Monday, June 16, 2008


What is a Network?

A network is the interconnection of computers for the sharing of information and resources.

Why Network Computers?

Allow people to share information, software, and any resources, including hardware, more efficiently.

What Networking Can Do?

  • Printer sharing
  • Printer spooling
  • Disk sharing
  • File sharing

Why Network Classroom Computers?

  • Program security
  • Personal work files are much more secure
  • Reduced need for floppy disks
  • Shared files
  • Shared printers
  • Shared resources
  • Easy maintenance
Administrative networks

Using Computers for School Administration
  • Storing student demographic information
  • Scheduling students
  • Storing school-wide attendance records and generating daily attendance reports
  • Storing student achievement records and generating reports for parents
  • Generating reports for the State Department of Education

Major Benefits of Administrative Networks

  • Many people can simultaneously view and edit student records
  • Data entry can be more efficient
  • Centralized storage of student information
  • Backing-up copies of all critical information files is centralized
  • Access to productivity software is shared
  • Access to expensive peripheral equipment is shared

Major Concerns of Using Administrative Networks

  • The security of the system
  • Input errors are much more difficult to prevent
  • Considerable cost
  • In-service training for network users

Approaches to Implementing an Administrative Network

Install an "administration only" network

  • limited to a relatively small number of people
  • security of the information on the network
  • user of the network by new users can be phased in

Install a School-Wide network

  • both administrative and instructional programs will coexist
  • allow student performance results to be integrated into the administrative system for record keeping and reporting
  • attendance can be viewed and updated from anywhere in the school
  • allow electronic communication to everyone in the school
  • provide an excellent infrastructure for individualized instruction
  • entail a significant leap in sophistication and complexity, and require a great deal of planning

One of the most common mistakes school administrators make is to spend considerable amounts of money on the hardware and software for computerized administration packages, but not to budget for staff training. Training is the key component in the successful implementation of computers in school offices.

School-Wide Networks

Why Consider School-Wide Networking?

A school-wide network can be defined as a network connecting computers throughout the school, providing communication between those computers, and giving each computer access to all of the resources on the network.

  • Access for everyone -- any time, anywhere
  • Security and control
  • Ease of maintenance

Uses for a School-Wide Network

  • Networks for student learning
  • Network access to the Internet
  • Networks for school administration

Keys to successful School-Wide Networks

  • develop long-term and short-term plans
  • involve the school staff
  • has a realistic vision
  • define goals and objectives
  • determine the needs of the users
  • focus what should be done, not the technology
  • allow future flexibility while meeting present needs
  • learn from those who have designed school networks before
  • plan for the support for teachers and students, office staff and administrators, and technical support for hardware and software

Required Resources for a School-Wide Network

  • hardware
  • software
  • physical facilities
  • furniture
  • supplies
Why do we use networks in school

Computers have become an important part of today's classrooms. They are an important tool for both teachers and students. An effective way to connect these computers, and everyone using them, is to set up a network. Networks have many uses in an academic setting.

Shared resources

Local connections such as a directly connected printer or resources like printers or file servers
shared over a small LANs

Inter-Computer Communication

Some services such as Usenet News involve communications between computers where no
human operator is involved.

File transfer and Archives

Freeware, shareware, etc.

Inter-Personal Communication


Interactive Communications

Chat software: MUDS, MOOs, graphic and 3-D environments, collaborative computing

Advantages of networks

No matter what type of computer equipment you are using, installing a network will make your life as an educator run more smoothly. Current networking software provides many advantages for the educational environment.

Program Security

  • Store copies of programs in locked, read-only spaces on the server
  • Protect program files from unauthorized copying
  • Prevent tampering with programs

More Secure Personal Work Files

  • Save personal work in private spaces on hard disk
  • Password protected from inadvertent or malicious copying and/or deletion
  • No loss of information from damaged or lost floppy disks

Reduced Need for Floppy Disks

  • Floppy disks are needed only for archiving old files
  • Boot disks may be needed to start up workstations (Remote booting removes the need for boot disks.)

