[ovs-discuss] UDP datagram size effect at flow table hitting

병욱이 nimdrak at gmail.com
Wed Sep 11 14:04:03 UTC 2019

I did a small experiment with ONOS 3.0.5, OVS 2.0.2(OF 1.0), mininet 2.3.0d5

I found when making flow rule about L4 port, hitting flow table
doesn't work properly.

For example, about UDP flow, ip_src=, ip_dst=, udp_dst=50000

       1)  cookie=0x4c0000ef7faa8a, duration=332.717s, table=0, n_packets=8974,
        n_bytes=557090858, idle_age=153, priority=65050,ip,nw_dst=

        2) cookie=0x4c0000951b3b33, duration=332.636s, table=0, n_packets=10,
        tp_dst=50000 actions=output:3

Although the flow rule 2 have higher priority and more match field,
the flow rule 2 was hit.

When doing trouble shooting, I found the UDP datagram size affect the result.

For 63kBytes datagram, the flow rule 1 is hit.

However for 1500Bytes datagram, the flow rule 2 is hit.

I think the datagram size degrade the match of OVS but I don't know exactly

Could you give me a little hint?

Thanks :)

-Byounguk Lee.

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