Business telecommunications and IT systems

When shown as a suffix, indicates Broadband.

see Bearer.

A BT term.

The address of the premises where, for example, a private circuit or telephone call terminates, but which does not receive the bill.

see A End.

Broadband ISDN as opposed to the narrowband ISDN offered by BRA and PRA.

British Approvals Board of Telecommunications.

The router which directs information from one communication channel to another if the first channel fails.

i) The underlying network structure, usually consisting of a fast protocol such as ATM, which supports another protocol such as Ethernet.

ii) The main part of a network's topology.

Typically, a fibre optic cable (backbone) from which the rest of the system is cabled and connected. Connection to / from the backbone is via bridges and / or routers, and the backbone acts as a communications trunk.

A term used in a general way to mean the transmission medium or channel that links lower speed distribution networks, clusters and systems together.

i) A term for a motherboard. Usually associated with the CPU of a telephone system.

ii) In specific IT terms, the bus that traditionally resides at the back of a network hub chassis.

A transformer for leveling out impedance differences so that a signal generated onto a coaxial cable can transfer onto a twisted pair if necessary.

However, the use of a Balun often results in some level of degradation.

The range of frequencies available for signalling in a communications channel or link.

The capacity is measured in Hertz and expressed as the difference between the highest and lowest limits of the usable frequency range. Often specified as bits per second. The greater the frequency, the greater the speed.

A transmission technique whereby the digital input is applied directly to the transmission media, without the intervention of a modulating device.

Works well where there is a wide bandwidth and the information only needs to travel a short distance, no further than a few hundred cable metres.

Commonly used by LANs and by limited distance modems. Baseband is a more cost-effective solution than Broadband.

The signalling process used to establishe a telephone call.

see Q.931.

One of the two types of ISDN, offering the user 2 x 64k channels.

The other type is Primary Rate Access.

Abbreviated to BRA.

A specific host that is used to intercept packets entering or leaving a network, and the system that any outsider must ordinarily connect with to access a system or service that is inside the network's firewall.

Typically the bastion host must be highly secured because it is vulnerable to attack due to its placement. See Dual Homed Gateway.

see Autonomy.

One signalling element per second.

A Frame Relay term. Committed Burst Size (bits).

The maximum amount of data the network agrees to transfer, under normal conditions, given the time interval (Tc).

A Frame Relay term. Excess Burst Size (bits).

The maximum amount of uncommitted data in excess of Bc that a frame relay network can attempt to deliver during the time interval Tc. The probability of Be data arriving is lower than the probability of Bc data arriving. The network treats Be data as discard eligible.

An error condition on Token Ring networks that can result in the loss of a ring.

Beaconing occurs when there has been an interface failure or a break in the network cabling. Just before the network fails, the malfunctioning station sends out an alarm signal called a 'beacon'.