Shared Files

  • Share data and program files to all network users
  • Publicly accessible area to store assignments, tests, clipart, and other files
  • No copying of entire class sets of data disks

Shared Printers

  • Share the cost of printers among all users
  • Gain access to different types of printers
  • Current networking software has built-in print spooling capabilities

Shared Resources

  • Share peripheral devices
  • Access powerful information resources (CD-ROM drives)
  • Network modems to access outside resources
    • Library card catalogues
    • Databases from all over the world
    • Wire services (newspapers, radio stations, television stations)

Easy Maintenance

  • Well-planned network meets needs for several years
  • Single major task of maintenance of boot disks for workstations

Network Media

Unshielded Twisted Pair (UTP) Cable

  • consist of two insulated copper wires arranged in a regular spiral pattern to minimize the
  • electromagnetic interference between adjacent pairs
  • low frequency transmission medium
  • low cost, small size, and ease of installation
  • limited distance, usually less than 100 meters
  • the most popular and is generally the best option for school networks

    Categories of UTP Cable

Category 1 Voice Only (Telephone Wire)
Category 2 Data to 4 Mbps (LocalTalk)
Category 3 Data to 10 Mbps (Ethernet)
Category 4 Data to 20 Mbps (16 Mbps Token Ring)
Category 5 Data to 100 Mbps (Fast Ethernet)

  • Catalog 5 cable is widely used for a 10 Mbps Ethernet network
  • 10BaseT is the IEEE 802.3i standard specification for 10Mbps Ethernet transmission over UTP (Catalog 3, 4, or 5) cable
  • The standard connector for UPT cable is an RJ-45 connector, which looks like a large telephone modular connector

Coaxial (Coax) Cable

  • like the wire used to connect a TV or VCR
  • has an inner conductor surrounded by a braided mesh
  • both conductors share a common center axial, hence the term "co-axial"
  • bandwidth of up to 400 Mhz
  • highly resistant to signal interference
  • used for long distance (300-600 meters)
  • quite bulky and sometimes difficult to install
  • the most common type of connector used with coaxial cables is the BNC (Bayone-Neill-Concelman) connector

  • has two types of coaxial cable:
    Thin coaxial cable
    • refers to as thinnet
    • 10Base2 is the IEEE standard for Ethernet running on thin coaxial cable
    • the 2 refers to the approximate maximum segment length being 200 meters
    • is popular in school networks, especially linear bus networks

Thick coaxial cable

  • refers to as thicknet
  • 10Base5 is the IEEE standard for Ethernet running on thick coaxial cable
  • the 5 refers to the approximate maximum segment length being 500 meters
  • has an extra protective plastic cover that helps keep moisture away from the center
  • conductor
  • difficult to bend and install
  • used for long distance linear bus networks

Fiber Optic

  • consist of a center glass core surrounded by several layers of protective materials
  • immunity to environmental interference
  • greater capacity (bandwidth of up to 2 Gbps)
  • used for distances up to 100 kilometers
  • carry information at vastly greater speeds
  • very expensive
  • small size and lighter weight
  • difficult to install and modify, require highly skilled installers
  • adding additional nodes is difficult
  • 10BaseF refers to the specifications for fiber optic cable carrying Ethernet signals


  • use high frequency radio signals or infrared light beams to communicate between the workstations and the server
  • need transciever/antenna to send and receive data
  • widely used for connecting laptop computers to the LAN
  • expensive
  • poor security
  • slower than LANs using cabling
  • susceptible to electrical interference from lights and radios


Linear Bus (Trunkline)

  • consist of a main run of cable with a terminator at each end
  • the file server, workstations, and peripherals are connected to the linear cable
  • easy to connect a node to a linear bus
  • less expensive, require less cable
  • entire network shuts down if there is a break in the main cable
  • difficult to identify the problem if the entire network shuts down


  • each node connected directly to a central network hub or concentrator
  • a separate cable connects to each computer, and if one cable breaks, only a single computer should be affected
  • the hub or concentrator manages and controls all functions of the network. It also acts as a repeater for the data flow
  • easy to install and wire
  • no disruptions to the network when connecting or removing devices
  • easy to detect network problems
  • more expensive, requires a hub and more cable length than a linear bus topology
  • all nodes shut down if the hub or concentrator fails

Star Wired Ring (Token Ring)

  • developed by IBM
  • employ a special coded message called a token that the operating software passes in sequence to each computer on the network
  • created for IBM-compatible computers
  • 4 or 16 Mbps using twisted pair


  • similar to a bus, except the electrical signal is routed through each computer as it moves along the line
  • easy to install
  • entire network shuts down if there is a problem on a node
  • mainly used on the Macintosh network
  • slow
  • not practical in multi-room network installations

Network Hardware

File Server

A File server is a high capacity computer that provides various resources to the network.
the heart of a network

  • need a very fast computer with a large amount of RAM and storage space, a fast network interface card, and a tape back-up device
  • need network operating system such as Novell Netware, Windows NT server, or Apple Share
  • control the communication of information between the nodes on a network


A computer in a network is called workstation or client.

