4 Electronic Switching System :
Class 4 stored, program controlled central office switch made by Lucent.

5ESS 5 Electronic Switching System :
A digital central office manufactured by Lucent.

AAL2 (ATM Adaptation Layer 2) :
A standardized protocol used for carrying time-dependant audio or video traffic over an ATM.

Access Tandem :
A Local Exchange Carrier (LEC) switching system that provides a concentration and distribution function for originating and/or terminating traffic between a LEC end office network and IXC POPs.

ADSL (Asymmetric Digital Subscriber Line) :
A technology for transmitting digital information at high bandwidths on existing phone lines to homes and businesses. Unlike regular dialup phone service, ADSL provides continuously available, "always on" connection.

Advanced Intelligent Network (AIN) :
An evolving, service-independent architecture that allows a carrier to quickly and economically create and modify telecommunication services for its customers.

A-Link :
A signalling link in the Signalling System 7 (SS7) world that connects a signal transfer point (STP) to a service switching point (SSP) or service control point (SCP). A-links operate at a transmission speed of 56 Kbps.

Analog System :
The simple way to transmit speech. The first networks for mobile phones were analog. Analog systems include AMPS, NMT, and ETACS.

ARP (Address Resolution Protocol) :
A protocol used to query IP hosts about their physical (L2) addresses. If ARP is unavailable, the IP addresses must be manually mapped to their L2 addresses by the network administrator.

AS (Application Server) :
A server program in a computer in a distributed network that provides the business logic for an application program.

Asynchronous :
A type of transmission in which each character is transmitted independently without reference to a standard clock. It can also mean that there are different capacities for data transfer in each direction, for example the old 90/200 baud modems and the new ADSL.

Asynchronous Mode :
A standard for data transmission where each data package has a start and stop bit. See also Synchronous Mode.

ATM (Asynchronous Transfer Mode) :
A high speed switching system that uses 53-byte size cells to transmit voice, data and video. A cell in analogous to envelopes that each carry the same number of bits.

Bandwidth :
The capacity in a network for data transmission. Bandwidth is measured in the number of data bits that can be handled per second (bps, Kbps, Mbps or Gbps).

BICC (Barrier Independent Call Control) :
A standard that focuses on switch-to-switch communication to enable communication between VoPacket nodes and allow the termination of a TDM call without using SIP. BICC is favored by larger carriers such as AT&T.

B-ISDN (Broadband Integrated Services Digital Network) :
An evolving standard for the second generation of integrated services digital networks. Broadband ISDN services employ packet switching to integrate voice and data services over a high-speed, packet-based infrastructure.

Bit :
The smallest unit of data in a computer. A bit has a single binary value, either 0 or 1.

BPS (bits per second) :
Data transmission speed, the number of pieces of information transmitted per second.

BRI (Basic Rate Interface) :
The ISDN interface standard for single-line ISDN service. This standard provides for two message-bearing 64 Kbps B channels for speech and data, plus a 16 Kbps D channel for network signaling and data.

Broadband Technology :
The technology for data and telecommunication with high transmission capacity.

Broadcast :
To transmit data that is addressed to all members of a local networking group. For example, "browsing" the Network Neighborhood sends broadcast packets to all local devices.

Busy Hour :
An uninterrupted 60-minute period during which the average volume of telecommunications traffic is at its maximum.

Busy Hour Call Attempts (BHCA) :
A measure of dynamic traffic calls that can be attempted in an average busy hour.

Busy Hour Call Completion (BHCC) :
A measure of dynamic traffic calls that can be completed in an average busy hour.

Byte :
A unit of information that is eight bits long. In most computers a character, such as a letter, a number or a typographic symbol is represented by a byte. It can assume a value from 0 (0000 0000) to 255 (1111 1111).