within a network formed by grouping and interconnecting different VMs. The use of VMs also enables a laboratory administrator to easily restore the laboratory s configuration to a default state by reloading the necessary VMs when required [3]. Laboratories based on a physical infrastructure configuration primarily make use of real physical networking devices for the setup of experiments. The devices can be deployed in either a centralized or distributed topology [1]. These laboratories provide many advantages including access to real network interfaces and results and interactions that mimic those found in real world environments. However, laboratories following this approach are more expensive to implement and can become difficult to manage if not planned correctly. In general, laboratory based distance education is difficult to offer since the laboratory s devices must be made accessible to distance students in such a way that they are able to have a learning experience that is equal or very F3C-1

2 comparable to the one obtained by in-situ (campus-based) students. The satisfaction of this requirement relies on providing adequate remote access to the laboratory and on having a laboratory setup that offers enough connectivity and management flexibility to deliver similar learning experiences to distance and in-situ students. REMOTE ACCESS & LABORATORY CONFIGURATIONS In order to evaluate the benefits and drawbacks of different laboratory configurations for distance education, the following setups were deployed for and tested by distance education students of an intermediate level computer networking course taught by the author: i. Remote access to the devices of SU s networking laboratory facility. This facility previously used for campus-only computer networking courses was upgraded to support remote access and monitoring. ii. Remote access to a Cisco based NETLAB system. This system although well organized is vendor-specific and deploying non-cisco defined configurations proved challenging. iii. Software based simulation of computer networking devices through the use of Cisco s Packet Tracer software. The machines which had the software were accessed remotely by students. Each of these configurations is described in the following sub-sections. I. Remote access to a physical lab infrastructure When working with physical devices in a campus-based computer networking laboratory, students get to manipulate the connectivity between different network ports and the configuration of the various networking devices in the laboratory (routers and switches) via their management interfaces. In a remote access configuration, these same capabilities should be provided to students. Figure 1 illustrates the remote access setup employed at SU to give access to distance students to a physical lab infrastructure. Devices in the laboratory are grouped in department units and typically, a team of two students gets assigned a specific department. Each department consists of one router, a switch, a patch panel and two servers. The servers have enough capacity to host several virtual machines which can act as the nodes of a network. All ports of the devices in a department can be interconnected via a patch panel and all departments can be interconnected through additional patch panels set for that purpose. The current laboratory infrastructure has 14 departments in total providing remote access capabilities for several students at the same time. To provide flexible and remote access to the management interfaces of the laboratory s devices so that students can configure them from a command line level, we use a Serial Link Concentrator (SLC). The SLC is a commercial device that handles many serial interfaces to which all the RS-232 management ports of the network devices are connected. Through the SLC any device in the laboratory can be configured without having the student move extra cables and/or configuring a management connection to a device through other means (i.e. fixing a data port and allocating an IP address to it). To efficiently configure and manage the virtual machines (VMs) in each of the servers of a department, the servers have been pre-configured with a hypervisor (VMware ESX). Additionally, a VMware vsphere server allows centralized management and monitoring of all virtual machines deployed in the servers of the laboratory. FIGURE 1. REMOTE ACCESS TO A PHYSICAL LAB INFRASTRUCTURE F3C-2

3 Distance education students using the laboratory log into the VMware vsphere server which offers enough capabilities to the students to activate, shutdown or restart any VM or group of VMs depending on the requirements of a lab exercise. For ease of use and manageability most students after activating their VMs log into the SLC through a secure shell terminal session from a VM and manage their department s devices through that session. A current drawback of the setup is that the student s flexibility to enable connections across several device ports is limited. Laboratory assignments are scheduled to be completed during a two-week interval and the lab administrators have to pre-configure the correct sets of patch-panel connections in each department s patch panel so that distance education students can perform their lab assignments. Currently, students can only control connectivity on a port by enabling or disabling the selected port. Ongoing enhancements to the laboratory will increase the capabilities for remote inter-connection management across device ports reducing the burden on administrators. II. Remote access to a NETLAB infrastructure NETLAB is a line of products of NDG - Network Development Group for distance based or blended (distance and in-site) education on computer networking [4]. Depending on its configuration, a NETLAB system setup will contain several routers and switch devices along with servers to host virtual machines. The devices are grouped in equipment pods depending on the requirements of a particular lab exercise. Figure 2 shows the remotely accessible NETLAB system setup used in our lab. As a commercially developed product NETLAB offers the software and hardware interfaces to provide remote access to the equipment pods, schedule their use by students and manage/restore the configuration of devices. These capabilities reduce most of the management burden on laboratory administrators except for the tasks involved in setting up a pod configuration to match a specific assignment requirement. However, the integrated scheduling and remote access capabilities of the system make it a very attractive system to offer learning experiences on computer networking to distance education students. III. Remote access to a network simulation infrastructure Simulation based networking laboratories are a great option for institutions that have limited funds, and insufficient infrastructure to support physical hardware. Remote desktop access can be used to provide the students access to the computer systems in the laboratory facility that contain the simulation software [5, 6]. In our setup, we used Cisco s Packet Tracer application which can provide very realistic device emulation features although it is vendorcentric and has restrictions related to licensing and emulation of advanced device features. Figure 3 shows the configuration we used to enable remote access to a simulation-based network laboratory. A pool of servers was setup and managed via VMware vsphere so that when students logged in to the lab, they could create a windows XP virtual machine (VM) on any available server. The VM had the Packet Tracer software installed in it and students could make use of it via a remote desktop session. FIGURE 3. REMOTE ACCESS TO A NETWORK SIMULATION INFRASTRUCTURE FIGURE 2. REMOTE ACCESS TO A NETLAB INFRASTRUCTURE COMPARISON AND ANALYSIS OF CONFIGURATIONS Each of the networking lab configurations mentioned previously will be compared and analyzed based on the following criteria: infrastructure cost, flexibility, complexity, pedagogy, and student likeability. Infrastructure cost: From the three remote laboratory configurations studied, the one with the highest implementation cost was the laboratory supported on physical devices. Equipment, space and energy costs must F3C-3

