BRI ISDN Uses

The most common uses for BRI ISDN (Basic Rate Interface Integrated Services Digial Network) in the US are for dial backup for FR (Flat Rate Service) and for videoconferencing. BRI consists of two bearer channels for customer voice or data at 64 kbps. In addition, it has one 16 kbps signaling channel. It runs over a single pair or twisted wires between the customer and the telephone company.

Deployment of BRI ISDN is higher in Europe and Japan than in the US, where it never reached more than 1% penetration. It was complex to install, telephone companies charged usage fees for ISDN data calls, and the initial lack of widespread availability greatly hindered acceptance of ISDN, particularly among consumers.

France, Germany, Japan, and Switzerland are widely acknowledged to have a large base of BRI ISDN customers. In Europe, BRI ISDN is sometimes referred to as ISDN 2 because it has two bearer channels. Consumers in these countries use it for voice calls and Internet access. The absence of flat-rate pricing on switched services made per-unit charges for dial-up Internet access more acceptable.

Because prices of BRI lines are low compared to PRI (Primary Rate Interface with 24-channel) service, many enterprises use BRI for videoconferencing. To achieve adequate speed for acceptable quality, they bond 3 or 4 BRI circuits together. Bonding is the combination of multiple lines to increase bandwidth. For example, bonding the two bearer channels provides 128 kb of speed (2 x 64). Most organizations bond 3 or 4 circuits together for acceptable video quality at 384 kbps (3 x 128) or 512 kbps (4 x 128).

In bonded circuits, the signaling channel sends bits from each bearer channel sequentially on the ISDN circuits. People viewing the video see a continuous stream of images. To initiate the calls, the video equipment dials the telephone numbers at the remote BRI-equipped video system. Telephone companies charge per-minute fees for these video calls. The conference is ended when one party hangs up. Because it is a switched service, organization are not limited to having video calls to sites on their private networks.

Another application for BRI ISDN is backup access to FR networks in case the dedicated access line for the FR network fails. In these applications, the router usually automatically dials into the FR network when it senses that the dedicated access line is down. On data services, BRI equipment is required at both ends of the call. However, BRI-equipped voice services can call anyone on the PSTN. ISDN is not required at each end of voice calls.