ission. Its frequencies are approximately in the 20GHz to 30GHz range. Kbps (kilobits per second) 1,000 bits per second. KHz (kilohertz) 1,000 cycles per second. Ku-band The portion of the electromagnetic spectrum that is being used increasingly for sat- ellite communications. Frequencies are approximately in the 12GHz to 14GHz range. (Layer 2 Tunneling Protocol) A Layer 2 protocol that can work in a non-IP enter- prise environment. L2TP is used primarily by service providers to encapsulate and carry VPN traffic through their backbones. LAN (local area network) (1) A system for linking terminals, programs, storage, and graphic devices at multiple workstations over relatively small geographic areas. (2) A network that is limited to a small area, such as the premises of an office building or plant. LANE (LAN Emulation) An ATM Forum standard for emulating a LAN across an ATM network. LAPB (Link Access Protocol Balanced) A modified form of HDLC that the ITU-T chose as the link-level protocol for X.25 networks. LAPB provides for the reliable transfer of a packet from a host to an X.25 packet switch, which then forwards the packet to its destination. LAPD (Link Access Protocol on the D Channel) An ISDN data link layer protocol the D channel. LAPD was derived from the LAPB protocol, designed primarily to satisfy the sig- naling requirements of ISDN basic access. laser (light amplification by simulated emission of radiation) A device that con- verts electrical energy into radiant energy in the visible or infrared parts of the spectrum, emit- ting light with a small spectral bandwidth. Lasers are widely used in fiber-optic communications, particularly as sources for long-haul links. LATA (Local Access and Transport Area) Geographic regions within the United States that define areas within which the RBOCs can offer exchange and exchange access services (local calling, private lines, and so on). latency The delay associated with the time it takes a packet to travel from entry point to exit point. layer In the OSI reference 