[ovs-discuss] How to split in group table with select type

Ben Pfaff blp at ovn.org
Mon Jan 25 16:40:41 UTC 2016


On Mon, Jan 25, 2016 at 10:24:38AM -0500, Jiaqi Zheng wrote:
> My ovs version is 2.3.0.
> 
> I know if the group table is configured with different split weight. The
> flow is splitted through different outport according to configured split
> weight.
> 
> In my experiments, it seems like the split is flow-based, rather than
> packet-based. right ?

Yes.

> Also could I know how to hash during split process ? According destination
> MAC address ? Is there any document to tell that ?

### Q: How does OVS divide flows among buckets in an OpenFlow "select" group?

A: In Open vSwitch 2.3 and earlier, Open vSwitch used the destination
   Ethernet address to choose a bucket in a select group.

   Open vSwitch 2.4 and later by default hashes the source and
   destination Ethernet address, VLAN ID, Ethernet type, IPv4/v6
   source and destination address and protocol, and for TCP and SCTP
   only, the source and destination ports.  The hash is "symmetric",
   meaning that exchanging source and destination addresses does not
   change the bucket selection.

   Select groups in Open vSwitch 2.4 and later can be configured to
   use a different hash function, using a Netronome extension to the
   OpenFlow 1.5+ group_mod message.  For more information, see
   Documentation/group-selection-method-property.txt in the Open
   vSwitch source tree.  (OpenFlow 1.5 support in Open vSwitch is still
   experimental.)



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