Hello all,
I test Open vSwitch in the following scheme: I use 2 hosts directly connected to OVS and external OpenFlow Controller. Host1 generates UDP datagrams with sequential ports towards Host2, Host 2 listens for these UDP datagrams. In responce to every UDP datagram OVS generates Packet_In and Controller sends Flow_Mod back with L4 granularity (so for every pair of UDP port numbers it installs separate flow). I send bunch of UDP datagrams from Host1 and calculate how many of them arrived to Host2. I tried both with detached controller and running in the same machine as OVS. I tested it on different machines (in Mininet and with separated real hosts). I use out-of-band option for controller and disable-in-band=true. Starting some number of packets ( around >300) packet drops are observed. For instance, if I generate 500 UDP packets in 120 ms only around 350 of them arrive to Host2 (Subsequent packets of the same flow can arrive to Host2, but first packets of flows always experience drops) ovs-ofctl dump-aggregate show that all the flows are installed but only part of packets are processed through them: NXST_AGGREGATE reply (xid=0x4): packet_count=356 byte_count=42364 flow_count=500 ovs-ofctl dump-ports also shows that 500 packets arrive on ingress interface and only 356 leave egress. ovs-dpctl show –s shows the same – 500 flows installed and 356 packets processed. Also I tried to replace Flow_Mods with Packet_Out messages for every packet, but I experienced the same drops. It seems like OVS starts dropping packets after some threshold (or buffer overload). Is there any possibility to debug these drops and maybe to manipulate ingress buffer sizes (or queue priorities) in order to avoid such drops? -- Best regards, Anton Matsiuk
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