Why does the Low Latency 40G Ethernet IP drop non-PTP packets when PTP residence-time update is enabled?

Description

Due to a problem in the Quartus® Standard Edition software version 21.1, you may see the Low Latency 40G Ethernet IP may drop large non-PTP packets when the tx_etstamp_ins_ctrl_residence_time_update (PTP residence-time update) is asserted.

This problem is typically observed with jumbo frames of approximately 3000 bytes or larger. The affected packets may be counted at the RX interface but may not appear at the TX output.

PTP packets themselves may continue to transmit correctly.

This problem is not observed when tx_etstamp_ins_ctrl_residence_time_update (PTP residence-time update) is kept deasserted.

Resolution

A patch (21.1std patch 0.16std) is available to fix this problem for the Quartus Standard Edition Software version 21.1. To request the patch, contact your local Altera support representative.

This problem is resolved in the Quartus Prime Pro Edition Software 26.1. Altera recommends migrating to the latest Quartus Prime Pro Edition Software to address this problem.