Scalability in K-12 Networks

• 06/01/99

That scheme is called scalability. Scalability refers to network growth both in terms of the number of users as well as new applications in need of more bandwidth. K-12 education is one of the great users of bandwidth. Throughout the brief history of educational computing, teachers and students have seen and used the potential of graphics, video, the Internet, home-page development and conferencing in the learning process. In many districts, teachers somehow manage to utilize all the bandwidth available to them - and then look for more.

"Network-based learning technologies have been slow to evolve due to the unusual nature of developing infrastructure services," wrote Professor R. William Maule, of the University of San Francisco. "However, advanced communications technologies can greatly enhance instructional programs and are necessary to support future workers in a highly competitive global economy." A scalable network brings the learning resources of the world into the workstations of individual students almost instantaneously, in accordance with the latest technology.

If the district network designers have incorporated scalability in their thinking, they can deploy new bandwidth technology at the point at which it becomes affordable. They do not have to re-do or re-install that which they have already done. They do not have to retrain staff. Existing management systems can be maintained. The designers build incrementally and thus cost-effectively, because they know that they are on a coherent migration path.

Scalability is an issue that should be discussed in as much detail as possible in a district's technology plan. This alerts the administration and board to budget resources for the future, and indicates to all teachers how and when they will receive the new allocations of technology.

Switching

Switching is key to scalability because it represents a dramatic upgrade from shared technology that relies on hubs and routers, to switched technology. In shared technology all end users share 10 Mbps of bandwidth. Shared technology is often a source of frustration for teachers: it may take minutes for students to get on the Net and/or to reach their assignments. In a K-12 setting, students often use the same programs at the same time, and this severely challenges a shared technology network.

In switched technology, every end user receives dedicated 10 Mbps, or even 100 Mbps access. The difference between shared and switched networks for the end user is dramatic. Tasks can be accomplished much faster because of the increased dedicated bandwidth to the workstation.

The transition from shared to switched can be achieved with virtually no backtracking of the infrastructure. It merely involves switches, which, at least in the case of 3Com, are now affordable. 3Com develops and prices its switches with scalability specifically in mind. If a coordinator is not actively considering switched technology, his or her approach is incomplete, indeed obsolete. If switching is not under current consideration, the network cannot meet the test of cost-effectiveness.

The following are the key elements of the switched network:

1. 10/100 Network Interface Cards for the desktop and the server.
2. 10/100 Switches placed at strategic points to accommodate bandwidth and eliminate bottlenecks.
3. Fiber optic backbones throughout the district.
4. Gigabit switches for large districts or those ready for major bandwidth.
5. Software that provides complete management of the network, including routing, security and remote monitoring.

Ethernet

Ethernet is the standard data link protocol that specifies how data are placed on, and retrieved from, a common transmission medium. It is the underlying transport vehicle used by several upper-level protocols, including TCP-IP. Fast Ethernet is the step up. It is 100 Mbps technology based on the 10BASE-T Ethernet CSMA/CD network access method. Fast Ethernet is a highly popular, high-speed technology because of its cost-effectiveness, stability and compatibility with existing Ethernet environments. One switch can support both Ethernet and Fast Ethernet traffic, delivering high bandwidth to the desktop, aggregating 10/100 Mbps hubs, and maintaining the status quo for those who are efficiently served by shared technology.

Gigabit Ethernet, even though it retains traditional simplicity and manageability of Ethernet and Fast Ethernet, allows a tenfold increase in backbone bandwidth with minimal impact on support staff. The new bandwidth helps the district cope with unplanned changes and additions to the network, and relieves staff from constantly having to tune the network. Gigabit is currently being used primarily for fiber backbones, but advances are soon forthcoming that will bring it to the workstation, using twisted pair cabling. Ethernet/Fast Ethernet/Gigabit Ethernet is a logical and affordable progression that will assure cost-effective scalability.

In conclusion, scalability allows district technology coordinators to provide their teachers and students maximum utilization of networking technology: farther and faster reaches to stretch the minds and horizons of those who seek to learn.

Thomas A. Vonder Haar is director of research, and Dominic M. Mayer is vice president and head of the design department of The Computer Junction, Inc., in Washington, Mo. The Computer Junction is a K-12 networking company.