Connectivity Framework
4 : Connectivity Framework Layer
based filtering in the connectivity infrastructure is required . For example , a sensor may generate data at a rate of 1000Hz rate , but a user display may not require data at a rate faster than the display refresh rate of , say , 30Hz .
A consumer ’ s desired data rate may change over time or for different data items . By knowing the desired data-rate needs across components , connectivity frameworks can optimize the use of system resources for data distribution . This can result in lower overall system resource footprint and lower system cost .
For IIoT systems , the ability to specify a time-based data subset of interest and automatically optimize the data flows is highly desirable .
4.2.3 PERFORMANCE CONSIDERATIONS
4.2.3.1 REAL-TIME
“ Real time ” is more about deterministic response than it is about fast response . Many systems require low average latency , but real-time systems succeed only if they always respond “ on time ”. This is the maximum latency , and can be expressed as the average delay plus the variation or jitter . Even a fast server with low average latency can experience large jitter under load . For real-time operation , the latency needs to be predictable ( i . e . the jitter should be consistently small ).
4.2.3.2 LATENCY AND JITTER VS . THROUGHPUT
Throughput refers to the volume of data distributed per unit time . The throughput demands can vary widely — for example , under load or stress in an emergency situation , there may be a lot more communication compared to normal or steady state operation . Latency and jitter can suffer when throughput demands increase on the connectivity infrastructure without increased capacity . A connectivity framework should be able to meet the latency and jitter requirements for real-time performance as with increasing throughput demand , a core consideration of the quality-of-service function .
For IIoT systems , the latency and jitter vs . throughput tradeoffs should be carefully evaluated , and the limiting factors for throughput and latency should be understood .
4.2.4 SCALABILITY CONSIDERATIONS
4.2.4.1 DATA OBJECTS
When the number of data objects increases , it is no longer practical to send every update to every possible consumer . Connectivity frameworks should support data-object scaling by offering runtime introspection so consumers can choose data objects of interest , and configure producer update distribution to a sparser set currently of interest . A producer can also batch multiple dataobject updates destined for the same consumer to make the data distribution efficient and scalable .
IIC : PUB : G5 : V1.0 : PB : 20170228 - 35 -