Wide Band (UWB): Ultra Wide Band is defined as any transmis- sion in which the 3 dB bandwidth is 20% or more of the centre frequency, with a minimum bandwidth of 500 MHz. In the USA, the FCC defines a UWB passband from 3.1 to 10.6 GHz in which maximum transmitter power must be below -41.3 dBm/MHz. This power level is less than that permitted for unintentional emitters such as computers and other electronic devices. Voice over Internet Protocol (VoIP): Voice over Internet Protocol refers to the transmission of voice data over the Internet using the UDP transport protocol. Virtual LAN (VLAN): A virtual LAN is a subset of client stations in a LAN or WLAN that is defined using software in order to be able to isolate traffic in the VLAN from the wider LAN. For example this may be because traffic in the VLAN is more susceptible to attack (e.g. VoIP phones) and needs to be treated as "untrusted" to assure the security of the rest of the LAN. Virtual Private Network (VPN): A Virtual Private Network is formed when a remote device connects to a private network via a public network such as the Internet. A tunnelling protocol such as IPSec, L2TP or PPTP ensures privacy by encrypting data transferred over the public network. Wired Equivalent Privacy (WEP): A security feature of the 802.11 stan- dard that was intended to provide security equivalent to that of a wired LAN. Chapter Sixteen Encryption vulnerabilities led to WEP being superseded by WPA and by 802.11i security mechanisms. Wireless Ethernet Compatibility Alliance (WECA): Original industry sponsors of the Wi-Fi standard, now re-branded as the Wi-Fi Alliance. The Wi-Fi logo gives a guarantee of interoperability of 802.11 based wireless networking devices. Wi-Fi Protected Access (WPA): An enhanced version of IEEE 802.11 security, developed by the Wi-Fi Alliance as a precursor to the IEEE 802.11i standard, which provides stronger encryption and manages the dis- tribution of encryption keys. WPA also provides user authentication and message integrity checking (MICHAEL). 