Primary Rate ISDN (PRI)

Primary Rate ISDN consists of twenty-three 64K B channels and 1 64K D channel. The B channels are used to carry voice or data and the D channel is used for protocol negotiation. Using Multilink PPP (MLP) two ISDN devices are able to negotiate Bonding. This allows them to inverse multiplex the B channels to achieve greater than 64K throughput. Primary Rate ISDN is actually delivered over a T1 line.