[ovs-discuss] Way of handling rules at the OVS flow-table is there any time order?

Jordi Baranda jorge.baranda at cttc.es
Thu Nov 19 11:20:01 UTC 2020

Dear OVSers,

I am working in adding some restoration capabilities to my SDN 
controller app. I am in the design phase and I thinking of the 
implications of using break-before-make or make-before-break strategies.

If I use break-before-make, there is no problem because I replace the 
rules and that is. However for the make-before-break approach, I foresee 
that there will be some flow rules with the same match fields but 
different action fields. (e.g, t0: in_port: 3 -> out_port: 2 vs t1: 
in_port: 3 -> out_port:4, where t0 means time0 and t1 means time1 and t1 
 > t0 (older time instant) ).  I know I could handle that with 
priorities but I think this may add further complexity to the SDN 
controller app.

I am wondering if I can skip this treatment at the SDN controller app 
making use of how OVS applies/evaluates rules in the flow table. More 
specifically, rules in the flow table of OVS (for the same priority) are 
evaluated in any time order? That is, OVS is considering "t1 rule" 
(which is more recent than the one of t0) before than "t0 rule"  
(however, t0 rule will be erased afterwards)? Or are the flow-rules in 
the flow table ordered/evaluated "randomly"? Additionally, has this 
changed through the OVS versions?

Thanks in advance for your suggestions,




*Jorge Baranda*
Senior Researcher, MsC
jorge.baranda at cttc.cat <mailto:jorge.baranda at cttc.cat>


Centre Tecnològic de Telecomunicacions de Catalunya (CTTC)
Av. Carl Friedrich Gauss, 7 - Building B4
08860 - Castelldefels
Tel.: +34 93 645 29 00


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