Basic Rate Interface (BRI) is a level of data transfer available to users who have an Integrated Services Digital Network (ISDN) connection, and it is mainly used for Internet connectivity. This type of connection is mostly used by home users, small-business owners, and others who need less bandwidth. The Basic Rate Interface is the lower level of service offered, as compared to the Primary Rate Interface (PRI), which has more channels and higher bandwidth. PRI is used primarily by those with larger bandwidth needs, such as a bigger business or a school.
ISDN is a method of communication that uses a digital signal to move data. This can include pure data, video signals, voice signals, and other types of communication. The advantage ISDN has is that it can utilize a standard telephone network system to transmit the different types of traffic at the same time. It uses two types of channels. Bearer channels, known as B-channels, carry the data in various forms, such as voice or video. The Delta channel, referred to as a D-Channel, carries information about the signal itself.
The BRI is considered the entry level with regards to ISDN service. BRI has two B-channels and one D-Channel. The B-Channels can carry 64 Kilobits per second (Kbit/sec), and transmits either data or one digital voice signal. D-Channels can move at a rate of 16 Kbit/sec, and are used to negotiate a call or the signal as well as store information about the signal. The B-channels are often combined to move up to 128 kbit/sec of data at a time. This is also the highest rate of transfer available to Basic Rate Interface users.
The use of ISDN, and subsequently Basic Rate Interface and Primary Rate Interface, varies with regards to frequency of use. BRI is not as popular in the US but enjoys popularity in parts of Europe and Japan, whereas the PRI level of service enjoys a similar rate of use worldwide. In addition, BRI has a different modulation sequence in different parts of the world. In North America, the method is known as 2B1Q and in the rest of the world, the 4B3T standard is used.
Basic Rate Interface can be delivered with physical interfaces. It mostly depends on the specific use of the network as well geographical factors, such as distance, as to which interface will be implemented. The most common format is known as an S/T interface, and it is the easiest to set up and use in home-subscriber networks.