[ovs-dev] Openflow 1.4: Eviction mechanism implementation

Shashwat Srivastava shashwat.srivastava at tcs.com
Fri Aug 8 12:09:26 UTC 2014

Hi All,

I want to incorporate "Eviction mechanism" as per the openflow 
specification 1.4

As per the openflow specification 1.4 (Section, there are three 
eviction flags: importance,lifetime and other. If importance flag is the 
only flag set (lifetime and others not set), eviction is performed 
strictly in order of importance field specified in flow entry, that is 
flow entry with lower importance will be evicted before flow entry with 
higher importance. 

But if all flow entries are of same importance, it has been specified that 
"the eviction mechanism is switch defined ", therefore it is not possible 
to predict in which order flow entries of same importance will get 
At present (without implementation of eviction), when a flow table is 
full, new flow entries are not inserted in the flow table and an error is 
returned to the controller, controller needs time to work on flow table 
and thus may cause a disruption of service. Does this means that, users 
should therefore take care to use importance field wisely to ensure the 
behaviour they expect and avoid disruption of service. It would be great 
help if someone could explain how eviction will be done in this case.

Also kindly suggest action when both the flags for importance and lifetime 
are simultaneously set, as this is missing in the openflow specification 
Thanks in advance for your help and support.

Thanks and Regards,
Shashwat Srivastava
Tata Consultancy Services
Mailto: saloni.jain at tcs.com
Website: http://www.tcs.com
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