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Wireless networks can support excellent learning opportunities and deliver a Broadband Service to areas of a school where a "wired to desk" topology infrastructure would be impossible to achieve. Examples include the centre of a large hall, a large library area, mobile learning units, or even the school playing field. It needs to be clearly understood that wireless access systems use "shared" bandwidth and are hub based. They are therefore susceptible to multiple collisions under heavy load. They should be used to complement the network system rather than be the primary means of network communications for a whole site. Wireless access points should be located at back areas of the network.
There are three basic types of wireless access standards in general usage. The first of these is IEEE802.11b and has a connection speed of up to 11Mbps between the device and the wireless access point. However, the bandwidth for communication across this link will be half of the speed proclaimed and will be limited to a maximum of 5.5Mbps.
The second type of access point uses a higher speed and is compatible with older 802.11b systems, known as IEEE802.11g. This type of access point has a communications speed of up to 54Mbps and as with the 802.11b devices, the communications bandwidth will be half of this at 27Mbps.
802.11g and 802.11b devices cannot be mixed and retain the higher speeds, as the access point will default to the lower speed 802.11b standard.
The third protocol is IEEE802.11a, which is not backwardly compatible with 802.11g or b devices. Operating at 5Ghz rather than 2.4Ghz the penetration and durability of the signal is not as robust as 802.11g but allows for a greater access point density for any given area. Where in reality 802.11g and b access points have only 3 unique channels the 802.11a chooses from 8 available channels.
Both of the above devices have to conform to ETSI standards for radio network transmissions and are only allowed to irradiate their signal using a maximum specified power output. As this will greatly affect the range of the wireless network, both 802.11 standards compensate for weaker received signals by offering lower bandwidths as the signal becomes weaker. This can reduce to a mere 500Kbps before the signal becomes too weak to achieve a locked connection.
It is difficult to identify which of the two types is best for any given purpose. As a general rule IEEE802.11g should be chosen as a preference over IEEE802.11a.
For both types it is advisable to engage the services of the Local Authority, or trusted infrastructure supplier and undertake a detailed radio site survey. This will identify areas where additional wireless access points would need to be located in order to ensure that the intended area of usage is covered. It is best to avoid any supplier that reports the need to swamp an area with multiple wireless access points in too close a proximity. The radio channels these devices use are limited and will result in the devices fighting for control. If a greater range is required, consider using specialist antennas to direct signals into a room or area. Sector panel or flat plate antennas are best for this purpose.
When purchasing any wireless access point, ensure that it meets four basic requirements:
(1) It is possible to turn off the devices SSID (Service Set Identifier), sometimes known as beaconing, in order to prevent undesirable visibility of the wireless access points to any visiting wireless device (either invited or otherwise). If beaconing is switched off, ensure that the SSID has been entered manually on the wireless network cards parameters. Otherwise operating systems, such as Windows XP, will be attracted by any nearby wireless networks that are "beaconing".
(2) The Wireless Access Point device supports encryption of transmitted data using a system known as WEP (Wired Equivalent Protocol) with at least 128bit encryption strength. An encryption standard known as WPA is replacing WEP as the standard for wireless security so the chosen device should support this method of security.
(3) The Wireless Access Point uses MAC address filtering in order to access only those network devices allowed to use the wireless network. Every computer network card, wireless network card and removable wireless network interface has a unique MAC (Media Access Control) address that details its manufacturer and other information.
(4) The Wireless Access Point can have additional antenna support. Ideally the type of access point chosen will have two standard TNC or Reverse SMA type "rubber duck" antennas. These deliver the signals transmitted at a quarter wavelength apart. This helps in achieving a connection should one of the antennas be masked from a computer or laptop wireless receiver's view.
If this guidance is followed it should ensure that your wireless network is anonymous (by SSID suppression), secured (by WEP or WPA encryption) and limited (by MAC address permissions). However, all the above can be circumvented with a great deal of patience and suitable wireless packet sniffing devices. In order to provide another level of security, consideration should be given to further measures.
Connect up all the wireless access points to their own VLAN and use RADIUS authentication. Do not use DHCP from a WAP and ensure that Internet or server access requires rigorous authentication. To improve security, connect the wireless access points to a digital timer, which cuts power to the device during out of school hours and weekends.
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Labels: eSecurity