4 be considered for this setup along with the costs of management, devices and software. Management costs are usually lower in the case of a NETLAB setup but the costs of the equipment rack and of the devices for each pod have to be considered. The simulation based setup has the lowest cost of all as long as the per-license cost of software is low. For all configurations the cost of the communication equipment and links to provide remote access is almost the same but due to the heavy reliance on remote desktop sessions for all configurations, the capacity of the links to the laboratory have to be dimensioned properly based on the number of students that will simultaneously access the laboratory. Students accessing the laboratory also incur a cost in the sense that they must have a capable computing system and a data connection that can adequately support the remote interactions with the laboratory (remote desktop sessions). In terms of data connection speed, students with data connections with speeds higher than 256 Kbps (downlink) reported good average response times. Flexibility: The degree of flexibility to configure experiments varies across the different setups tested. The physical lab infrastructure offers the highest degree of flexibility but it is limited by the number of devices available in the laboratory and management tools available to laboratory administrators for configuring experiments. The NETLAB setup is easier to manage but limits the configuration of experiments to those that closely follow pre-determined configurations. Although a more diverse set of experiments can be provided by lab administrators via the development of fully customized pods, their development proved to be complex but it could be improved with additional training on the product. For the case of simulation based environments, the range of laboratory experiments that can be setup is limited by the capabilities of the software and the computer system over which it executes. Complexity: The complexity to setup laboratory experiments for students in the physical lab infrastructure is higher than that required in the other setups. Most of the complexity is determined by the device and connection management capabilities of the laboratory. The NETLAB setup offers tools to easily configure experiments (under the flexibility restrictions mentioned previously). Configuring new experiments in the simulation based setup only required defining new elements for each experiment via a GUI. Pedagogy: Teaching activities for each lab setup should focus on the strengths offered by each configuration. Simulation-based environments are good for introducing students to new concepts and to analyze large network scenarios that would be cost-prohibitive to implement with real equipment in an academic institution. Physical and Netlab based laboratories provide a more realistic experience than simulation-based experiments and allow students to interact with the advanced features of network devices that are not available in simulation software. These laboratories also allow for the analysis of real traffic flows (packet captures) that provide students with detailed understanding of protocol behavior. The flexibility and complexity characteristics of each laboratory setup affect some of its pedagogical aspects and the way students interact with it. For example, if a student makes a mistake while performing a lab exercise in a physical lab setup, it can be difficult and time consuming for him/her to return a device to a previous or neutral state unless the student has taken precautions to do so. In contrast, simulation environments usually provide an easy to use interface to instantiate a new device quickly without waiting for it to reboot or stabilize. Netlab devices can be restarted just like in a physical lab setup but the system keeps track of the history of commands issued by a student which makes it easy for him/her to determine when and how a mistake was made and/or discuss his procedures with an instructor who can then provide more accurate feedback. Likeability by students: A total of 22 distance education students made use of the three laboratory configurations described previously during the Fall 2010 semester of an intermediate level computer networking and telecommunications course. Students of the course had the typical computer networking knowledge of a senior undergraduate or graduate student in ICT fields, such as CS, IS, Telecom and EE. The feedback from students provided guidelines for improving the remote access capabilities of SU s networking laboratory facility as well as a sense of the likes and dislikes of students regarding remote hands-on work with networking devices and software. From a survey answered by 16 of the students of the course the preferred remote laboratory setup was the one based on simulation software (7 students - 44% of respondents), followed by the NETLAB based setup (5 students - 31% of respondents). Third place was for the setup providing remote access to a physical lab infrastructure (3 students - 19% of respondents). One student expressed no preference for any of the setups. The students preference for the simulation based setup was influenced by the fact that with this setup they had less difficulties in completing laboratory assignments. Time restrictions for the assignments were not as severe as in the other setups since scheduling the use of equipment was not required in this configuration. The low likeability for the physical laboratory setup was determined by the perceived higher complexity of the lab exercises assigned to be performed and the intermittent configuration management problems that affected the execution of some of the experiments by the students. However, the experiences with remote access to devices in a physical lab and to a NETLAB setup were appreciated by at least 50% of the students to be more realistic and engaging. The students likeability scores are the opposite of what the author/instructor would have preferred. However, they seem to indicate that a strategy where introductory F3C-4

