Description: This attribute specifies the ATM service category for both directions of the connection.

The constantBitRate service category is intended for real time applications, that is those requiring tightly constrained delay and delay variation, as would be appropriate for voice and video applications. The consistent availability of a fixed quantity of bandwidth is considered appropriate for CBR service. Cells which are delayed beyond the value specified by CellTransfer Delay are assumed to be of significantly reduce value to the application.

The rtVariableBitRate service category is intended for real time applications, that is those requiring tightly constrained delay and delay variation, as would be appropriate for voice and video applications. Sources are expected to transmit at a rate which varies with time. Equivalently, the source can be described as 'bursty'. Cells which are delayed beyond the value specified by CTD are assumed to be of significantly reduced value to the application. Real time VBR service may support statistical multiplexing of real time sources.

The nrtVariableBitRate service category is intended for non-real time applications which have bursty traffic characteristics and which can be characterized in terms of a PCR, SCR, and MBS. For those cells which are transferred within the traffic contract, the application expects a low cell loss ratio. For all connections, it expects a bound on the mean cell transfer delay. Non-real time VBR service may support statistical multiplexing of connections.

The unspecifiedBitRate service is intended for non-real time applications; that is, those not requiring tightly constrained delay and delay variation. UBR sources are expected to be bursty. UBR service supports a high degree of statistical multiplexing among sources. UBR service does not specify traffic related service guarantees. No numerical commitments are made with respect to the cell loss ratio experienced by a UBR connection, or as to the cell transfer delay experienced by cells on the connection.