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Local Area Networks for K-12 Schools
Author: Tim Lederman
What is a LAN?
A Local Area Network (LAN) allows computing equipment to share information from any device on a network with other devices on the same network, and includes cabling, network transmission devices, network interfaces, and computing devices. Some examples of computing devices on a LAN include:
Different kinds of computers use different methods, or protocols, to communicate with each other. Macintosh computers use the AppleTalk protocol. Macintosh as well as PCs can use TCP/IP to share information on the Internet. Some PCs require a Network Operating System (NOS) to communicate. For example, Novell Netware is a popular NOS with PC users.
Servers and Clients
A server computer provides a special service (examples described above) while a client computer requests and receives a service from a server. The same computer could be a client or a server, depending upon the type of data communications taking place. For example, a computer could serve one of its files to another computer, but it could also receive a file from that computer.
Uses for LANs in a School Building
Uses for LANs District Wide
District uses for LANs include all of the above, but in particular:
Note: The interconnection of multiple building LANs is often accomplished by Wide Area Networking (WAN) through radio transmission or through leased data lines from a telephone company.
Types of LANs
Common types of LAN hardware are Ethernet and Token Ring. Ethernet predominates because it is easily designed and is composed of data transfer devices which are less expensive than similar Token Ring devices. The performance of Ethernet and Token Ring are roughly the same in most situations. While it is possible to interconnect Ethernet and Token Ring networks in the same location, it adds to cost and complexity. It is best to keep the configuration of a school's data communication infrastructure as simple as possible. Another standard for data communication is ATM (Asynchronous Transfer Mode). It is more expensive than Ethernet or Token Ring but allows higher speeds and will eventually allow better integration of computer-data, digitized voice (telephone), and video. Some suggestions for choosing a LAN include:
Cabling medium. The most cost-effective cabling is Category 5 twisted-pair cable. This cable works with standard Ethernet (10 Million bits per second, 10Mbps) and "fast" Ethernet (100 Mbps), and is capable of speeds up to 150 Mbps with existing technology. This has become the cable of choice in most LAN designs. Fiber-optic cable transmits more data, but materials and installation are much more expensive. Proper installation of fiber-optic cable is difficult in an old building because the cable should not be bent during installation or when finally terminated (an 8" minimum bending radius is allowed).
Wiring plan. The location of wiring cabinets/closets is dependent on suitable locations in the building and distances between computers. The maximum distance between a computer and a network wiring cabinet/closet is 10 meters. A refrigerator-sized cabinet where cables come together and network transmission equipment (and sometimes servers) are stored can be enclosed with doors and stand in a large room, or it can be placed as an open rack in a small room or closet. Wiring cabinets/closets can be interconnected with twisted-pair cable, but fiber-optic cable is a better choice for a variety of reasons, especially higher speed.
Number of network connections (plug-in points) per room. Every computer needs a network connection and each connection is comprised of (1) a plug-in point in the wall of the room, and (2) wiring from this point to the wiring cabinet/closet. Short and long term technology goals need to be considered when planning the number of network connections per room.
Additional things to remember when designing a school's LAN
Network outlets. Locate near the area where the computers are /will be located.
Electrical outlets. Locate near the network outlets. If electrical outlets are installed for future use, be sure the building's power supply and power distribution infrastructure is adequate to handle the added computers. Because the cost of providing electrical service can be substantial (as much as half of the cost of a LAN itself), it is prudent to consider this cost at the same time as estimating the cost of the LAN.
Furniture and fixtures location. When developing a wiring plan, consider the placement of furniture and stationary fixtures.
Wiring. When wiring for a LAN, run additional cabling for other purposes at the same time because the cost benefits are often substantial. The installation of cabling for the following purposes should be considered when installing LAN cabling :
Potential use of space. Include every room in the LAN design which might ever house a class, group, or office. It is much less expensive to design and install a network for an entire building than it is to "modularize" into smaller LAN projects (classrooms in one project and offices in another project). Room use may change over the years (large closets may become offices or small classrooms, for example).
There are many aspects of LAN design to consider when developing a technology plan for a school building or school district. This digest has indicated several key design issues, however one should contact an experienced consultant or network designer before finalizing a LAN design.
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This Digest was prepared for the ERIC Clearinghouse on Information & Technology by Tim Lederman, Professor of Computer Science, Siena College, Loudonville, New York. email@example.com
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