[ovs-discuss] Concept of facets and subfacets

Ahmed Talha Khan auny87 at gmail.com
Wed Nov 28 05:34:53 UTC 2012


Hey,

While going through the code for OVS data path I could not really
understand the need and functionality of facets and sub-facets. The code
comment on "struct facet" explain it like this.

>From file "ofproto-dpif.c"

"A facet associates a "struct flow", which represents the Open
vSwitch userspace idea of an exact-match flow, with one or more subfacets.
 Each subfacet tracks the datapath's idea of the exact-match flow
equivalent to the facet.  When the kernel module (or other dpif
implementation) and Open vSwitch userspace agree on the definition of a
flow key, there is exactly one subfacet per facet.  If the dpif
implementation supports more-specific flow matching than userspace,
however, a facet can have more than one subfacet, each of which corresponds
to some distinction in flow that userspace simply doesn't understand"

"Each subfacet tracks the datapath's idea of the exact-match flow
equivalent to the facet" ?? What does this means? The comments after this
are obviously based on this line which i dont really understand. Can
anybody explain what Facets are and what they imply ?

-- 
Regards,
-Ahmed Talha Khan
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