Modular network delivers data, video and voice to the desktop

Modular network delivers data, video and voice to the desktop

Complementing the migration to asynchronous transfer mode technology, a modular fiber-optic/copper building-wide network brings megabit-bandwidth to computer users

Barbara MaAskant

rollins school of public health

emory university

Because the new Rollins School of Public Health occupied office space in a building across the street from the main campus in Atlanta, Emory University decided to construct a new building with an advanced fiber-optic/ copper/asynchronous transfer mode communications network that would carry multimedia signal transmissions to the desktop.

In researching premises building networks, university officials discovered a paper authored by John Reeves, regional manager at AT&T Distribution Technologies in Atlanta, which described that company`s Systimax structured cabling system. Unfortunately, building construction was already underway, and many capabilities of the modular cabling system could not be implemented. However, the university did have time to redesign the deployment of the computing department`s resources and to integrate several facets of the AT&T system into the new building.

The modular structured cabling system installed in the new building enables the use of the existing network and computer hardware, thereby saving equipment costs. Each floor of the 10-story building contains classrooms, laboratories, conference rooms, offices, support facilities and its own Ethernet local area network.

The school`s data networking needs in the old building were supported by a LAN and a suite of VMS and Unix file servers. The network backbone consisted of Ethernet hardware running transmission control protocol/Internet protocol under Pathworks for DOS-based personal computers, TCP/IP for Unix machines and Appleshare for Macintosh computers. The data network was connected to Emory`s campus-wide backbone via a router and provided access to other LANs within the university community and to wide area network services such as Internet and World Wide Web.

In the old building, network moves, adds and changes were minor inconveniences. In the new location, however, network modifications could result in major expenses--possibly $150 to $400 each. On this scale, an entire year`s operating funds of the school`s limited budget would be quickly consumed.

Consequently, to minimize costs, each office, laboratory and classroom contains at least one LAN connection. In fact, for network flexibility, three connection outlets are installed in each classroom--one for the instructor, one for mobile demonstration equipment and one in the ceiling for wireless LAN interfaces. These interfaces provide communications links via radio frequency or infrared signals between the school`s LAN and the students` personal communicators or computers. The two computer laboratories contain more than 25 of the 524 permanent connections installed in the new building.

In 1992, when the school`s LAN was originally planned, implementing fiber-optic cable to the desktop was considered too expensive. Because administrators now believe that fiber is the transmission medium choice of the future, the school installed fiber-optic cables to each connection.

User needs

Emory University uses a 100-megabit-per-second fiber distributed data interface backbone network to interconnect several LANs scattered across its campus. An FDDI backbone is also used in the new building to simplify the connection to other LANs on the campus and as a gateway to the Internet.

Although strained to capacity, the 10-Mbit/sec Ethernet backbone in the old building provided adequate communications. But with an independent Ethernet LAN connected to each floor in the new building and the potential for hundreds of simultaneous users, the new backbone needed considerably more bandwidth to support an advanced premises building network.

Choosing a high-performance backbone technology is difficult enough in an environment where most users require the same kind of service. At the School of Public Health, some users need to process large amounts of data in bursts and others only need to move data between network nodes. This situation is further complicated by the anticipated need to handle multimedia information in real time.

School officials carefully studied present and anticipated information and local area networking needs because many number-crunching and modeling applications exist within the sphere of public health functions. The Division of Epidemiology, for ex ample, conducts re search projects on large populations to trace the etiology of diseases, thereby requiring the analysis of enormous amounts of data. The Division of Biostatistics, on the other hand, performs more modeling applications; in one study, it is calculating how long it would take to eradicate a disease with a given immunization program.

Although each user group has different needs, the common denominator -- sig nificant bandwidth requirements--convinced school officials to move to ATM technology. Through switched interconnections, ATM provides full network bandwidth to each user, regardless of the number of other active users. In addition, ATM`s bandwidth, currently running to 155 Mbits/sec, will soon be extended to 622 Mbits/sec and to 2.5 gigabits per second in the future, as proposed by the ATM Forum.