  • a computer connected to a network
  • need a network interface card
  • not necessarily need floppy disk drives or hard disks since files can be saved on the file server

Network Interface Cards (NICs)

NIC provides the link between your computer and your network.

  • provide the physical connection between the network and the workstation
  • most are internal, with the card fitting into an expansion slot inside the computer
  • some build on the motherboard
  • affect the speed and performance of a network
  • three common network interface connections: Ethernet cards, LocalTalk connectors, Token Ring cards


A hub is a device whose primary function is to send and receive signals along the network between the nodes connected to it.

  • connect multiple devices to the network
  • commonly found in star and star-wired ring topology networks
  • entire network shuts down if there is a problem on a hub
  • serve as a central meeting place for cables from computers, servers and peripherals
  • usually configured with 4, 8, 12, or 24 RJ-45 ports


A repeater is a device that regenerates and amplifies signals to create long-distance networks

  • simply receive, amplify and rebroadcast the signals
  • some repeaters provide basic error-checking
  • can be separate devices or they can be incorporated into a concentrator
  • inexpensive, used to overcome distance limitations


A bridge is a device that links two homogenous packet-broadcast local networks. It accepts all packets from each network addressed to devices on the other, buffers them, and retransmits them to the other network.

  • connect two or more networks using the same address method or protocol
  • can provide some addressing information
  • monitor and manage the traffic to maintain optimum performance on both sides of the network
  • often used when LANs reach their capacity of nodes


A switch is a high-speed multiport bridge. Today, switches are replacing multiport repeaters or concentrators in a UTP environment.

  • an intelligent hub that maintains a bridging table, keeping track of which hardware addresses are located on which network segment
  • more efficient than with any other type of hub
  • ability to dedicate bandwidth to each port on the switch


Routers are similar to bridges in that they link two or more physically separate network segments. The network segments linked by a router, however, remain logically separate and can function as independent networks.

  • translate information from one network to another; similar to a super-intelligent bridge
  • maintain a map of the network, select the best route for data
  • access to more network level knowledge than is available to bridges
  • information on source addresses, destination addresses, path distances, and in some cases,
  • segment bandwidth and segment status are contained in the router's routing table
  • translates local addresses (eg. "spot") into network addresses (eg.
  • can translate messages with different addressing methods
  • can act as firewalls (many ISP's block traffic at the router level)
  • direct signal traffic efficiently
  • route messages between any two protocols
  • can route messages between linear bus, star, and token ring topologies
  • can route messages across fiber optic, coaxial, and twisted-pair cabling

Network Operating System

A network operating system is a supervisory software program that resides on the server. It controls how the network operates by defining who can use the network and how information and peripherals are shared among users.

Novell Netware

  • most popular
  • good solution of a PC and Mac network

Microsoft Windows NT

  • getting popular
  • good solution of PC networks
  • easier to set up than Novell Netware


  • Macintosh only
  • does not scale to fit a large network

Media Access Method

How computing devices access the network cable and send data is known as the media access method. There are four commonly used media access methods: Ethernet, Token Ring, Local Talk, and FDDI.


  • most popular media access method
  • use access method called CSMA/CD (Carrier Sense Multiple Access/Collision Detection)
  • allow for linear bus, star, or tree topologies
  • transmit data over UTP, thin-coaxial, thick-coaxial and fiber optic cables at rates of 10 Mbps
  • Fast Ethernet supports 100 Mbps, but requires faster hubs and network interface cards

Token Ring

  • developed by IBM in the mid 1980s
  • use a star-wired ring topology over shielded and unshielded twisted-pair wiring
  • a central hub (referred to as a "MAU" Mutlistation Access Unit) is at the center of the ring
  • Two versions of Token Ring: 4 Mbps and 16 Mbps
  • use a token passing process to circulate packets around the ring.
  • more expensive than Ethernet
  • good option for PC networks

Local Talk

  • developed by Apple Computer, Inc. for Macintosh computers
  • best suited to small networks of Macs
  • allow for linear bus, star, or tree topologies using twisted pair cable
  • up to 32 devices (computers, printers, and file server)
  • slow, data transmits at only 230 Kbps
  • use the CSMA/CA (Carrier Sense Multiple Access with Collision Avoidance) process for transmitting data. CSMA/CA is similar to CSMA/CD
  • single network can be up to 1,000 feet (305 meters)

