5 Replies Latest reply on Sep 28, 2018 7:14 PM by thull

    When will an ACK generated in RDMA write?



      Recently, I am doing some RDMA write latency test with ConnectX-4 Lx 25G NIC.

      And I have two questions about the testing:

      1. What is the version of RDMA? Is the default RoCEv2?
      2. By default, the RC(reliable) mode is chosen. As required, an ACK is needed from the remote to local, then the local will add an entry to the CQ and the software then know the data has arrived at the remote. I searched with google but didn't find when a MLNX NIC will generate the ACK. I mean, is it generated when the data received by the HCA or after DMA to the host memory? And I assume the ACK is automatically generated by the NIC adapter without any SW  involvement. Is my understanding right?


      Many thanks