A to Z
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Ad Hoc Network or Ad Hoc Mode The configuration of a wireless network that allows communications directly from one user device to another without the need to travel through a base station. It includes two or more wireless stations with no access point. The rationale behind ad hoc networks is the ability to setup a wireless network quickly, for example to setup a wireless network for a conference room meeting. Another user of ad-hoc wireless networks would be emergency rescue teams who use them for a simple and fast form of communication where there is no time to setup cabling and other networking hardware. See also Infrastructure Mode |
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Antenna Diversity To mitigate the effects of multi-path, many APs and network cards use two separate antennas to create antenna diversity. The receiver compares the strength of the signal from each antenna and automatically selects the best one. Antenna diversity can be very useful in environments where there is a lot of RF interference or object interference. See also MiMo |
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Architecture The architecture of a wireless network describes the interconnection of primary components that provide major functions, including signal coverage, data throughput and security. Before any wireless network is deployed the requirements and use of the network must be taken into account and understood. The primary use or purpose of the network will be a key determinant in choosing which architecture is deployed. Common types of architecture include Autonomous Access Point Architecture, Controller-Based, Mesh Network and Ad-Hoc. |
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Authentication The process of proving the identity of a user or base station. The use of usernames and passwords is probably one of the most common authentication methods, but many other more complex authentication types are available. For example, digital certificates can offer a means of authentication without user intervention. |
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Beam Antenna see Yagi Antenna |
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Bluetooth A specification based on the IEEE 802.15 standard. Bluetooth is a short to medium range network and offers a range of approximately 3 feet. Bluetooth has negated the need for USB and serial connections where there are relatively low data rates. Bluetooth operates in the 2.4GHz band using FHSS. |
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Brute Force Attack When a hacker uses every possible means at his disposal to break into a secured system or network, this is known as brute force. For example, a hacker might attempt to break a cryptographic key by trying every possible combination. |
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Bridge A wireless bridge connects two network segments together. Up until late 2001, most wireless bridge devices were dedicated devices. Now most wireless AP’s can be put into bridge mode. Most wireless bridges are used to connect two buildings. Most dedicated bridges will allow you to configure them to accept clients to connect to them directly. This is not recommended unless absolutely necessary. Bridges are primarily for bridging data traffic not for wireless client connectivity. |
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Co-Channel Interference A phenomenon where transmissions from one wireless network bleed into the range of other devices on the same channel causing interference. In wireless network design, the effects of co-channel interference can be mitigated by isolating individual access points from one another by the use of non-overlapping channels and by using environmental attenuation strategically (walls, filing cabinets, etc) |
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Channel Bonding 802.11n networks can operate in a 40Mhz channel by bonding two 20 Mhz channels together which significantly increases throughput. |
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Data Rate Switching If the data rate is high and a station is far away from the AP, it can result in the data being retransmitted in order to reduce frame corruption. Eventually, it will result in too many retransmissions that the actual throughput is greatly reduced. These retransmissions affect other wireless stations as well since the wireless medium or airspace is being cluttered by retransmissions. In order to prevent this, DRS adjusts the data rate to a lower level and provides an overall benefit to all connected devices. |
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Digital Certificate Some wireless networks will require a digital certificate pre-installed on user devices before users are allowed full access to the wireless network. A digital certificate combines an encryption key with information that helps validate the identity and integrity of that key. |
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Directional Antenna see Yagi Antenna |
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DMZ (Demilitarized Zone) Refers to a network (local area network) that has secured or protected access to the Internet. All traffic to the DMZ is regulated by a firewall so the LAN remains protected from outside attacks. The DMZ host is the computer which has a direct connection to the internet. |
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DNS Domain Name System. A TCP-IP protocol that translates user-friendly names of websites or devices into an IP address. |
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DHCP (Dynamic Host Control Protocol) One of the biggest problems facing network administrators is keeping track o fall those IP addresses and who has what. The Dynamic Host Configuration Protocol was designed to alleviate most, if not all of those problems by automatically assigning IP address to client devices. |