School officials, therefore, decided to abandon FDDI in favor of an ATM switch for the new backbone network. Unlike FDDI and other token ring LANs, in which signals travel from node to node until they reach their destination, signals on an ATM backbone travel between each node and the switch using virtual connections.

To complement the school`s migration to ATM technology and to deliver text, graphics, video, voice and database server access directly to the desktop, a structured premises cabling system has been installed.

Because most of the PCs contain Ethernet cards that interface the network nodes to twisted-pair copper wires, Category 5 data-grade copper cables have been installed in the new network for data communications applications. In anticipation of eventually adding voice and video network services, a second copper cable is supplied to support these services.

In addition, one fiber-pair termination is available at each desktop to enable users to take advantage of communications speeds higher than 100 megabits per second, regardless of the communications interface.

Because the new building is a multistory tower, vertical and horizontal connections are provided in a voice/ data closet on each floor, and closets are aligned vertically with closets on adjacent floors. Each closet contains a hub from which cabling is run through overhead cable channels to each outlet connection on that floor. A typical wall outlet has two data, one voice and two multimode fiber connections.

Cables running vertically from the voice/data closets connect the hub on each floor to the ATM switch. Communications on each floor flow horizontally from the originating node to a hub and then vertically to the ATM switch. From the switch, communications pass to the network operations center hub and, via this hub, move to servers, an extended LAN connection or to the router and the university`s main campus backbone. The local hubs also provide the required signal and protocol translations between the copper-based Ethernet LANs and the fiber-optic ATM backbone.

Each of the 524 permanent connections consists of two Category 5 data and one Category 3 voice twisted-pair cables, as well as two multimode optical fibers. More than 36 miles of Category 5 twisted-pair cable and almost 18 miles of horizontal two-fiber multimode cable are installed between these connections and their corresponding concentrator. Dual vertical runs between the concentrators and the ATM switch require 2230 feet of six-fiber multimode riser cable. The system also contains 1060 information ports, fourteen 66-port and four 48-port patch panels, and 4136 connectors and couplers. Terminations are made to flush, wall-mounted multimedia outlets designed by AT&T for the school.

On each floor, a multimedia access center hub supports 183 user connections. All the hubs are equipped with a six-port bridge/router management module and the proper number of Ethernet repeater modules to support the user base of that hub. There are 21 to 63 Ethernet ports in each hub. The local Ethernet LANs are connected to the ATM backbone by a 155-Mbit/sec ATM bridge/router management module.

The ATM switch connects to centralized servers and communications hardware via a 155-Mbit/sec switching hub. This hub also contains two FDDI multimode interface processors: One provides communications between the backbone and the school`s existing suite of Unix file servers, and the other furnishes an interface for the ATM backbone to a router and Emory`s campus-wide FDDI backbone.

Growth plans

Although the new building houses most of the School of Public Health facilities, the school`s continued growth will require offices in other buildings, both on and off the Emory campus. Communications between these satellite offices and the new building will be provided by an Ethernet link. To accommodate this link, an Ethernet interface processor has been added to provide users in those buildings with direct access to the ATM backbone.

During the past few years, the School of Public Health and the Center for Disease Control located adjacent to the Emory campus have developed a working relationship. Because the center offers access to its computerized databases, the school has established an Ethernet link between the center and the new building to provide researchers with a communications gateway.

The LANs on each floor of the new building are copper-based 10-Mbit/sec Ethernet networks, which provide limited capacity. Installation of optical fiber to each connection in the building facilitates upgrades of these networks, but how their capacity will be increased has not been decided. One possibility is the installation of a single fiber-based, unified ATM network that could provide each user with a dedicated bandwidth of at least 155 Mbits/sec. Because ATM provides real-time communications, it can carry high-speed digital data, as well as voice and video communications, to permit videoconferencing and other multimedia services.u

Barbara Maaskant is the director of information services at the Rollins School of Public Health, Emory University, Atlanta.

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