A

Ad Hoc Mode - This refers to a WLAN scenario in which there is no access point. All devices communicate directly with each other in peer-to-peer mode. This is called an Independent Basic Service Set (IBSS).

Ad Hoc Network - This type of network is used for small environments with two to four PCs and a couple of shared printers, at most. An ad hoc WLAN does not require an access point.

Ad Hoc WLAN - This refers to a client-to-client WLAN configuration.

Access Point - An access point is a Layer 2 device that provides connectivity to a network for individual wireless devices.

Access Point Filters - These settings are used to prevent certain PCs on a network from accessing the Internet.

Accounting Management - This is the process of collecting, interpreting and reporting costing and charging related information about network resource usage.

Adjacent Channels Interference - Interference from the channels immediately above or below the current frequency.

All-Band Interference - Interference that occurs when a source interferes with the entire RF band that is being used.

Antenna Beamwidth - This refers to the narrow or broad focus of radio waves from an antenna signal.

Antenna Gain - This is the ratio of a signal that is received or transmitted by a given antenna. Antenna gain can only be achieved by making an antenna directional. It is usually expressed in dB.

Antenna Mode - Most wireless client adapters have a diversity antenna and will use the antenna with the stronger signal on a packet-by-packet basis. Some client software will let you select which one to use.

Antenna Polarization - This is the physical orientation of an antenna in relation to the Earth’s surface. Vertical polarization is perpendicular to the Earth’s surface. A horizontally-polarized antenna is parallel to the surface of the Earth.

Authentication - The process of identifying an individual, which is usually based on a username and password.

Authenticated and Unassociated - After a radio has been authenticated and before association with an AP and SSID, a client will be in this transitional state. The client is only in this state for a few milliseconds.

Authenticated and Associated - This is the final state, which a client will remain in until it shuts down, roams to a different cell, or loses the signal. The client can send and receive data through the access point in this state.

Authorization - The process of giving individuals access to system objects based on their identity.

B

Basic Service Set (BSS) - This refers to a wireless topology in which a single access point exists.

Broadcast Address - For both MAC and IP addresses, if the destination is all IP hosts on the subnet, the address is a broadcast address.

Beacon - This is short for a beacon management frame, which is a short frame that is sent periodically to organize and synchronize communications on a WLAN.

Bit Error Rate (BER) - A ratio of errors to good packets.

Bridge Mode - An AP operating in bridge mode essentially becomes a wireless bridge. Bridges are used to link together two or more wired segments, which may be located in different parts of the same building or in separate buildings.

BSS and PSP Mode - Stations will send a frame to the AP, telling it that they are going to sleep. The AP keeps track of which stations are sleeping and will buffer any frames for these devices.

C

Carrier Sense Multiple Access with Collision Detection (CSMA/CD) - This is the Ethernet media access method. All network devices contend equally for access to transmit. If a device detects the signal of another device while it is transmitting, it aborts transmission and retries after a brief pause.

Clear Channel Assessment - There are different options for a client to check and decide that a medium is idle and it can transmit. Available options depend on the client hardware and software in use.

Client Adapter - A client adapter is a Layer 2 device that provides connectivity to an individual device.

Co-channel Interference - A situation in which multiple WLANs in a building all use the same channel. These separate WLANs may interfere with each other.

Co-location - The concept of using multiple access points on a WLAN to provide more bandwidth to an area of coverage.

Configuration Management - Controlling physical, electrical, and logical inventories. Configuration documentation is useful for long-range planning, as well as during troubleshooting.

Compact Flash (CF) Card - CF Cards are smaller than PC Cards and use less power. They are typically used in PDAs. Installation and configuration vary based on the devices.

Control Frames - These are the highest priority frames. They are used for functions that either help set up a WLAN for data transmission or acknowledge it.

Counter-Mode/CBC-MAC Protocol (CCMP) - CCMP is based on the Advanced Encryption Standard (AES) instead of RC4 and is considered un-crackable by most cryptographers. AES uses something called the Rijandael algorithm with 128-bit, 192-bit, and 256-bit keys.

