Thursday, January 15, 2009

Network Interface Card (NIC)

A NIC (pronounced 'nick') is also known as a network card. It connects the computer to the cabling, which in turn links all of the computers on the network together. Each computer on a network must have a network card. Most modern network cards are 10/100 NICs and can operate at either 10Mbps or 100Mbps.Only NICs supporting a minimum of 100Mbps should be used in new installations schools. Computers with a wireless connection to a network also use a network card (see Advice Sheet 20 for more information on wireless networking).

Hub and Switch

A hub is a device used to connect a PC to the network. The function of a hub is to direct information around the network, facilitating communication between all connected devices. However in new installations switches should be used instead of hubs as they are more effective and provide better performance. A switch, which is often termed a 'smart hub'.

Switches and hubs are technologies or ‘boxes’ to which computers, printers, and other networking devices are connected. Switches are the more recent technology and the accepted way of building today's networks. With switching, each connection gets "dedicated bandwidth" and can operate at full speed. In contrast, a hub shares bandwidth across multiple connections such that activity from one PC or server can slow down the effective speed of other connections on the hub.
Now more affordable than ever, Dual-speed 10/100 autosensing switches are recommended for all school networks. Schools may want to consider upgrading any hub based networks with switches to improve network performance – ie speed of data on the network.

Wireless Networks

The term 'wireless network' refers to two or more computers communicating using standard network rules or protocols, but without the use of cabling to connect the computers together. Instead, the computers use wireless radio signals to send information from one to the other. A wireless local area network (WLAN) consists of two key components: an access point (also called a base station) and a wireless card. Information can be transmitted between these two components as long as they are fairly close together (up to 100 metres indoors or 350 metres outdoors). Suppliers would need to visit the schools and conduct a site survey. This will determine the number of base stations you need and the best place(s) to locate them. A site survey will also enable each supplier to provide you with a detailed quote. It is important to contact a number of different suppliers as prices, equipment and opinions may vary. When the term 'wireless network' is used today, it usually refers to a wireless local area network or WLAN. A WLAN can be installed as the sole network in a school or building. However, it can also be used to extend an existing wired network to areas where wiring would be too difficult or too expensive to implement, or to areas located away from the main network or main building. Wireless networks can be configured to provide the same network functionality as wired networks, ranging from simple peer-to-peer configurations to large-scale networks accommodating hundreds of users.

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 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 schools, 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:

• It is easier to add or move workstations
• It is easier to provide connectivity in areas where it is difficult to lay cable
• Installation can be fast and easy and can eliminate the need to pull cable through walls and ceilings
• Access to the network can be from anywhere in the school within range of an access point
• Portable or semi-permanent buildings can be connected using a wireless LAN
• Where laptops are used, the ‘computer suite’ can be moved from classroom to classroom on mobile carts
• 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 fa├žade, 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
• Lower wireless bandwidth means some applications such as video streaming will be more effective on a wired LAN
• Security is more difficult to guarantee, and requires configuration
• Devices will only operate at a limited distance from an access point, with the distance determined by the standard used and buildings and other obstacles between the access point and the user
• A wired LAN is most likely to be required to provide a backbone to the wireless LAN; a wireless LAN should be a supplement to a wired LAN and not a complete solution
• Long-term cost benefits are harder to achieve in static environments that require few moves and changes
• It is easier to make a wired network ‘future proof’ for high data transfer.

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.
Wireless Network ConfigurationsWireless networks can be configured in an ad hoc/peer-to-peer arrangement or as a local area network.
Ad Hoc/Peer-to-Peer ConfigurationThis is the most basic wireless network configuration. It relies on the wireless network adapters installed in the computers that are communicating with each other. A computer within range of the transmitting computer can connect to it. However, if a number of computers are networked in this way, they must remain within range of each other. Even though this configuration has no real administration overhead, it should only be a consideration for very small installations.
Benefits and Educational UsesThe 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 minimisedWhere 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.
Technical and Purchasing ConsiderationsNetwork interface cards for wireless networks are more expensive than their wired counterparts. The cost of the access points has also to be considered. Wireless networks work at up top 54Mbps, whereas wired networks normally work at 100Mbps (Fast Ethernet). This data transmission rate is dependant on the number of users, the distance from the access point and the fabric of the building (metal structures in walls may have an impact). A wireless network will be noticeably slow when a group of users are transferring large files. This should be considered if multimedia applications are to be delivered over the network to a significant number of users. As the range of the network may extend beyond the walls of the building, it can be accessed from outside. Consideration should be given to what security features the equipment provides to ensure that only valid users have access to the network and that data is protected.

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