Basic Rate Interface (BRI, 2B+D, 2B1D) or Basic Rate Access is an
Integrated Services Digital Network (ISDN) configuration intended primarily for use in
subscriber lines similar to those that have long been used for
voice-grade telephone service.
As such, an ISDN BRI connection can use the
existing telephone infrastructure at a business.
The BRI configuration provides 2 data (bearer) channels (
B channels) at 64 kbit/s each and 1 control (delta) channel (
D channel) at 16 kbit/s. The B channels are used for
voice
The human voice consists of sound made by a human being using the vocal tract, including talking, singing, laughing, crying, screaming, shouting, humming or yelling. The human voice frequency is specifically a part of human sound producti ...
or user
data
In the pursuit of knowledge, data (; ) is a collection of discrete values that convey information, describing quantity, quality, fact, statistics, other basic units of meaning, or simply sequences of symbols that may be further interpret ...
, and the D channel is used for any combination of data,
control/signaling, and
X.25
X.25 is an ITU-T standard protocol suite for packet-switched data communication in wide area networks (WAN). It was originally defined by the International Telegraph and Telephone Consultative Committee (CCITT, now ITU-T) in a series of drafts a ...
packet networking. The 2
B channels can be aggregated by
channel bonding
In computer networking, link aggregation is the combining ( aggregating) of multiple network connections in parallel by any of several methods, in order to increase throughput beyond what a single connection could sustain, to provide redunda ...
providing a total data rate of 128 kbit/s. The BRI ISDN service is commonly installed for
residential
A residential area is a land used in which housing predominates, as opposed to industrial and commercial areas.
Housing may vary significantly between, and through, residential areas. These include single-family housing, multi-family resi ...
or small business service (ISDN
PABX) in many countries.
In contrast to the BRI, the
Primary Rate Interface (PRI) configuration provides more
B channels and operates at a higher
bit rate
In telecommunications and computing, bit rate (bitrate or as a variable ''R'') is the number of bits that are conveyed or processed per unit of time.
The bit rate is expressed in the unit bit per second (symbol: bit/s), often in conjunction ...
.
Physical interfaces
The BRI is split in two sections:
a) in-house cabling (S/T reference point or S-bus) from the ISDN terminal up to the
network termination 1 (NT1) and
b) transmission from the NT1 to the central office (U reference point).
* The in-house part is defined in
I.430 produced by the
International Telecommunication Union
The International Telecommunication Union is a specialized agency of the United Nations responsible for many matters related to information and communication technologies. It was established on 17 May 1865 as the International Telegraph Unio ...
(ITU). The S/T-interface (
S0) uses four wires; one pair for the
uplink and another pair for the
downlink. It offers a full-duplex mode of operation. The I.430 protocol defines 48-bit
packets comprising 16
bits from the B1 channel, 16 bits from B2 channel, 4 bits from the D channel, and 12 bits used for
synchronization
Synchronization is the coordination of events to operate a system in unison. For example, the conductor of an orchestra keeps the orchestra synchronized or ''in time''. Systems that operate with all parts in synchrony are said to be synchronou ...
purposes. These packets are sent at a rate of , resulting in a gross
bit rate
In telecommunications and computing, bit rate (bitrate or as a variable ''R'') is the number of bits that are conveyed or processed per unit of time.
The bit rate is expressed in the unit bit per second (symbol: bit/s), often in conjunction ...
of 192 kbit/s and - giving the data rates listed above - a maximum possible throughput of . The S
0 offers point-to-point or point-to-multipoint operation; Max length: 900m (point-to-point), 300m (point-to-multipoint).
* The
Up Interface uses two wires. The gross bit rate is 160 kbit/s; 144 kbit/s throughput, 12 kbit/s sync and 4 kbit/s maintenance. The signals on the U reference point are encoded by two modulation techniques: 2B1Q in North America, Italy and Switzerland, and 4B3T elsewhere. Depending on the applicable cable length, two varieties are implemented,
UpN and
Up0. The
Uk0 interface uses one wire pair with
echo cancellation for the long
last mile cable between the
telephone exchange
telephone exchange, telephone switch, or central office is a telecommunications system used in the public switched telephone network (PSTN) or in large enterprises. It interconnects telephone subscriber lines or virtual circuits of digital syste ...
and the
network terminator
In electronics, electrical termination is the practice of ending a transmission line with a device that matches the characteristic impedance of the line. Termination prevents signals from reflecting off the end of the transmission line. Reflect ...
. The maximum length of this BRI section is between 4 and 8 km.
External links
*{{cite web, url=http://www.birds-eye.net/definition/b/bri-basic_rate_interface.shtml , title=BRI defined on birds-eye.net , access-date=2012-08-25 , url-status=dead , archive-url=https://web.archive.org/web/20120825163144/http://www.birds-eye.net/definition/b/bri-basic_rate_interface.shtml , archive-date=2012-08-25
Integrated Services Digital Network