D

Data Frames - All protocols exist to reliably transmit and receive data frames. Some contention-free functions also use data frames.

Demilitarized Zone (DMZ Host) - This is a computer or small subnetwork that sits between a trusted internal network, such as a corporate private LAN, and an untrusted external network, such as the Internet.

Detachable Antenna - A detachable antenna provides flexibility to select the best antenna for the location and usage of an AP.

Direct Sequence - Direct sequence is the most widely used spread spectrum type, probably because it is easier to implement and provides data rates as high as 11 Mbps, versus the 2 Mbps of FHSS.

Direct Sequence Spread Spectrum (DSSS or DS) - DSSS is a technique in which a pseudo-random sequence directly phase modulates a carrier signal. The data has already been modulated onto the carrier. The resulting RF signal uses a noise-like spectrum and can intentionally be made to look like noise, to all but the intended radio receiver.

Distributed Control Function IFS (DIFS) - If no control messages are sent and the PCF time has passed, this timer will be the next to expire. At this point, each station will start the timer for its random backoff period. DIFS is 50 microseconds long, which is PIFS plus one slot time.

Domain Name System/Service (DNS) Server - A DNS server is a distributed database that enables a user to type a name such as www.linksys.com to access a Web page, even though the routers that will forward the user’s request use IP addresses.

Downfade - A situation that occurs when reflected radio waves, if out-of-phase with a primary signal, result in decreased signal amplitude at the receiver.

Drop the Frame - This occurs when a destination MAC address is on the same port as the one through which a frame enters.

DSSS-Specific Information - For DSSS systems, a beacon will indicate the channel that is in use, which is Channel 6 by default.

Dwell Times - The FCC defines the maximum dwell time as 400 ms per carrier frequency in any 30-second time period.

Dynamic Host Configuration Protocol (DCHP) Server - DHCP will automatically assign an IP address and other settings to a device, such as the DNS servers to use and the default gateway IP address to use.

Dynamic Rate Shifting (DRS) - DRS automatically adjusts a data rate to compensate for a decrease in signal strength or signal quality.

E

EAP-Cisco Wireless or Lightweight Extensible Authentication Protocol (LEAP) - This is used primarily with Cisco Aironet access points. LEAP provides security during login, encrypts data with automatically generated dynamic WEP keys, and uses two-way authentication. It is based on a strong challenge-password exchange, rather than certificates.

EAP-Message Digest-5 (EAP-MD-5) Challenge - This is the first EAP type, which uses the Message Digest-5 encryption algorithm. It works like CHAP (Challenge Handshake Protocol), but on a wireless LAN.

EAP-Transport Layer Security (EAP-TLS) - This uses certificate-based, mutual authentication for the client and the network. Both client-side and server-side configuration is needed, which makes this a high-maintenance option.

EAP-Tunneled Transport Layer Security (EAP-TTLS) - This is an extension of EAP-TLS. It provides the same functions, but without the need for client configuration of the certificate.

Encapsulation - Encapsulation, or tunneling, is a technology that enables one network to send its data through the connections of another network. Tunneling works by encapsulating a network protocol within packets carried by the second network.

Equivalent Isotropic Radiated Power (EIRP) - EIRP is the power radiated by an antenna, which takes into account the gain provided by the antenna.

Ethernet and Serial Converters - These convert either an Ethernet or a serial port to a PCMCIA slot, into which a PC card radio is inserted. For configuration, there is typically console access through a 9-pin serial port and client utilities. These are most often used on older equipment. No special drivers are needed for the Ethernet or serial interface.

Ethernet Switch - A LAN switch is a Layer 2 device that provides connectivity to a network for individual Ethernet devices.

Extended IFS (EIFS) - This is a variable length space that is longer than DIFS. EIFS is used after a frame transmission results in corrupted data and is not acknowledged.

Extended Service Set (ESS) - This refers to a wireless topology in which more than one access point is connected to a wired segment.

