RAD - D

Data - Information represented, in digital form, including voice, text, facsimile and video.

dB (Decibel) - A unit used to measure relative increase or decrease in power, voltage or current, using a logarithmic scale.

dBm - A measure of power in communications: the decibel in reference to one milliwatt (0 dBm = 1 milliwatt and -30 dBm = .001 milliwatt).

DS0 (Digital Subscriber Level Zero) - A 64 kbps unit of transmission bandwidth. A worldwide standard speed for digitizing one voice conversation, and more recently, for data transmission. Twenty-four DS0s (24 x 64 kbps) equal one DS1.

DS1 (Digital Signal Level 1) Channel - Framing specification used in transmitting digital signals at 1.544 Mbps on a T1 facility or 2.048 Mbps on an E1 facility.

DS2 Channel - For a T1 line, a 6.312 Mbps channel that consists of four DS1 channels; for an E1 line, an 8.45 Mbps channel that consists of four DS1 channels.

DS3 Channel - A 44.736 Mbps line consisting of seven DS2 channels. A DS3 line is also called a T3 line.

DSL (Digital Subscriber Line) - A modem technology for transmitting information at high speeds on existing copper phone lines to homes and businesses. DSL operates over existing copper telephone lines and requires runs of usually less than 20,000 feet to a central telephone office. Types of DSL include asymmetric DSL (ADSL), symmetric DSL (SDSL), high-bitrate DSL (HDSL) and the latest, symmetric high-bitrate DSL (SHDSL).

E1 - A 2.048 Mbps line, common in Europe, that supports thirty-two 64 kbps channels, each of which can transmit and receive data or digitized voice. The line uses framing and signaling to achieve synchronous and reliable transmission. The most common configurations for E1 lines are E1 PRI, and unchannelized E1.

E1 MLPPP (Multilink Point-to-Point Protocol) - Combining (bonding) multiple PPP (Point-to-Point Protocol) links between two systems into one logical data pipe. MLPPP is a standard IETF protocol.

E3 - The European standard for high speed digital transmission, operating at 34 Mbps.

Echo Cancellation - Echo cancellation improves the quality of voice transmissions. It eliminates the echo that results from the reflection of the telephony signal back to the caller, which can occur in a 4-wire to 2-wire hybrid connection between the VFRAD and the telephones or PBX. The longer it takes the signals to return to the caller, the more perceptible the echo.

Echo-Signal - Distortion occurring when a transmitted signal is echoed back (reflected) to the originating station.

EFM Ethernet in the First Mile (also known as IEEE 802.3ah) - A collection of protocols specified in IEEE 802.3, defining Ethernet in the access networks, i.e. First/Last Mile. EFM also addresses other issues required for mass deployment of Ethernet services, such as operations, administration and maintenance (OAM) and compatibility with existing technologies (e.g. spectral compatibility for copper).

Encapsulation - Encapsulating data is a technique used by layered protocols in which a low level protocol accepts a message from a higher level protocol, then places it in the data portion of the lower-level frame. The logistics of encapsulation require that packets traveling over a physical network contain a sequence of headers.

Ethernet - Most popular local area network (LAN) technology in use today. All stations on the LAN share the total bandwidth, which is at speeds of 10 Mbps (Ethernet), 100 Mbps (Fast Ethernet), or 1000 Mbps (Gigabit Ethernet).

Ethernet OAM - Ethernet OAM (Operation, Administration and Maintenance) is a set of functions designed to monitor network operation in order to detect network faults and measure its performance. Carrier-class Ethernet services require automated end-to-end management and monitoring, including OAM capabilities such as connectivity verification, fault detection, performance monitoring, and alarm indication.

Ethernet over SDH or SONET - Although SDH and SONET networks were originally engineered to transport voice traffic, many carriers are using their ubiquitous SDH and SONET infrastructure to deploy Ethernet services. Recent developments in Next Generation SDH/SONET have made these networks more cost-effective and "user friendly" for Ethernet traffic.

FCC (Federal Communications Commission) - The regulatory agency established in the United States for all interstate radio and electronic communications.

Frame - A logical grouping of information sent as a link layer unit over a transmission medium. The terms packet, datagram, segment and message are also used to describe logical information groupings.

Full Duplex - A circuit or device permitting transmission in two directions (sending and receiving) at the same time.