Nortel Passport 4400, Using Manual, Page: 122 / 144

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206906-D Rev 00 4.2
AT command set
The de facto standard command language for controlling modems. Developed
by Hayes Microcomputer Products.
Autocall
A configuration option used for switching a voice extension to a single
destination.
B8ZS
Binary 8 Zero Substitution. A T1 zeros code suppression technique, where an
all-zeros byte is replaced with a code of 00011011, and each ones pair is
transmitted with a bipolar violation.
backbone
That part of a network which joins LANs together via bridges and/or routers,
and serves as a communications highway for LAN-to-LAN traffic. The term
may also be applied to that part of a network which carries the heaviest traffic.
BECN
Backwards Explicit Congestion Notification. The BECN bit in the Frame
Relay header of a frame that warns the receiving device that the frames it is
receiving (traveling in the opposite direction) have encountered congestion or
congested resources. Contrast with FECN.
Bit Stuffing
A zeros suppression technique, where bit 7 of every byte is forced to a “1”.
With this method, only 56 kb/s of every 64 kb/s DS0 channel is available for
data. Contrast with B8ZS and HDB3.
BRI
Basic Rate Interface. Refers to the interface between an ISDN subscriber and
the ISDN switch (that is, the local loop). It consists of two 64 Kbit/s
B-channels for user voice/fax or data, and one 16 Kbit/s D-channel for
signaling information.
bridging
Bridging is used to connect LANs at the data link (versus the network)
protocol layer. The Passport 4400 supports transparent bridging, a process of