Description: This attribute specifies the high priority Early Packet Discard (EPD) offset for connection queues. On ATM IP FPs a given connection queue is associated with one of eight emission priorities (EP). These include six unshaped EPs, one exclusive VBR shaper EP and one ABR/VBR shaper EP. This attribute specifies the EPD offset for the exclusive VBR shaper EP and the first four (higher priority) unshaped EPs.

This offset is used to derive a connection EPD threshold for a given Congestion Control (CC) level by subtracting the offset from the All Packet Discard (APD) threshold at the same CC level. The APD thresholds are themselves derived from the transmit queue limit.

The EPD threshold only applies to a connection if the txPacketWiseDiscard feature is requested. The txPacketWiseDiscard feature can be enabled only if the transmit queue limit is at least 5.71 times the EPD offset. This ensures that the derived EPD threshold will never be less than 17.5 % of the transmit queue limit. If this condition is not satisfied, txPacketWiseDiscard for the connection will be automatically disabled.

Due to the above constraint, if the operator wishes to decrease the transmit queue limit and still have txPacketWiseDiscard enabled on the connection then this offset must be set to a lower value that meets the above requirement.

Due to hardware granularity the actual value of the EPD offset may not match exactly the value provisioned. The actual value is displayed under the ATM Connection Administrator service category subcomponents on ATM IP FPs.

This attribute does not apply to CQC FPs.