1.0 Introduction to computer networking
1.1.Learning objectives
after this courses the students able to
ü to assist students in understanding the benefits of networking
ü To help students place in context their current stage of networking development in their school.
ü To assist students in planning the next stage of network development in their school.
ü To provide standard networking ‘models’ and best practice to students that will assist students in their network planning.
This document includes information under the following main headings:
ü Introduction to Networking
ü Advantages of Networking
ü Types of Networks
ü Models of networking appropriate to students
ü NCTE recommendation to students
ü Some relevant terms.
This document includes information under the following main headings:
ü Introduction to Networking
ü Advantages of Networking
ü Types of Networks
ü Models of networking appropriate to students
Basic of networking
A computer network consists of a collection of computers, printers and other equipment that is connected together so that they can communicate with each other. Fig 1 gives an example of a network in a school comprising of a local area network or LAN connecting computers with each other, the internet, and various servers.
Broadly speaking, there are two types of network configuration, peer-to-peer networks and client/server networks.
Peer-to-peer networks are more commonly implemented where less than ten computers are involved and where strict security is not necessary. All computers have the same status, hence the term 'peer', and they communicate with each other on an equal footing. Files, such as word processing or spreadsheet documents, can be shared across the network and all the computers on the network can share devices, such as printers or scanners, which are connected to any one computer
Client/server networks are more suitable for larger networks. A central computer, or 'server', acts as the storage location for files and applications shared on the network. Usually the server is a higher than average
Performance computer. The server also controls the network access of the other computers which are referred to as the 'client' computers. Typically, teachers and students in a school will use the client computers for their work and only the network administrator (usually a designated staff member) will have access rights to the server.
Table 1 provides a summary comparison between Peer-to-Peer and Client/Server Networks.
Table 1: Peer-to-Peer Networks vs Client/Server Networks
Components of a Network A computer network comprises the following components:
ü A minimum of at least 2 computers
ü Cables that connect the computers to each other, although wireless communication is becoming more common (see Advice Sheet 20 for more information)
ü A network interface device on each computer (this is called a network interface card or NIC)
ü A ‘Switch’ used to switch the data from one point to another. Hubs are outdated and are little used for new installations.
ü Network operating system software Structured cabling
The two most popular types of structured network cabling are twisted-pair (also known as 10BaseT) and thin coax (also known as 10Base2). 10BaseT cabling looks like ordinary telephone wire, except that it has 8 wires inside instead of 4. Thin coax looks like the copper coaxial cabling that's often used to connect a Video Recorder to a TV.
10BaseT Cabling When 10BaseT cabling is used, a strand of cabling is inserted between each computer and a hub. If you have 5 computers, you'll need 5 cables. Each cable cannot exceed 325 feet in length. Because the cables from all of the PCs converge at a common point, a 10BaseT network forms a star configuration. Fig 4a shows a Cat5e cable, with a standard connector, known as an RJ-45 connector. Fig 4b shows a standard Cat5e Wall Outlet socket which the cables are connected to. Fig 4c shows a standard Cat5e Patch Panel Wall Outlet socket which is used to terminate the cables from various points in the school bank to a central point. Fig 4d shows a wall mounted cabinet used to house and protect patch panel cables and connectors.
What are the advantages and disadvantages of a Wireless LAN?
Wireless LANs have advantages and disadvantages when compared with wired LANs.
A wireless LAN will make it simple to add or move 10 workstations, and to install access points to provide connectivity in areas where it is difficult to lay cable. Temporary or semi-permanent buildings that are in range of an access point can be wirelessly connected to a LAN to give these buildings connectivity. Where computer labs are used in students, the computers (laptops) could be put on a mobile cart and wheeled from classroom to classroom, providing they are in range of access points. Wired network points would be needed for each of the access points.