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Dual Wan Router A router which allows connectivity to two separate ADSL lines. The big advantage of using a dual wan router is increased speed and improved redundancy. If one ISP suffers an internet blackout, and you are subscribed to another ISP, users will still have internet connectivity. |
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Express Card About half the size of an PCMCIA card, the express card is generally perceived as the successor to the PCMCIA client card technology. An example of an express card would be the Belkin N 1 Wireless Express Card. |
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ESSID When a wireless network has two or more access points, the ESSID is the identifying name of a wireless access point. |
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Ethernet over Power (a.k.a Homeplug) The transmission of data packets over AC powerlines. The setting up of a powerline network requires no new cables to be setup, as the electrical wiring is already available from power sockets. The electrical meter acts as a firewall as it strongly attenuates the signal. Not to be confused with Power over Ethernet. |
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Ethernet Repeater A device which receives an incoming signal from one cable and transmits it out to another cable run. This can be used to extend the range of a wired network or the range of a wired access point. |
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Hacker An individual with in-depth knowledge of computer systems. Hacking can be done as a hobby with completely benign motives, this is known as white-hat hacker. Or, an individual may perform hacking for more sinister purposes, (black hat hacking). |
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Half-Duplex Transmissions that occur in both directions but only one way at a time. |
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Hertz A standard measurement of frequencies. One cycle in one second is equal to one hertz. Therefore, 1,000,000 hertz is one million cycles in one second. |
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Hidden Node Problem Hidden nodes are clients that can be seen by the AP and can see the AP but cannot see or be seen by one or more of the other clients. Because of this scenario, the hidden nodes cannot hear the other clients or at least one of the other clients communicating and may attempt to communicate while the other nodes are active. Hidden nodes normally occur because of some large obstacle such as a solid wall or insufficient transmit power. |
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Homeplug Networking |
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Frame Acknowledgment All transmitted data frames must be acknowledged. If part of the data frame transfer is fails, the frame is considered lost. The station which sends the frame must receive an acknowledgment or the data frame is considered lost. Positive acknowledgments are the only indication of success. |
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Free Radius A widely deployed free version of RADIUS server that runs on UNIX |
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Infrastructure Network Infrastructure networks have one or more access points that are almost always connected to a wired network. Each wireless station exchanges messages and data with the access point, which relays them to other nodes on the wireless network or the wired LAN. Any network that requires a wired connection through an access point such as a printer, a fileserver, or an Internet gateway is an infrastructure network. |
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Inter-Access Point Protocol A roaming protocol as certified by the Wi-Fi Alliance which enables users to move through a building while maintaining a connection to a network via multi-vendor access points. |
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Internet Authentication Service Authentication Service that is part of Windows Server 2003. When IAS is part of an Active Directory Domain, it uses that same set of credentials as used by network access control. For Windows Server 2008, Microsoft replaced IAS with Network Policy Server. |
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Low-Loss Cable Cable used to connect an access point to an antenna. Typically .04 inch. See also Thin Cable |
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MAC address A unique identifier of network hardware devices. During data transfer, the router or AP will check the MAC address agrees with the physical destination address of the packet. If accepted, the data packet gets authorisation to be sent. |
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Mimo (Mutiple Inputs Mutiple Outputs) A technology, upon which 802.11n is based that takes advantage of the detrimental problem of multipath to create more data bandwidth in wireless networks by reducing bit error. A Mimo enabled device can process each RF chain from each antenna separately. This can dramatically improve throughput. Mimo antenna configurations are often described with the shorthand “YxZ” where Y and Z are integers used to refer to the number of transmitter antennas. |
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Mulit-path Interference Multi-path loss happens when a signal reaches a receiving antenna directly from a transmitter and again a fraction of a second later bouncing off a reflective surface. An example of this happens with analogue broadcast television where multipath appears on the screen as a shadow image. In a wireless network, the receiver treats multi-path as noise, which reduces network speed. |
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NAT A routers NAT firewall prevents unrequested data from the WAN side of router flowing to the LAN side. An NAT is your first barrier protecting your network from the rest of cyberspace. |