F

Fault Management - Includes all activities, procedures, and tools required to dynamically deal with problems that arise. The objective is to maintain high availability of network services.

Federal Communications Commission (FCC) - This organization defines and enforces the laws governing wireless communications.

FHSS-Specific Information - If FHSS is used on a WLAN, a beacon will contain parameters such as the hop and dwell time and the hop sequence to use.

Filtering - MAC address or protocol filtering can provide a basic level of security by screening out devices that are not in a defined MAC or protocol filter list.

Forward the Frame - A bridge will only send a frame to the segment that contains the destination MAC address.

Frequency - This is the number of times each second that a signal completes a cycle, or switches from positive to negative and back.

Frequency Bands - 2.4000 GHz to 2.4835 GHz. There are 79 possible carrier frequencies in this range.

Fragment Threshold - This is the maximum size of a packet that is not fragmented. Larger packets are broken down into multiple smaller packets.

Full-Duplex - Data transmission in a full-duplex network can go in both directions at the same time.

G

H

Half-Duplex - Data transmission in a half-duplex network can only go in one direction at a time.

Hidden Node - A problem that occurs when certain nodes are unable to detect when certain other nodes transmit.

Hop Sequences - 802.11 specifies that at least 75 of the 79 possible carrier frequencies must be used in a frequency hop set and that at least 6 MHz must separate successive hops.

Hot Spot - This is a public or private location with an 802.11 access point and a connection to the Internet.

HP Digital Media Receiver - The HP Digital Media Receiver allows users to enjoy digital music and photos from a PC, using the best stereo system and TV in a home.

Hub - A hub is common connection point for devices in a network. Hubs are commonly used to connect segments of a LAN. A hub contains multiple ports. When a packet arrives at one port, it is copied to the other ports so that all segments of the LAN can see all packets.

I

IBSS and PSP mode - Since there is no AP in an ad hoc network, each device must buffer any packets it has to send to another wireless client. Clients take turns sending beacons, using a manufacturer-dependent method. This typically includes a randomization factor, to share this responsibility fairly.

Infrastructure Mode - This refers to a WLAN scenario in which there are one or more access points. All devices communicate with each other through an access point. If there is one access point, the WLAN is called a Basic Service Set (BSS). If there are multiple access points, it is called an Extended Service Set (ESS).

Infrastructure WLAN - This refers to a client-to-access point WLAN configuration.

IP Network Address - A network address uniquely identifies a given device anywhere within the entire internetwork. Parts of the IP address identify the network, the subnet, and the host.

Institute of Electrical and Electronics Engineers (IEEE) - This organization creates the standards that allow wireless devices to interoperate.

Interact TV and Telly - Interact-TV serves digital media from a Telly MC1000 Home Entertainment Server. The Home Media Server lets users access files from anywhere on a network. Telly has built-in controls that can be accessed through a Web browser and managed from a PC. Telly can easily manage, access, and play back digital media on a TV, no matter where files are on a network.

J

Jamming Attack - Similar to a Denial of Service (DoS) attack, in that it prevents valid users from accessing a WLAN. A jam is an overwhelming RF signal, which can be produced by a high-power RF signal generator.

K

L

Launch Effect - This refers to the scenario which occurs at the series of wavelengths at each frequency, for which it becomes very easy for energy to escape from the transmission line and become radio waves.

Line of Sight (LOS) - LOS is simply the apparently straight line from an object being sighted, or the transmitter, to the eye of the observer, or the receiver.

Link Status Monitor - This will display packet errors, bytes/packets transmitted and received, link viability, and more.

Local Area Network (LAN) - This is a computer network that spans a relatively small area. Most LANs are confined to one building or group of buildings. Most LANs connect workstations and PCs.

Linksys Wireless-B Adapter - This device connects to a TV or stereo and lets users listen to and view digital music and photos. It wirelessly connects to a PC to access the music and photos.