A WLAN has some specific advantages:
ü It is easier to add or move workstations
ü It is easier to provide connectivity in areas where it is difficult to lay cable
ü Installation can be fast and easy and can eliminate the need to pull cable through walls and ceilings
ü Access to the network can be from anywhere in the school within range of an access point
ü Portable or semi-permanent buildings can be connected using a wireless LAN
ü Where laptops are used, the ‘computer suite’ can be moved from classroom to classroom on mobile carts
ü While the initial investment required for wireless LAN hardware can be similar to the cost of wired LAN hardware, installation expenses can be significantly lower
· Where a school is located on more than one site (such as on two sides of a road), it is possible with directional antennae, to avoid digging trenches under roads to connect the sites
· In historic buildings where traditional cabling would compromise the façade, a wireless LAN can avoid drilling holes in walls
· Long-term cost benefits can be found in dynamic environments requiring frequent moves and changes · They allows the possibility of individual pupil allocation of wireless devices that move around the school with the pupil. WLANs also have some disadvantages:
· As the number of computers using the network increases, the data transfer rate to each computer will decrease accordingly
· As standards change, it may be necessary to replace wireless cards and/or access points
Wireless Network Components
There are certain parallels between the equipment used to build a WLAN and that used in a traditional wired LAN. Both networks require network interface cards or network adapter cards. A wireless LAN PC card, which contains an in-built antenna, is used to connect notebook computers to a wireless network. Usually, this is inserted into the relevant slot in the side of the notebook, but some may be internal to the notebook. Desktop computers can also connect to a wireless network if a wireless network card is inserted into one of its internal PCI slots. In a wireless network, an 'access point' has a similar function to the hub in wired networks. It broadcasts and receives signals to and from the surrounding computers via their adapter card. It is also the point where a wireless network can be connected into an existing wired network. The most obvious difference between wireless and wired networks, however, is that the latter uses some form of cable to connect computers together. A wireless network does not need cable to form a physical connection between computers.
Benefits and Educational Uses
The installation of cables is time consuming and expensive. The advantages of not doing so are apparent: the amount of work required and the time taken to complete it are significantly reduced the network is accessible in places where wiring would have been difficult or impossible with no cables linking computers together, cable-related faults and network downtime are minimized. Where a wireless network is in place, teachers or students can have continuous access to the network, even as they move with their equipment from class to class. The space over which a wireless network operates is not planar but spherical. Therefore, in a multi-level site, network access is available in rooms above or below the access point, without the need for additional infrastructure. In a location within a school where network access is required occasionally, desktop computers fitted with wireless network cards can be placed on trolleys and moved from location to location. They can also be located in areas where group work is taking place. As they are connected to the network, documents and files can be shared, and access to the Internet is available, enhancing group project work. As the range of the wireless network extends outside the building, students and teachers can use wireless devices to gather and record data outside, e.g., as part of a science experiment or individual performance data as part of a PE class.
Advantages of networking students
Speed. Networks provide a very rapid method for sharing and transferring files. Without a network, files are shared by copying them to floppy disks, then carrying or sending the disks from one computer to another. This method of transferring files in this manner is very time-consuming. Cost. The network version of most software programs are available at considerable savings when compared to buying individually licensed copies. Besides monetary savings, sharing a program on a network allows for easier upgrading of the program. The changes have to be done only once, on the file server, instead of on all the individual workstations.
Centralized Software Management. One of the greatest benefits of installing a network at a school is the fact that all of the software can be loaded on one computer (the file server). This eliminates that need to spend time and energy installing updates and tracking files on independent computers throughout the building.
Resource Sharing. Sharing resources is another area in which a network exceeds stand-alone computers. Most students cannot afford enough laser printers, fax machines, modems, scanners, and CD-ROM players for each computer. However, if these or similar peripherals are added to a network, they can be shared by many users.
Flexible Access. School networks allow students to access their files from computers throughout the school. Students can begin an assignment in their classroom, save part of it
On a public access area of the network, then go to the media center after school to finish their work. Students can also work cooperatively through the network.
Security. Files and programs on a network can be designated as "copy inhibit," so that you do not have to worry about illegal copying of programs. Also, passwords can be established for specific directories to restrict access to authorized users.
Main challenges of installing a School Network
Costs although a network will generally save money over time, the initial costs can be substantial, and the installation may require the services of a technician.
Requires Administrative Time. Proper maintenance of a network requires considerable time and expertise. Many students have installed a network, only to find that they did not budget for the necessary administrative support.
File Server May Fail. Although a file server is no more susceptible to failure than any other computer, when the files server "goes down," the entire network may come to a halt. When this happens, the entire school may lose access to necessary programs and files.
Networking Models: Towards a Networked School This model shows a diagram of a networked school indicating the various types of networking models used. These include computer rooms, networked classrooms, and networked specialist rooms for specific subjects. Mobile solutions are shown in the Resource room, the General Purpose room and Building # 2. Note: To improve readability only network points are shown,
Representation of a Typical Network Model
Fig 9: Typical Network Model for a Special school. Figure 9 shows a model for a Primary or Special school. This includes connectivity to all classrooms back to a central network. The network connects to a File and Print Server. Internet access is handled via a modem or router, while internet Filtering, Proxy and Web Caching are all handled via a dedicated server.
