Hi all,
we've been experiencing with OVS and its patch ports, and we set up a
the following case:
One OVS bridge instance (created via add-br) is connected to two
physical interfaces (our two-port Intel X710 NIC), and with an arbitrary
number of patch ports (we used 12,24,36,48, etc.) this OVS bridge
instance is connected to another bridge instance (created via add-br as
well).
For a simple setup, we installed the following rules into the flow tables:
The first OVS (having the physical ports) is receiving traffic from one
of the NIC ports (0), and forwards them to one of the patch ports
(differentiated via VLAN tags). The second OVS bridge instance
immediately loops the packets back on the same patch port where it
received them. Finally, the first OVS bridge instance put these
loop-backed traffic to the other NIC port (1) (see below - hopefully,
ASCII art did not fall into pieces).
+----------+ +---------+
0 | OVS 1 |<---->|0 OVS 2 |
--->| |<---->|1 |
1 | | .... | |
<---| |<---->|12 |
+----------+ +---------+
In this case, where the patch ports are basically "full-duplex" ones,
i.e., OVS 1 sends traffic on each of them, while OVS 2 also passes back
the packets on each of them, we deterministically experienced approx.
10% packet drop (number of patch ports has no impact on this).
However, if we doubled the number of patch ports, and set up OVS 2 to
loop-back the packets on the next patch ports instead, i.e., patch ports
were considered as "simplex" (see below), then the packet loss was not
observed.
+----------+ +---------+
0 | OVS 1 |----->|0 OVS 2 |
--->| |<-----|1 |
1 | | .... | |
<---| |----->|23 |
| |<-----|24 |
+----------+ +---------+
We used the openvswitch kernel module, and DPDK, and the observation
applies to both cases, while we also 'played' with the sending rate as
well to avoid 'overloading'.
Could someone help us to understand this phenomenon?
Best Regards,
Levente
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