FDDI (Fiber Distributed Data Interface)

  • ANSI standard
  • use fiber optics for speeds of up to 100 Mbps
  • use primarily to interconnect two or more LANs, often over long distances
  • also employ Token Ring passing process to transmit data; but use a dual counter-rotating ring topology, meaning there are two rings of cable with two tokens circulating in opposite directions
  • use a token passing process to circulate packets around the ring


10Base2 - Ethernet specification for thin coaxial cable, transmits signals at 10 Mbps (megabits per second) with a distance limit of 185 meters per segment.

10Base5 - Ethernet specification for thick coaxial cable, transmits signals at 10 Mbps (megabits per second) with a distance limit of 500 meters per segment.

10BaseF - Ethernet specification for fiber optic cable, transmits signals at 10 Mbps (megabits per second) with a distance limit of 1000 meters per segment.

10BaseT - Ethernet specification for unshielded twisted pair cable (category 3, 4, or 5), transmits signals at 10 Mbps (megabits per second) with a distance limit of 100 meters per segment.

Backbone - A cable to which multiple nodes or workstations are attached.

Cable - Transmission medium of copper wire or optical fiber wrapped in a protective cover.

Coaxial cable - Cable consisting of a single copper conductor in the center surrounded by a plastic layer for insulation and a braided metal outer shield.

E-mail - Electronic mail. Messages sent through a computer network; they may also include graphics and files.

Ethernet - The world's most popular networking system. Designed to run all popular network protocols, Ethernet is used on over 40 million computers worldwide. With a transfer speed of 10 million bits per second. Ethernet is the least expensive high speed LAN alternative.

FTP - File Transfer Protocol. The Internet protocol (and program) used to transfer files between hosts.

Fast ethernet - A new Ethernet standard that supports 100 Mbps using category 5 twisted pair or fiber optic cable.

Fiber optic cable - A cable, consisting of a center glass core surrounded by layers of plastic, that transmits data using light rather than electricity. It has the ability to carry more information over much longer distances.

File server - A computer which contains files that can be used by everyone connected to the network.

Hub - A hardware device that contains multiple independent but connected modules of network and internetwork equipment. Hubs can be active (where they repeat signals sent through them) or passive (where they do not repeat but merely split signals sent through them).

Internet - A global network of networks used to exchange information using the TCP/IP protocol. It allows forelectronic mail and the accessing and retrieval of information from remote sources.

LAN - Local Area Network. A network connecting computers in a relatively small area such as a building.

mbps - MegaBits per Second. A unit showing the speed of a network.

Network interface card (NIC) - A board that provides network communication capabilities to and from a computer.

Network operating system (NOS) - Operating system which runs on the file server designed to pass information and communicate between more than one computer. Examples include AppleShare, Novell NetWare, and Windows NT Server.

Novell - The company which makes Netware, the most commonly used network server software for IBM computers.

Operating system - the software of a computer which controls the execution of programs.

Peripheral - A device attached to a computer, I. E. printer, modem, CD-ROM etc.

Port - A connection point for a cable.

RJ-45 - Standard connectors used for unshielded twisted-pair cable.

Repeater - A device used in a network to strengthen a signal as it is passed along the network cable.

Router - A device which connects two networks and permits packets of information to move between networks only if necessary .

Server - A computer providing a service to network users.

Speed of Data Transfer - The rate at which information travels through a network, usually measured in megabits per second.

Terminator - A device that provides electrical resistance at the end of a transmission line. Its function is to absorb signals on the line, thereby keeping them from bouncing back and being received again by the network.

Topology - Physical topology of a network refers to the configuration of cables, computers, and other peripherals. main types of physical topology are: linear bus (backbone), star, star-wired ring, and hybrid. Logical topology is the method used to pass the information betweenworkstations. Examples are: Ethernet, AppleTalk, Token Ring, and TCP/IP.

Twisted pair - Network cabling that consists of four pairs of wires that are manufactured with the wires twisted to certain specifications. Available in shielded and unshielded versions.

WWW - World Wide Web is comprised of millions of documents, stored on computers on the Internet. The documents are all linked together and make up most of the information available on the Internet.

WAN - Wide Area Network. A communications network which connects together a number of local networks.

Workstation - A computer connected to a network which is used by a person to run application programs.


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