I have 2 Dell PowerEdge-R620 servers with following configuration Processor: 2 X Intel(R) Xeon(R) CPU E5-2637 v2 @ 3.50GHz RAM: 64GB Storage: 10 SAS drives (10K RPM) with RAID 10. NIC: QUAD Ports 2 X 10GB (INTEL X540-AT2)and 2 X 1GB (INTEL I-350) OS: RHEL 8.3

Both servers are directly connected to each other using cat7 cable via 10G interface. We want to test the network performance for UDP packets matching the size of a VOIP/RTP packet.

server2 is running as iperf3 server server2# iperf3 -s

I get 20%-25% packet loss on receiving side when I run the following on server1 command server1# iperf3 -u --length 238 -t 30 -c server1 -b 0

I don't get any packet loss if I limit bitrate to 200Mbps (b 200M). I start to see the packet loss as soon as bitrate goes beyond 200Mbps.

NIC driver and firmware are latest. Cable has tested good. #tuned-adm list shows that the current active profile: throughput-performance.

ethtool -g eno1 shows that ring RX/TX set to 512. Changing RX/TX to 1024 or 2048 did not make any difference.

iperf3 being a single thread application, I though may be cpu core is getting chocked up and dropping packets. But I see packet loss happening if I run 2 parallel tests with bitrate 200Mbps each.

I see "packet receive errors" and "receive buffer errors" increasing while I run the test.

# netstat -su
IcmpMsg:
    InType0: 5962
    InType3: 2188543
    InType5: 25970
    InType8: 169
    OutType0: 169
    OutType3: 2201341
    OutType8: 6451
Udp:
    798970636 packets received
    488445853 packets to unknown port received
    **50427006 packet receive errors**
    2017757523 packets sent
    **50427006 receive buffer errors**
    0 send buffer errors
    IgnoredMulti: 20927
UdpLite:
IpExt:
    InMcastPkts: 68164
    OutMcastPkts: 621
    InBcastPkts: 20927
    InOctets: 338232375898
    OutOctets: 418403184273
    InMcastOctets: 2628618
    OutMcastOctets: 29705
    InBcastOctets: 3387318
    InNoECTPkts: 1350444521
    InECT0Pkts: 9
MPTcpExt:

Any thoughts?