Hybrid Fiber/Copper LAN Meets School's 25-Year Networking Requirements
by SAM PETRUSO, Coordinator, Computer Services and VINCE HUMES, Systems Manager Millcreek Township School District Erie, Pa. Millcreek Township School District is in the process of implementing an innovative new curriculum, one combining traditional academic studies with early exposure to real-world business practices. The program, known as the "Community and World at Work," has been adopted Walnut Creek Middle School (grades 6 through 8). In support of the new curriculum, and with an eye to the future, the district decided to install an advanced networked computer environment. The goal was to build a computing environment that would provide the capacity needed to last 25 years, while keeping pace with emerging technologies such as multimedia. To meet this goal, the district's technology staff knew that they would have to create an extendable cable plant and network infrastructure. Ultimately, they opted for a plant architecture based on mix of copper and fiber-optic technologies. This article discusses the innovative curriculum and also delves deeply into the technical side of the new network. Final decisions, and how they were arrived at, are described in detail. Physical & Philosophical The Walnut Creek Middle School is unique in that it is organized like many businesses, both in terms of physical layout and goals. Physically, the classrooms for each grade are clustered together around a common "company" area (Photo 1) -- not along hallways as in a conventional school. Philosophically, the theme of Community and World of Work is a good match to the curriculum of the middle grades as well as to the intellectual, emotional and physical-activity needs of its students. The concepts of "companies" and "production areas" are integrated into multidisciplinary learning activities; the physical facilities have been expressly designed to support the curriculum. The new curriculum consists of traditional core subjects such as math, English and science, which are then bolstered by other studies related to actual business practices. Every school year, each of the "companies" (grades) works on a new product line. Students are immersed in all aspects of product development and marketing, from concept and design, to manufacturing and sales. Physically, "production areas" -- containing specialized computer systems (Macs with add-in cards), peripherals and assorted external devices -- enable the collaborative, hands-on learning. This new curriculum has the full support of the local business community. In fact, one local firm helped the school work within ISO-9000's quality guidelines in the areas of design and manufacturing. The following scenario offers a glimpse of the new curriculum in action: A student "company" planning team prepares to implement a project. These seventh graders are working in a cross-disciplinary mode that combines science, social studies, math and language arts. The team has a limited amount of time to find and gather pertinent materials and to then develop a "product" that can be shared in the class and put into "production mode." This (and every) team starts by vicariously experiencing the real life behind product development. They gather material from the multimedia, statistical and print sources offered over the network; they use e-mail and fax to correspond with industry experts and students at other schools. Once the "product" is agreed upon and put into "production," students utilize many specialized pieces of equipment. Depending on the project, some student teams may write reports based on their experiences and observations; others write stories, make videos or create a drama about what they have learned. All is done, however, within the larger context of a "company" producing something tangible, as in real business. Teacher teams serve as advisors to various student groups, depending on needs and interests. Instructor teams meet once a week to plan activities for each project, check on the resources and to ensure that students cover the necessary content for the district's curriculum plan while they also are given the opportunity to study something in sufficient depth to "know" it. Instructor teams also develop an assessment plan for the outcomes of each student group. Content, mastery of new skills, communications, work style, level of effort and peer assessment all play a role in the evaluation. Following each project, the teacher team meets with students to discuss performance and make individual plans for what a student should stress during the next project. Lofty Networking Goals In considering an overall computer environment (to support their new curriculum and more), the school district had three primary goals: First, provide computing facilities that enhance each student's educational experience. Second, enhance teacher productivity and facilitate development of a more robust curriculum. Third, improve administrative efficiency by simplifying communications and record keeping. Prior to designing the computer installation for the middle school, the Millcreek School District already had substantial experience with computers. Schools throughout the district were equipped with Apple Macintosh computers, and a VAX minicomputer was in use in the central administration building to provide a single database for records. The new network, however, comes from a greater vision. It is an integral part of the districtwide plan for local area networks and wide area networks (LANs and WANs, respectively). This is necessary to