Hi, I am doing a basic test of OVS for OVS to NOX connection over SSL.
Setup ======== Machine 1 ( OVS, 10.2.0.111 ) -- connected to NOX over SSL ( NOX installs a flow : forward all packets to CONTROLLER ) NOX : Whenever a packet comes forward it to all connected DPID. Machine 2 ( OVS, 10.2.0.121 ) -- connected to NOX over SSL ( NOX installs a flow : forward all packets to CONTROLLER ) Tests ========== ping 10.2.0.121 9 packets transmitted, 9 received, 0% packet loss, time 8077ms rtt min/avg/max/mdev = 1.897/4.439/22.558/6.409 ms ping -s 1450 10.2.0.121 -c 10 10 packets transmitted, 10 received, 0% packet loss, time 9087ms rtt min/avg/max/mdev = 1.962/2.272/2.668/0.253 ms ping -s 1460 10.2.0.121 -c 10 10 packets transmitted, 8 received, *20% packet loss*, time 9087ms rtt min/avg/max/mdev = 2.128/2.855/5.691/1.104 ms ping -s 1472 10.2.0.121 -c 10 10 packets transmitted, 8 received, 20% packet loss, time 9098ms rtt min/avg/max/mdev = 1.995/2.332/2.684/0.225 ms ping -s *1473* 10.2.0.121 -c 10 --- CROSSED the MTU size ( PMTU discovery results in 1500 ) 10 packets transmitted, 8 received, 20% packet loss, time 9088ms rtt min/avg/max/mdev = *40.655/40.749/40.900/0.258 ms* ========================= I have tried this experiment 50000 times with the same results. After a packet size of ~1450, I can see packet loss and the moment packet size crosses PMTU, the response time jumps 20 times ( from 2 ms to 40 ms ). I tried to simulate same behavior with a simple tcp client/server. Please see the dump of a packet reception and its response from server. The dump was taken at eth0 of tcp server. 10.2.0.201 ( client ) sends a packet of size of 1448 to 10.2.0.121( server ). =========================== 14:10:14.234892 IP 10.2.0.201.5005 > 10.2.0.121.5001: Flags [P.], seq 744272:745720, ack 16449, win 30720, options [nop,nop,TS val 2180291 ecr 2141105], *length 1448* *Immediate ACK from Server Machine* *for 1448 byte packet* -->> 14:10:14.234912 IP 10.2.0.121.5001 > 10.2.0.201.5005: Flags [P.], seq 16449:16481, ack 745720, win 32, options [nop,nop,TS val 2141106 ecr 2180291], length 32 10.2.0.201 ( client ) sends a packet of size of 1548 to 10.2.0.121( server ). =========================== 14:12:20.400152 IP 10.2.0.201.5005 > 10.2.0.121.5001: Flags [.], seq 29513:30961, ack 640, win 30720, options [nop,nop,TS val 2192911 ecr 2153722], *length 1448* * A delayed ACK from Server Machine* *for 1448 byte packet* -->> 14:12:20.439894 IP 10.2.0.121.5001 > 10.2.0.201.5005: Flags [.], ack 30961, win 32, options [nop,nop,TS val 2153730 ecr 2192911], length 0 *Rest of the packet (100 bytes)* 14:12:20.440539 IP 10.2.0.201.5005 > 10.2.0.121.5001: Flags [P.], seq 30961:31061, ack 640, win 30720, options [nop,nop,TS val 2192911 ecr 2153722], length 100 *Immediate ACK from Server Machine* *for 100 byte packet* -->> 14:12:20.440563 IP 10.2.0.121.5001 > 10.2.0.201.5005: Flags [.], ack 31061, win 32, options [nop,nop,TS val 2153730 ecr 2192911], length 0 thanks Vishal
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