This keeps coming up. Signed-off-by: Ben Pfaff <b...@ovn.org> --- Documentation/faq/openflow.rst | 16 ++++++++++++++++ 1 file changed, 16 insertions(+)
diff --git a/Documentation/faq/openflow.rst b/Documentation/faq/openflow.rst index 4a20255daf21..561d793a6692 100644 --- a/Documentation/faq/openflow.rst +++ b/Documentation/faq/openflow.rst @@ -478,6 +478,22 @@ Q: How does OVS divide flows among buckets in an OpenFlow "select" group? Documentation/group-selection-method-property.txt in the Open vSwitch source tree. (OpenFlow 1.5 support in Open vSwitch is still experimental.) +Q: An OpenFlow "select" group isn't dividing packets evenly among the buckets. + + A: When a packet passes through a "select" group, Open vSwitch hashes a + subset of the fields in the packet, then it maps the hash value to a + bucket. This means that packets whose hashed fields are the same will + always go to the same bucket[*]. More specifically, if you test with a + single traffic flow, only one bucket will receive any traffic[**]. + Furthermore, statistics and probability mean that testing with a small + number of flows may still yield an uneven distribution. + + [*] Unless its bucket has a watch port or group whose liveness changes + during the test. + + [**] Unless the hash includes fields that vary within a traffic flow, such + as tcp_flags. + Q: I added a flow to accept packets on VLAN 123 and output them on VLAN 456, like so:: -- 2.20.1 _______________________________________________ dev mailing list d...@openvswitch.org https://mail.openvswitch.org/mailman/listinfo/ovs-dev