H OTS POT GATEWAYGlossary of Terms 327Glossary of Terms802.11xRefers to a family of specifications developed by the IEEE for wireless LAN technology. 802.11 specifiesan over-the-air interface between a wireless client and a base station, or between two wireless clients. TheIEEE accepted the specification in 1997. There are several specifications in the 802.11 family:802.11Applies to wireless LANs and provides 1 or 2 Mbps transmission in the 2.4 GHz band using eitherFrequency Hopping Spread Spectrum (FHSS) or Direct Sequence Spread Spectrum (DSSS).802.11aAn extension to 802.11 that applies to wireless LANs and provides up to 54 Mbps in the 5GHz band.802.11a uses an Orthogonal Frequency Division Multiplexing (OFDM) encoding scheme rather thanFHSS or DSSS.802.11b(also referred to as 802.11 High Rate or Wi-Fi™) An extension to 802.11 that applies to wireless LANsand provides 11 Mbps transmission (with a fallback to 5.5, 2 and 1 Mbps) in the 2.4 GHz band. 802.11buses only DSSS. 802.11b was a 1999 ratification to the original 802.11 standard, allowing wirelessfunctionality comparable to Ethernet.802.11gApplies to wireless LANs and provides 20+ Mbps in the 2.4 GHz band.802.1QAn IEEE standard for providing a virtual LAN capability within a campus network. 802.1Q establishes astandard format for frame tagging (Layer 2 VLAN markings), enabling the creation of VLANs that useequipment from multiple vendors.10/100 EthernetSee Ethernet.AAA(Authentication, Authorization, and Accounting) A combination of commands used by Nomadix Gatewaysto authenticate, authorize, and subsequently bill subscribers for their use of the customer’s network. Whena subscriber logs into the system, their unique MAC address is placed into an authorization table. Thesystem then authenticates the subscriber’s MAC address and billing information before allowing them toaccess the Internet and make online purchases. See also, MAC Address.Access ConcentratorA type of multiplexor that combines multiple channels onto a single transmission medium in such a waythat all the individual channels can be simultaneously active. For example, ISPs use concentrators tocombine their dial-up modem connections onto faster T-1 lines that connect to the Internet. Concentratorsare also used in Local Area Networks (LANs) to combine transmissions from a cluster of nodes. In thiscase, the concentrator is often called a hub.