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Omni Directional Antenna Antennas that transmit radio energy in a donut fashion around the antenna. Omnidirectional antennas are typically used for better ceiling-to-floor coverage. Typically, there are two variants of this type of antenna – high-gain and low-gain. High-gain usually means increased horizontal bandwidth with a drop in vertical coverage and the ability of more users to share the bandwidth. Whilst low-gain antennas will have less coverage and will limit the number of users in the coverage zone. |
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Parabolic Antenna A type of antenna resembling a mini-satellite dish. Parabolic antennas have very high gains up to 24-25dBi for 802.11. Very narrow but focused area of coverage. Usually used for bridging two networks e.g. from one building to another. Some parabolic antennas have beam widths of only 6 degrees. This makes accurate positioning of them to be of paramount importance. |
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Power over Ethernet (PoE) A technology that allows for the transmission of power over standard Ethernet cables. PoE can be used to power access points and other wireless devices in locations where local power outlets are not available. |
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Port Forwarding A technique for putting a node such as a PC outside control of your NAT. Typically, this is used for gaming, downloading torrents or setting up the PC as a HTTP of FTTP web server. |
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Quality of Service (QoS) Wireless lan specification which allows for prioritisation of data packets |
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Roaming In it’s purest sense roaming is the ability of devices to connect from multiple access points without the user having to manually login or logoff networks. For roaming to be successfully implemented all SSID’s should be the same, all of the networks are on non-overlapping channels, the router is using DHCP and all networks in the roaming area share the same encryption keys. |
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Repeater A repeater regenerates radio signals to extend the range of a wireless network. In certain circumstances (such as low data throughput networks) wireless repeaters can be an effective solution to overcome signal attenuation. However, the downside of using a wireless repeater is that it will reduce throughput of your wireless network by roughly 50 per cent. A repeater must receive and retransmit each frame on the same RF channel, which effectively doubles the number of frames sent over the network. |
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Request to Send/Request to Clear Handshaking A protocol to minimize collisions among hidden stations. Imagine there are two wireless stations X and Z. Station X and Station Z cannot hear each other due to object interference but they can communicate with the same access point. Because of this situation X can begin sending a frame without noticing that Z is already transmitting. This can cause a collision between Station X and Station Z to occur at the access point. This results in possible data corruption and the need to retransmit their respective packets. However, if either Station X or Z, uses RTS/RTC, the collision will not happen. Before transmitting, Station Z will send an RTS frame to the access point and receive a CTS frame from the access point in response. |
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RF Generator An RF generator is a device used to generate RF noise within specific frequency ranges. They are used to test RF behaviour in different spaces. See also WiFi Jammer |
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RF Interference Bluetooth and microwaves can all attenuate your wireless signals. RF interference does not come from other Wi-Fi Networks alone. The technician also has to take into account interference from 2.4Ghz cordless phones, microwave ovens, water pump motors, lift motors and other unlikely sources. |
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Rogue Access Point An access point setup by a hacker for the purposes of data sniffing is considered to be a rogue access point. For many users, in unfamiliar surroundings, the SSID of the rogue AP can easily be perceived as genuine. |
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Signal to Noise Ratio Ratio of the wireless signal to RF energy noise in an environment. An SNR ratio of 11dB to 20dB is considered good whilst 29dB or above considered outstanding. |
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Signal Strength Signal strength is the amount of power in the radio signal that the adaptor received during the most recent scan. Many programs use the familiar five bars to display signal strength. It is important to note that apparently good signal strength does not always equate with good signal quality. Signal quality is the quality of the data packets received during the most recent scan. That is why most wireless network management programs show separate readings for signal strength and signal quality. If the signal is strong but the quality is poor, it is possible there is some RF interference at play. If the signal quality and signal strength is low, the user might be too far away from the access point or there object interference. |
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Spectrum Analyzer A spectrum analyzer is used by network technicians to gain insight into RF activity in a specific spectrum or frequency range. Spectrum analyzers can either be hardware or software based and can be useful for identifying any potential interference before deploying a wireless network. see also RF Interference |
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Thin Cable Cable used to connect an access point to an antenna. Typically 0.1 inch in diameter. See also Low-Loss cable. |
