[ovs-discuss] I want to know how group table select works

Ben Pfaff blp at ovn.org
Tue Aug 2 05:11:16 UTC 2016


Probably your new flows have different source or destination TCP ports.

On Tue, Aug 02, 2016 at 01:57:08PM +0900, 허지민 wrote:
> I'am using 2.5.0
> 
> 2016-08-02 13:08 GMT+09:00 Ben Pfaff <blp at ovn.org>:
> 
> > What version of Open vSwitch are you using?
> >
> > On Tue, Aug 02, 2016 at 11:29:22AM +0900, 허지민 wrote:
> > > Thank you for answering.
> > >
> > > I'm not sure if I understood right.
> > >
> > > The answer is saying that, if I don't change source or destination,
> > bucket
> > > selection won't be redone?
> > >
> > > Well, I am using group table for my project, and each bucket in the group
> > > has
> > > different weight. When I tested group table, I found out that after long
> > > term without networking, the selection has changed and send packets to
> > > different bucket.
> > >
> > > How does weight of the bucket influence the selection???
> > >
> > > 2016-08-02 2:10 GMT+09:00 Ben Pfaff <blp at ovn.org>:
> > >
> > > > On Mon, Aug 01, 2016 at 05:39:10PM +0900, 허지민 wrote:
> > > > > I am working on a project using group table select.
> > > > >
> > > > > I am figuring out how group table select one of the buckets that is
> > added
> > > > > in the group.
> > > >
> > > > This is in the FAQ.
> > > >
> > > > ### 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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