connect 12 schools and an education center together in a network spanning 29.5 square miles. The buildings need this infrastructure to ensure that whatever data is transmitted or received has the same integrity, regardless of any new applications using new technologies. The fiber/Category 5 UTP (unshielded twisted pair) copper network that was chosen supports that kind of standardization. The district's goal was to install about 300 Macintoshes in the new school. Most classrooms would be equipped with a cluster of computers in a 3:1 student-to-computer ratio. Some rooms, such as the language arts rooms, would be saturated with as many as 30 computers, with one computer for each student (Photo 2). The district also wanted to boost connectivity in the new computer system, not only between computers within the school, but between the school and the administrative central office. In previous installations, the district used an AppleTalk LAN with some success to connect small numbers of computer systems within each classroom and to share peripherals such as printers. However, AppleTalk's low bandwidth had already proven to be inadequate for performing tasks such as loading large files and running programs from a remote file server. In the new school, the district wanted to deploy a network with sufficient bandwidth to link all of the school's computers with multiple servers to provide shared program and data storage. The network also had to supply a flexible means of sharing peripheral devices, both within classrooms and among computers in different classrooms. Juggling Short- and Long-Term Connectivity Requirements Most challenging of all, the environment had to provide an affordable solution that encompassed both today's technologies as well as those envisioned for tomorrow. Short-term goals were relatively simple. The installation would have to allow the sharing of data files, programs and peripherals, via file servers, while providing access speeds reasonably close to those provided by data-access devices. The installation would also have to be linked to the district's central administration office. Both of these requirements, the engineers recognized, could be easily satisfied with an Ethernet LAN and a T1 connection. A longer term solution, however, required greater innovation, particularly with the advent of interactive educational technologies such as collaborative learning (at a distance), interactive video and videoconferencing. Today such technologies, which require the real-time transmission of enormous audio and video data streams, are usually handled via cable-TV-type technology using dedicated coaxial links. Integrating these technologies into the computer network requires a LAN with a much higher bandwidth than that currently provided by Ethernet. With an eye to the future, the engineers decided that the cable plant and network infrastructure needed to be easily upgradeable to support at least 100Mbits per second (Mbps) data rates. Cost was a key constraint, but it was recognized that the cost of installing a new network far exceeds the cost of the cable itself. Consequently, it was decided that the incremental cost associated with installing a more capable cable plant and infrastructure now would be more than offset by the savings associated with not having to install a new network for 25 years. Fiber vs. Copper The long-term requirement for a 100Mbps data rate capability led the district's engineers to consider fiber-optic cable for the school's local area network. Because of its high bandwidth, fiber can comfortably handle the data rates used with LANs like FDDI (Fiber Distributed Data Interface). It also provides the headroom needed to upgrade to higher-speed networks such as Fibre Channel and ATM (Asynchronous Transfer Mode). Still, the cost premium associated with an all-fiber network (relative to copper) was a concern. The total cost includes not just fiber for the cable, but also related fiber-optic components such as connectors, patch panels, transceivers and network adapter cards. Though the cost difference between fiber- and copper-based LANs continues to shrink, given the constraints of the Millcreek budget, the difference was still significant enough to make the engineers shy away from an all-fiber solution. An all-copper approach was also considered by the engineers. Though copper cable can't match fiber's top-end bandwidth, 100Mbps LANs such as FDDI have already been adapted to copper (via use of Copper Distributed Data Interface, known as CDDI), and copper-based 100Mbps extensions of Ethernet are under consideration. Still, even with copper, the cost associated with equipping the entire network for 100Mbps transmission exceeded the district's budget. The primary stumbling block was the cost of the network adapter cards, one of which would be required for each Mac on the network. A Hybrid Solution In the end, the engineers opted for a 100Mbps cable plant using AT&T's SYSTIMAX Structured Cabling System (SCS). It combines a fiber optic backbone with copper connections to the desktop. Initially, to save cost, both the copper and fiber portions of the network have been equipped to run Ethernet at 10Mbps. Later, as bandwidth requirements increase, both the fiber backbone and copper workgroup (desktop) connections can be upgraded for 100Mbps transmission without altering the cable plant. The school's 300 Macs are linked via seven Chipcom hubs (one for each of the six "company" areas and one for the school administration area), which are located in wiring closets spread through the building.