5 TABLE 1. COMPARISON OF DIFFERENT LABORATORY SETUPS laboratory assignments are performed with simulation software and more advanced assignments are performed with remote access to setups that make use of real equipment, might provide the best combination of learning experiences for students. Future work will validate this hypothesis. A summary of the comparison results for the different laboratory setups is presented in Table 1. additional time on assignments, adding to the frustration. Additionally, laboratory support staff must know about the experiments being conducted remotely which, depending on the staff available either limits the number of experiments that can be adequately supported in the lab (from a human resource perspective) or imposes additional costs on its operation due to the extra staff required to operate it. A remotely accessible laboratory makes learning interactions easier on students who cannot install software in their computer environments due to security policies in their place of work or limitations on their own computing devices. Redundancy on the data connections that provide remote access to the laboratory and on the connections that provide accessibility to its management or configuration platform should be in place in order to handle failures on the primary connections to these systems. The most important advantage to using laboratories based on physical infrastructure is that they provide a learning experience that is more realistic to the environment students will be working on when they leave school. However, it is the task of the instructor to design laboratory assignments that will promote critical thinking and stimulate problem solving skills instead of using a fully guided step-by-step approach which deviates from reality. ACKNOWLEDGMENTS LESSONS LEARNED AND CONCLUSIONS Providing remote access to a computer networking laboratory infrastructure extends the learning experiences of the laboratory to distance students. This capability allows an institution to deliver instruction and knowledge on important technologies to distance students. However, the implementation of a computer networking laboratory for distance education requires determining the balance between academic objectives, budget and maintenance constraints that best satisfies an institution. The following paragraphs describe a set of lessons learned and conclusions derived from the implementation of the laboratory setups described in this paper and the interactions that distance students had with them. Distance learning students are typically persons seeking to improve their educational background and maybe holding a job and family responsibilities. The times at which these students decide to engage on academic assignments are usually taken from their traditional free time at work or home or even their sleep/rest hours. Thus, students access a remote laboratory at very unusual times during the day and expect to find 24/7 support from laboratory staff. If the organization in charge of the laboratory has not planned for that level of support, students will get frustrated and/or spend The author would like to thank the Deans of the School of Information Studies at Syracuse University for the approval of the internal development grant for the Networking Lab Virtualization Project from which the results of this work were derived. Additional thanks to the staff of the SU s ITELL lab and professor Bahram Attaie for their help and support in the configuration of the different laboratory setups. REFERENCES [1] Caicedo, C. E. and Cerroni, W., "Design of a Computer Networking Laboratory for Efficient Manageability and Effective Teaching," in ASEE/IEEE Frontiers in Education Conference San Antonio, TX, [2] Comer, D. E., Hands-on Networking with Internet Technologies, 2nd edition, Prentice Hall, [3] Gerdes, J. and Tilley, S. "A conceptual overview of the virtual networking laboratory," in 8th ACM SIGITE conference on Information technology education, 2007, pp [4] Network Development Group, NETLAB Product Line, [5] Sicker, D. C., et al. "Assessing the Effectiveness of Remote Networking Laboratories." In ASEE/IEEE Frontiers in Education Conference, Indianapois, IN, F3C-5

6 [6] Disston, S. and Caicedo, C. Approaches to the Design of Computer Networking Laboratories, ITERA 2010 conference, Nashville, TN, 2010 [7] S. Abbott-McCune, A. J. Newtson, J. Girard, and B. S. Goda, "Developing a reconfigurable network lab," in 9th ACM SIGITE conference on Information technology education, 2008, pp [8] E. Freudenthal, "A Virtualized Network Teaching Laboratory." Proc. ASEE (American Society for Engineering Education) Annual Conference and Exposition, June [9] A. Gaspar, S. Langevin, and W. D. Armitage, "Virtualization Technologies in the Undergraduate IT Curriculum", IT PROFESSIONAL, vol. 9, p. 10, [10] E. A. Lawson and W. Stackpole, "Does a virtual networking laboratory result in similar student achievement and satisfaction?," in 7th conference on Information technology education: ACM, [11] Melkonyan, Arsen and David Akopian: C.L. Philip Chen. "Work in Progress- Real- Time Remote Internet-Based Communication Laboratory." In ASEE/IEEE Frontiers in Education Conference. San Antonio, TX AUTHOR INFORMATION Carlos E. Caicedo Bastidas, Assistant Professor & Director of the Center for Convergence and Emerging Network Technologies (CCENT), School of Information Studies, Syracuse University, ccaicedo@syr.edu. F3C-6