We have been referring the RYU source code to understand the OF Specific 
instructions primarily OFV1.1, OFV1.2, OFV1.3,OFV1.4 and OFV1.5.
Currently while simulating the tests with Instruction OFPIT_STAT_TRIGGER
(Specification EXT-335) we got couple of Open points to understand more on 
the implementation part which needs more clarity to understand. 

As part of the Specification details for the EXT-335 we understand that 
"This Instruction is primarily required to send out Openflow Extensible 
stats (as part of flexible encoding) to Controller based on certain 
thresholds which are user defined". Please correct my understanding for 
the same?

So this is how the Instruction looks  with the bitmap Flags shown below:

enum ofp_stat_trigger_flags {
OFPSTF_PERIODIC = 1 << 0,   /* Trigger for all multiples of thresholds. */
OFPSTF_ONLY_FIRST = 1 << 1, /* Trigger on only first reach threshold. */
/* Instruction structure for OFPIT_STAT_TRIGGER */
struct ofp_instruction_stat_trigger {
uint16_t type; /* OFPIT_STAT_TRIGGER */
uint16_t len; 
uint32_t flags; 
struct ofp_stats thresholds; 
OFP_ASSERT(sizeof(struct ofp_instruction_stat_trigger) == 16);

Based on the above understanding and the current RYU implementation it is 
unclear of how the Flags and thresholds are derived and based on what?
Because if we really see the RYU python scripts for VERSION1.5 we see the 
hardcoded values for duration, idle_time , flow_count, packet_count, and 
byte_count as part of the OXS fields filling.
For our understanding we are not clear on how can we decide on the above 
Fields of when the Instruction trigger needs to set the PERIODIC FLAG or 
ONLY_FIRST flag as part of the FLOW_STATS REPLY To controller.

Much appreciate your response for the same.

Thanks & Regards
Poonam Ghosh
Technical Architect, TCS
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