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EVALUATING DEPLOYMENT OF CENTRALIZED COURSE SERVER AND MOBILE WEB CLIENTS

We are studying the effects of deploying a proposed centralized course server in the SUNY Fredonia campus network and introducing mobile web clients using OPNET. We have simulated web clients accessing the server that resides on a Gigabit link in the central network facilities. We also simulate the mobile web clients in classrooms and evaluate their performance. Initial results have indicated negligible packet loss and annoying additional delays but with server connected directly to the central switch, the increase in the delays is not noticeable. In case of mobile nodes, we are working on the generalized problems of determining the performance with web applications and error rates for various WLAN parameters. Introduction OPNET has been used to study and provide assistance in campus network modifications in SUNY Fredonia. SUNY Fredonia is a campus of SUNY with about 5000 students. Most resident students use the network frequently and overall usage is between moderate to heavy. Last year the OPNET simulation results exposed a potential congestion point in the campus network where 13 residence halls collapsed into a single Cisco 5500 [1]. The network manager corrected the problem before it could jeopardize the performance. The campus network has been changed recently from the description given in [1]. Residence Hall core switch is upgraded from a WS-C5500 to a WS-C6509. With the Campus Core switch/router and the ResNet core equipment side by side, we are able to implement all sub-networks on both switches. Thus each router routes its primary subnets and is also acting as secondary for the other's routed subnets via HSRP (Cisco's Hot Standby Routing Protocol). In the event that either router fails, the other picks up automatically. Many of the 100Mbps switches and fiber links to main buildings have been upgraded to Gigabit Ethernet. Besides improving the internal structure, campus has expanded the Internet bandwidth from a single T1 to 8 x T1 (12 Mbps) via three Cisco 3640 routers. A Cisco CE560 content switch was added recently. The content engine caches previously fetched web pages for all three routers. Since turning it on, it has been delivering about 40% of the web content on campus. When a user goes outside of fredonia.edu for a web page, the routers send a query to the content engine, if the page is cached it sends a "light query" to check the page version with the server. If the content engine has the most recent update, it sends the page to the requester at wire speed. If not, the router passes the query out onto the Internet. Also, a campus wide firewall is in early deployment stage. The AIT (Academic Information Technology) has recently proposed that all of the current campus web pages related to courses be moved to a single powerful Win-NT/2000 server. Presently, professors who maintain web pages have stored them mostly on their individual departmental servers. We have initiated a study based on OPNET simulation to evaluate the performance pros and cons of this proposed change. Mobile computing will be an integral part of the targeted ubiquitous computing environment. Third generation wireless systems and the Internet are pushing the mobile telecommunications market [2]. Mobile users tend to move around and still maintain active communication links. There is a growing need to provide quality of service to the mobile users based on an increase in the number of time-sensitive applications. Significant amount of work has been done to deal with the issue of providing multimedia services in the mobile wireless network [3,4,5]. Our study takes into account the future Fredonia campus network scenario when mobile computers would be taken into the traditional classrooms and professors would be able to download and show multimedia presentations to their students. For this purpose, we have added an access point in one of the academic buildings and provided ten mobile clients. These mobile clients will also be feeding from the same central course server. We also look at the performance of mobile nodes while adjusting various WLAN parameters. Rest of the paper is divided into two sections. In the next section, we introduce the experimental setup and simulation results for the campus course server proposal. Later, we present results of simulation with the mobile clients in an academic building as well as an independent wireless LAN that connects to the fixed network. Simulations With Centralized Course Server The current layout of the campus network is such that all local web-related material for a department is based in that department's subnet and such traffic does not need to transmit at a higher level. The proposed plan by AIT would place a powerful Windows NT/2000 server in the central network facilities and all web queries and responses would be carried by the central network switches. The most obvious issue with such a change is the increase in traffic through the central