rand names. MWS (Multimedia Wireless System) A European term for high-frequency BFWA that focused on broadband services, including real-time video, streaming video, and video transfer. NACK or NAK (negative acknowledgment) A message that indicates an error in trans- mission and says the previous block needs to be resent before anything else can happen. NADC (North American Digital Cellular) A TIA standard that uses TDMA and TDD schemes and offers a total of three time slots. NADC operates on the 800MHz frequency band, uses AMPS for signaling to reserve resources, and transfers speech in digital form; therefore, it is a digital overlay that is interoperable with analog AMPS infrastructure. nailed-up connection A slang term for a permanent, dedicated path through a switch. A nailed-up connection is often used for lengthy, regular data transmission going through a PBX. name resolution The process of mapping a name to a corresponding address. DNS provides a mechanism for naming computers in which programs use remote name servers to resolve machine names into IP addresses for those machines. nanosecond One-billionth of a second. (network access point) The point at which backbones interconnect to exchange traf- fic between providers. Bottlenecks at NAPs greatly affect the ability to roll out new time-sensitive, loss-sensitive applications, such as Internet telephony, VoIP, VPNs, streaming media, and TV over Internet. narrowband A service occupying low bandwidth (64Kbps or below). narrowcast Transmission of specific programming to predetermined users of a telecommunica- tions network. With narrowcast, only some users of the network are receiving the same information. NAS (network attached storage) Storage devices that can be accessed over a computer network rather than being directly connected to the computer. This enables multiple computers to share the same storage space, which minimizes overhead. NAT (Network Address Translation) An Internet standard that enables a LAN to use one set of IP addresses for internal traf