M

MAC and Protocol Filtering - Filtering at the data-link layer helps block unauthorized users who are not in the MAC filter list. Protocol filtering can be used to determine which protocols can use the WLAN, such as HTTP for Internet traffic or SMTP for e-mail.

Man-in-the-Middle Attacks - Used to intercept data to and from clients.

Management Frames - These are used for setting up connections.

Modular Radio Cards - With a single PCMCIA slot, this option allows users to upgrade by swapping the radio card. With multiple slots, an access point could perform both the AP function and the bridging function.

Motorola Simplefi Wireless Digital Audio Receiver - This allows users to stream audio from a PC or the Internet through a broadband connection directly to a home stereo.

Multicast Address - For both MAC and IP addresses, if the destination is some subset of all of the IP hosts, the address is a multicast address. Multicast addresses are also called group addresses.

Multipath - The combination of a primary signal plus duplicate or echoed radio waves that are caused by reflections of RF signals off objects located between a transmitter and a receiver, such as a body of water

N

Narrowband Interference - A disruption in only a portion of the RF band.

Near/Far - A problem caused when nodes nearer to an access point use higher power and the nodes that are further away use lower power. The lower-power nodes cannot be heard over the louder traffic of the nearer nodes.

Network Address Translation (NAT) Server - A NAT server will translate all of the requests from a private IP address to a non-private IP address for transmission on the Internet. When a response is received, the address will be translated back to the private IP address.

Network Protocol Analyzer - This can be used to capture any packets that are transmitted on nearby wireless LANS. It can also show users which channels are being used, the data rates, signal strengths, and more.

Nulling - A situation that occurs when the out-of-phase arrival of a reflected wave completely cancels the amplitude of a primary wave.

O

Omni-directional Antennas - This type of antenna radiates energy equally in all directions, but not along the length of the antenna.

Onkyo Net-Tune Products - Net-Tunes can be used to stream music to multiple users on a network. Up to 12 users in different locations can access tracks from the same album at the same time. CDs and external sources can be recorded onto a hard drive in MP3 (compressed) and PCM (uncompressed) formats. Users can also stream Internet radio broadcasts from around the globe.

Open System Authentication - For this type of authentication, a client only needs the correct SSID to connect.

Orthogonal Frequency-Division Multiplexing (OFDM) - OFDM is specified for both 802.11a, which operates in the UNII 5-GHz band, and for 802.11g, which operates in the 2.4-GHz band, for backwards compatibility.

Oscillation - This is when energy transfers from one field to the other and back.

OSI Reference Model - The OSI reference model is used to describe networking functionality. It splits the entire process of delivering data into smaller chunks of functionality. The seven-layer OSI model also creates a hierarchy of functionality, in which the lower layers must be functioning properly in order for higher layers to operate.

P

PCMCIA (PC) Card - PC Card radios support plug-n-play. They are used directly in both laptops and PDAs. There is usually a client utility for installing the driver and configuring the wireless parameters.

Performance Management - Performance management is proactive. It requires continuous evaluation of defined performance indicators for network operation.

Physical Address - On a LAN, every device has a unique identifier that is called many things, including physical address, node address, data-link address, MAC address, and burned-in address (BIA). This address is local to the directly-connected environment.

Pocket PC - This is used to describe the earlier Windows CE and the later Pocket PC operating systems from Microsoft.

Point Coordination Function (PCF) - This is an access method that provides a contention-free mode of operation. This is also called deterministic access. Deterministic access to a shared medium is important for functions that require a known latency, such as voice over IP (VoIP) applications.

Point Control Function IFS (PIFS) - Only an AP can transmit after the PIFS interval has passed. When the deterministic polling access method is used, this will give the AP priority over client stations that want to transmit. PIFS lasts for 30 microseconds, which is SIFS plus one slot time.

Power and Speed Monitoring Tools - These utilities display the current data rate and the power level, which is helpful in mapping out coverage areas.

Power over Ethernet - This feature allows access point to be placed anywhere within 100 m of a wired LAN, with no need for electrical outlets.

