Glossary

ITU-Tu International Telecommunication Union Telecommunication Standardization Sector International body that develops worldwide standards for telecommunications technologies. The ITU-T carries out the functions of the former CCITT.

J1 u Japanese transmission standard

LAN u Local-Area Network High-speed, low-error data network covering a relatively small geographic area (up to a few thousand meters). LANs connect workstations, peripherals, terminals, and other devices in a single building or other geographically limited area. LAN standards specify cabling and signaling at the physical and data link layers of the OSI model. Ethernet, FDDI, and Token Ring are widely used LAN tech- nologies.

LANE u LAN Emulation Technology that allows an ATM network to function as a LAN backbone. The ATM network must provide multicast and broadcast support, address mapping (MAC Address-to-ATM), SVC management, and a usable packet format. LANE also defines Ethernet and Token Ring ELANs.

LAPB u Link Access Procedure, Balanced. Data link layer protocol in the X.25 protocol stack. LAPB is a bit-oriented protocol derived from HDLC.

LEC u LAN Emulation Client Entity in an end system that performs data forwarding, address resolution, and other control functions for a single ES within a single ELAN. An LEC also provides a standard LAN service interface to any higher-layer entity that interfaces to the LEC. Each LEC is identified by a unique ATM address, and is associated with one or more MAC Addresses reachable through that ATM address.

LECS u LAN Emulation Configuration Server Entity that assigns individual LANE clients to particular ELANs by directing them to the LES that corresponds to the ELAN. There is logically one LECS per administrative domain, and this serves all ELANs within that domain.

LED u Light Emitting Diode A semiconductor device used to provide visual indications, used in place of an incandescent light. Also a semiconductor device used to transmit light into a fiber.

LES u LAN Emulation Server Entity that implements the control function for a particular ELAN. There is only one logical LES per ELAN, and it is identified by a unique ATM address.

LMI u Local Management Interface Set of enhancements to the basic Frame Relay specification. LMI includes support for a keepalive mechanism, which verifies that data is flowing; a multicast mechanism, which provides the network server with its local DLCI and the multicast DLCI; global addressing, which gives DLCIs global rather than local significance in Frame Relay networks; and a status mechanism, which provides an on-going status report on the DLCIs known to the switch. Known as LMT in ANSI terminology.

MAC Address u Standardized data link layer address that is required for every port or device that connects to a LAN. Other devices in the network use these addresses to locate specific ports in the network and to create and update routing tables and data structures. MAC addresses are 6 bytes long and are controlled by the IEEE. Also known as a hardware address, MAC-layer address, and physical address.

MCC u Multichannel Communication Controller

MiniDIN u Miniature multi-pin connector.

MUX u Multiplexer Combines multiple signals for transmission over a single line. The signals are demul- tiplexed, or separated, at the receiving end

NT1 u Network Termination 1 A device that provides the interface between customer premises equipment and central office switching equipment.

NVRAM u Nonvolatile RAM RAM that retains its contents when a unit is powered off.

OC3 u Optical Carrier 3 Physical protocol defined for SONET optical signal transmissions. OC3 signal levels put STS frames onto multimode fiber-optic line at at 155.52 Mbps.

OSI u Open System Interconnection International standardization program created by ISO and ITU-Tto develop standards for data networking that facilitate multivendor equipment interoperability.

PCI u Peripheral Component Interconnect A high-performance multiplexed address and data bus. Supporting 32-bit with optional 64-bit data transfers, the PCI bus is intended to be an interconnect between peripheral controllers, peripheral add-in boards, and processor/memory systems. The PCI bus operates at up to 33 MHz, providing burst transfer rates up to 132 MBps 32 bits wide, or up to 264 MBps 64 bits wide.

PDN u Public Data Network Network operated either by a government (as in Europe) or by a private concern to provide computer communications to the public, usually for a fee. PDNs enable small organizations to create a WAN without all the equipment costs of long-distance circuits.

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