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Universal Powerline Bus Protocol for data transmission over electrical circuits developed by Powerline Control Systems in California in 1999. |
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WEP encryption Specifies the level of encryption for WEP and can be 40,64, 128, or 152 bits. The higher the number of bits, the greater the security. The tradeoff is performance. Since 2003, WEP has not been a reliable way to secure a network. The standard has severe security compromises that were found by bona fide computer security researchers and hackers. |
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WiFi Jammer A device specifically designed to stop or interfere with WLAN communication within a certain area. These devices emit a white noise in frequencies 2400 -2483 Mhz. These exploit a feature of 802.11 called carrier sense multiple access (CSMA) which controls access to the air medium. With CSMA, client radios in devices take turns transmitting over a common RF channel. If another client radio is transmitting or a jamming signal is present, then all client signals within range will hold off from transmitting. This presents in a massive security hole for WiFi security devices such as IP cameras. |
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WiMax The wireless networking standard for wide area network connectivity set by the IEEE. Also known as 802.16, it specifies a system for fixed point to multipoint broadband access. This type of wireless network is commonly marketed as an alternative to wired broadband (ADSL) or cable broadband. |
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Wireless Controller The first commercial wireless controllers started to appear in 2002 from companies like AeroHive networks. They centralise the management of a wireless network. Instead of a network administrator visiting each access point individually for configuration a central wireless controller means the network can be managed from one location. Typical features which can be managed centrally include radio frequency management, QoS, security and roaming. |
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Wireless Distribution System ( also known as a Mesh Network) Traditionally wireless access points were linked to each other via a wired system. With WDS, the access points are linked together using a wireless medium. WDS requires that all stations in the network share the same frequency and use the same security encryption. For WDS to work best, all access points should be from the same manufacturer. |
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Wireless LAN switch |
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WPA Wi-Fi Protect Access (WPA) is a successor to WEP that provides better security. If your access point supports WPA, you should enable it. |
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Two-Factor Authentication An approach to wireless network security which requires two or more authentication sources for the user to login successfully to the wireless network. |
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Passphrase Many devices prompt you for a passphrase and then use that passphrase to generate the keys used for WEP encryption. |
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Key(s) You either enter these keys manually or allow the device to create them from a specified passphrase. The key must be provided by each wireless client, so you must enter a key in the wireless interface properties on each client device or use a method such as the Windows XP Wireless Setup Wizard to specify the key automatically. |
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WiFi Protected Setup (WPS) A computing standard developed by WiFi Alliance in 2007 in order to make wireless access points and routers easier to setup by non-professional I.T. users. By simply pressing a button, usually located at the back of their device, users could setup WPA2 encryption with an 8-digit pin number. However, in 2011 security researcher Stefan Viehbock discovered that in most cases, the pin number issued by the device could be broken down into only 11,000 combinations codes which leaves WPS easy prey for brute force attacks. This prompted the US- Computer Emergency Readiness Team to issue a warning to computer users to keep WPS switched off. |
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Wireless Station Any device that implements the 802.11 standard is called a wireless station (STA). |
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X10 One of the first commercialised home signalling and control protocols developed by Pico Electronics (Scotland) in 1975. A precursor to Universal Powerline Bus protocol of powerline networking. |
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Yagi Antenna a.k.a a Beam or Directional Antenna. An antenna which transmits and receives wireless signals in a narrow focussed area in the same way as a torch emits light in focussed beam. This type of antenna can be very useful in venues with very high ceilings, for example, a large sports hall which only requires coverage in a certain area. Placing a Yagi antenna at mid-level from the sides or from behind the coverage area and positing the antenna with a downward tilt can provide focussed and better coverage. Yagi antennas are commonly used for wireless bridges linking two buildings. see also Omni Directional Antenna. |
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Zigbee Zigbee is based on the IEEE 802.15.4 standard. Due to the low power consumption and cost, it is likely Zigbee will be the market leader for low duty and low power applications. Market penetration of Zigbee is expected to be less than of Bluetooth given limited targeted applications. It commonly replaces cabling for security sensors, fire detection and automation systems in homes and buildings. |