Print Server - A print server is a computer or stand-alone device that manages one or more printers. It connects a printer to a network and allows users to share the printer.

Protected EAP (PEAP) - This was jointly developed by Cisco Systems and Microsoft. It provides the same functions as TTLS and Windows XP supports it natively.

PSTN - This is a general term that is used to describe the public switched telephone network, which is an international telephone system based on copper wires carrying analog voice data.

Q

QCast Software - This allows existing entertainment devices, such as a Sony PlayStation, to be a digital media player. The device can wirelessly receive images and streaming video and audio from a host computer locally or from the Internet.

R

Radome - A domelike shell or cylinder in which an antenna may need to be housed in if certain weather conditions such as ice or heavy rain occur frequently.

Refraction - Refraction is the bending of radio waves as they pass through a medium of a different density, such as going through the air, and then through glass. When this happens, some of the wave will be reflected away from the desired signal path and some will be bent as it passes through the medium.

Repeater Mode - In repeater mode, an AP provides a wireless upshot link into a wired network. The AP repeater connects to clients as an access point. It connects to a root mode AP as a client.

RF Amplifier - This device increases the amplitude of a signal.

RF Attenuator - This is the opposite of an RF amplifier and causes a measurable loss in an RF signal.

RF Splitter - An RF splitter has one input connector and multiple output connectors. It splits an incoming signal into multiple, lower-power signals.

Root Mode - This is the default mode of operation. In root mode, the AP is connected to the wired foundation of a network, usually the Ethernet.

Router - A device that forwards data packets along networks. A router is connected to at least two networks, commonly two LANs or WANs or a LAN and its ISP’s network. Routers are located at gateways, the places where two or more networks connect.

S

Scanning - This is the process a WLAN client uses to look for networks to which the device can connect.

Security Management - This is the set of functions that ensure the ongoing protection of a network and all of its key components. This includes backups, physically locking up the server, and the use of passwords.

Semi-directional Antennas - These antennas direct significantly more energy in one direction, not in a circular pattern like omni-directional antennas.

Service Set Identifier (SSID) - The SSID, which is also called the Extended SSID (ESSID), is a unique, case-sensitive alphanumeric string that is 2 to 32 characters long. It is used as the WLAN network name and can be used to segment a network. It also acts as a weak security measure when clients attempt to join a WLAN.

Shared Key Authentication - This method uses WEP during the authentication phase. To use this type of authentication, the keys must be configured on the AP and on all clients that will connect to it.

Short Interframe Space (SIFS) - This is the shortest space. It is used for the highest-priority functions, such as sending ACK frames. SIFS has a duration of 10 microseconds.

Site Survey - The purpose of a site survey is to make sure that wireless LAN users have a continuously strong signal, no matter where they roam within planned coverage areas.

Small Office/Home Office (SOHO) Network - This term refers to a small or home office network environment, which may include a small number of centralized servers or in some cases no centralized servers.

Spectrum Analyzer - This locates sources of RF interference such as other WLANs. This tool will scan the entire 2.4-GHz or 5-GHz range and graphically display the results, which show RF sources and other potential sources of interference.

Subscriber Identification Module (SIM) - This technology is an authentication tool for WLAN hot spots. SIM card-based smart cards can be used to identify wireless users connecting to the Internet.

Super Access Point - This is an access point that has much longer range and can take the place of several regular APs. One super access point might serve an entire floor.

Switch - A switch is a device that filters and forwards packets between LAN segments.

T

Temporal Key Integrity Protocol (TKIP) - TKIP is based on RC4 encryption. It is implemented in a way that addresses the weaknesses of WEP. For example, it generates new encryption keys for every 10 KB of data transmitted, as opposed to the static keys of WEP.

Throughput - The amount of data transferred from one place to another or processed in a specified amount of time.

The Wireless Fidelity (Wi-Fi) Alliance - This organization provides interoperability testing and certification.

Time Synchronization Information - This is a time stamp contained in a beacon. All associated stations will use it to set their clocks. It also includes the interval at which beacons will be sent, so clients know when to expect the next one.

