Different c5.18xlarge instances with netperf TCP_RR, no significant tuning:

  [ec2-user@ip-10-0-2-191 ~]$ netperf -v 2 -H 10.0.2.52 -t TCP_RR -l 30
  MIGRATED TCP REQUEST/RESPONSE TEST from 0.0.0.0 (0.0.0.0) port 0 AF_INET to 10.0.2.52 () port 0 AF_INET : first burst 0
  Local /Remote
  Socket Size   Request  Resp.   Elapsed  Trans.
  Send   Recv   Size     Size    Time     Rate         
  bytes  Bytes  bytes    bytes   secs.    per sec   

  20480  87380  1        1       30.00    21178.69   
  20480  87380 
  Alignment      Offset         RoundTrip  Trans    Throughput
  Local  Remote  Local  Remote  Latency    Rate     10^6bits/s
  Send   Recv    Send   Recv    usec/Tran  per sec  Outbound   Inbound
      8      0       0      0   47.217   21178.689 0.169     0.169