Hello, I would like to verify the RoCEv2 Congestion Management on my system following the HowTo Configure Resilient RoCE End-to-End Using ConnectX-4 and Spectrum (No QoS) article. However, I cannot find any packets with ECN bit == 11b on my Wireshark.

My setup consists of one host with 100Gb Mellanox CX-5 NIC send traffic to a target with 25Gb Mellanox CX-4 NIC thought my network switch.

All of the elements in my systems have the ECN feature enabled.

I also have another server, with one 25Gb Mellanox CX4 NIC, set to monitoring the target switch port. On this server, I run Wireshark capture. Once the data transfer finishes, I cannot see any packet with ECN bit set to 11 even thought I can find the RoCEv2 CNP packets.

Checking the np_ecn_marked_roce_packets on the target side, I see that the counter is around 40000 packets. So I don’t understand why I cannot find the packet with ECN bit set to 11. On your article, I see that you can capture the packet with ECN = 11b.

I wonder if I need to configure the Mellanox NIC anyway to capture

the packets with ECN = 11b.

Thanks and best regards,

Bao Truong

Hello Bao,

Many thanks for posting your question on the Mellanox Community.

In the post, the monitoring node is using a Mellanox ConnectX-3 Pro, the post was not tested when using a ConnectX-4 adapter.

If possible, please use the same setup as mentioned in the post.

Thank you,

~Mellanox Technical Support