TiVo - This is a paid service that automatically records specified shows when they air, even if the timeslot changes. Users can watch what they want, when they want. TiVo is also a digital video recorder (DVR).

Traffic Indication Map (TIM) - When clients put their radios in power-save mode, they are said to be sleeping. A sleeping station will power up its receiver when the next beacon is expected. It will then check the TIM in the beacon to see if the AP has frames addressed to it that are waiting to be sent. If so, the station will remain awake to receive the frames. If not, it will return to power-save mode.

Transmission Control Protocol (TCP) - TCP is one of the main protocols in TCP/IP networks. Whereas the IP protocol deals only with packets, TCP enables two hosts to establish a connection and exchange streams of data. TCP guarantees delivery of data and that packets will be delivered in the same order in which they were sent.

Transmit Power - For adapters that have variable output power, this parameter lets you adjust the power to be used. This is typically only used during a site survey.

U

Unauthenticated and Unassociated - This is the initial state of a wireless station. It is also the state of a client that has failed authentication. A client cannot send or receive data in this state.

Unicast Address - For both MAC and IP addresses, if the destination is a single IP host, the address is a unicast address.

Universal Wireless Multimedia Receiver - This is a Wireless device that plays audio, including Internet radio, and streams video.

Universal Wireless Broadband Router - This connects a local network to the cable or DSL modem and to the Internet. It provides the usual router functions.

Upfade - A situation that occurs when an in-phase reflected signal adds to the strength of a primary signal.

V

Variable Output Power - This option allows an administrator to control the power. Increasing the power allows clients to move further away and still remain connected. Lowering the power can improve security, by limiting the size of the cells.

Virtual Private Network (VPN) - A way to communicate through a dedicated server securely to a corporate network over the internet. VPNs are also recommended to secure 802.11b wireless LANs as well.

W

WAN Port - This is the Internet interface to an Ethernet port that is connected to the service provider equipment, such as a cable or DSL modem or a dial-up modem.

War Driving - When a hacker moves around a city, using a Wi-Fi ready PC, searching for unprotected wireless networks.

Wide-Area Network (WAN) - A WAN is a computer network that spans a relatively large geographical area. It typically consists of two or more local-area networks (LANs). Computers connected to a wide-area network are often connected through public networks, such as the telephone system. They can also be connected through leased lines or satellites. The largest WAN in existence is the Internet.

Wi-Fi - This term is used generically in reference to an 802.11 network. Any products that are tested and approved as Wi-Fi Certified by the Wi-Fi Alliance are interoperable with each other, even if they are from different manufacturers. A user with a Wi-Fi Certified access point can use any brand of brand of client hardware that also is certified.

Wired Equivalent Privacy (WEP) - The method of encryption specified by 802.11. This is a simple algorithm that uses a pseudo-random number generator (PRNG) and a RC4 stream cipher, which encrypts and decrypts data quickly.

Wireless Access Point - An access point connects users to other users within the network and also can serve as the point of interconnection between the WLAN and a fixed wire network.

Wireless Gateway - This device functions as several devices in one box. It performs router (Layer 3) functions, access point (Layer 2) functions, Ethernet switch (Layer 2) functions, DHCP, NAT, and/or DNS Server functions.

Wireless Gateway - This all-in-one device includes a router, an Ethernet switch, and an access point, in one device.

Wireless USB Adapters - USB client devices support plug-n-play. They are used on any device with a USB port.

Workgroup Bridges (WGBs) - A WGB groups multiple WLAN client devices and bridges them to an access point. On the AP, the clients all appear as a single WLAN client device.

World Mode - Some high-end adapters can automatically adjust the channels that are used, based on the country.

X

Y

Yamaha MusicCAST - This device allows users to listen to what they want, when they want, at the touch of a button. Users can store music collections in one central location, create play lists and custom CDs, preserve vintage vinyl records as digital files, and then transmit them anywhere in a home wirelessly.

Z