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(Photo 3 shows a Wire Closet for a "company" area: six classrooms and a "production" area.) Category 5 UTP copper wiring is used to connect each computer with its respective hubs. The Macs and hubs are equipped with relatively inexpensive copper-based 10BaseT LAN cards that provide the network interface. Runs of 10BaseT cable, which are terminated in RJ-11-type phone jacks, are provided in all of the expected places, including classrooms, the media center (library) and administrative offices. Anticipating emerging technologies, such as interactive multimedia, 10BaseT cable runs have also been provided in a number of non-traditional areas. Wiring the lobby, for example, will enable the school to make use of information kiosks. Similarly, 10BaseT connections along the raised stages in the gymnasium and other large-group instruction areas will enable the school to handle computer-based presentations. Each of the seven Chipcom hubs is tied to a central hub via a fiber-optic interface. The point-to-point fiber connections run the same Ethernet protocol as the local workgroup UTP LANs. The central hub also includes a router that provides a 1.5Mbps T1 interface between the school's computer system and the remote VAX located in the district's central administration building. The system's file servers are located in the central wiring closet (Photo 4). They are connected to the hubs via 10BaseT LAN adapters in the same way that the workstations are connected. Initially, the engineers have installed four servers, which should prove adequate to handle the school's near term data storage needs. Later, as both storage and bandwidth requirements increase, file servers can be added to any of the hubs. Each server's data and program storage areas may be designated as accessible to all Macintosh computers, dedicated to a single Mac or limited to subgroups of users such as a specific "company" or grade. Computer peripherals, like printers, can be shared among the system's Macs in one of two ways. For sharing within a classroom, peripherals may be linked via an AppleTalk LAN. Global sharing (among computers located in remote classrooms) is achieved by locating the peripherals in wiring closets and connecting them directly to the hubs. Future Expansion The Millcreek network architecture has been designed from the ground up with expansion in mind. As bandwidth requirements increase, and the cost of 100Mbps network components decrease, the school's engineers will be able to incrementally upgrade the system. The design of the Chipcom hub, in particular, makes incremental upgrades a breeze. Initially, for example, the school may want to upgrade the fiber backbone to support 100Mbps transmission rates, while maintaining 10Mbps hub-to-desktop connections. This can be easily done by replacing the fiber-based Ethernet interface cards used in the hub with FDDI cards. Later, when higher bandwidth to the desktop is required, the hub-to-desktop Ethernet cards can be replaced with 100Mbps CDDI cards, and the Ethernet adapter cards used in each Macintosh can be replaced with CDDI adapter cards. The central hub can also be upgraded easily to support new WAN connections to the central office or elsewhere. After deciding on a wiring topology for the cable plant, the district's engineers were faced with the task of finding a contractor for the installation. Ultimately, they published a specification (for bids) that required the contractor to have experience installing six or more similar networks. It also required the contractor to warranty the cable plant -- not just for immediate 10Mbps needs, but for the 100Mbps speeds that would be required in the future. The contract was awarded to Data Processing Sciences, of Pittsburgh, Pa. The cable plant and network installation was completed in August 1993 and has been operating reliably ever since. Data Processing Sciences installed and configured all the hubs, routers, gateways and T1 equipment with AT&T as the subcontractor for the cable plant architecture. Environment Bears Fruit Even now, students and teachers at the Walnut Creek Middle School are reaping the benefits of the new computer system. For members of the faculty, each of whom has his or her own computer, the system has enhanced communications. Its e-mail, in particular, has made it easier for teachers to keep in touch, not only within Walnut Creek Middle School, but throughout the district. Still, the principal beneficiaries of the new system have been the students. Through the computer network, they now have easy access to a wealth of shared resources, including a library of CD-ROMs that can be accessed from anywhere in the school. The network also gives the students access to industry experts. Through the Internet, for example, students can communicate with business experts, college professors and other students worldwide. The new computing environment also fosters a collaborative, interactive approach to learning. In the language arts lab, for example, teachers can use their Macs and an LCD panel to project an assignment onto an overhead screen. Students and teachers may then collaboratively critique and edit it. By placing interactive learning resources at each student's fingertips, the new system empowers students to work out problems on their own. In effect, the student becomes the teacher, while the teachers can consult, observe and guide student activities. The use of computers also provides an important side benefit: As students become proficient with their computers, they are able to apply that knowledge across multiple subject areas. For example, some students have already used a HyperCard software stack to set up a plant and animal classification system. In the long term, the goal of Walnut Creek's principal, Dr. Ken Borland, is to bring true interactive learning to the school through use of interactive video systems. Currently, they utilize an advanced audio-video system to display educational events such as space shuttle flights. However, this is standard TV technology and not interactive. Eventually, as video-telephony equipment becomes more affordable, Dr. Borland would like to integrate video directly into the computing environment. And when that time comes, the infrastructure will be there, waiting. For more information, call Millcreek Township School District at (814) 835-5315 or send e-mail to their AppleLink address: K1535. Sam Petruso has taught both social studies and geography in the Millcreek Schools, as well as being an Audio Visual Specialist for 18 years. During that time, Petruso has served as Coordinator of Computer Services for the district. Vince Humes has worked in the computer and communications fields for the past 14 years, and been employed in manufacturing, consulting and education. The last seven years, he has served as the Systems Manager for Millcreek Schools. Products or companies mentioned: AT&T SYSTIMAX Structured Cabling System (SCS); AT&T Network Cable Systems, Morristown, N.J. Chipcom Corp., Southborough, Mass. Data Processing Sciences, Pittsburgh, Pa.
This article originally appeared in the 05/01/1994 issue of THE Journal.