REAL-TIME SYSTEMS II Real-Time Networking WorldFIP ... - EPFL

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List concept Temporal consistency • ordered collection of consumed variables • lists should not intersect in the system • variables may be periodic or not • periods may be different • temporal consistency may be defined on a list • asynchronous status • Ttx + Tcons ≤ Tvalidity ≤ Ttx + Tprod + Tcons • temporal consistency • = logical AND of all refreshment and promptness statuses ⇒ problems timer Tprod refreshment status variable production variable transmission Ttx variable production time Real-Time Networks – WorldFIP 37 ©2010, J.-D. Decotignie var 1 Tprod1 Ttx1 Tcons1 var 2 Ttx2 Tcons2 t1 Real-Time Networks – WorldFIP 38 time timer Tcons promptness status var 1 var 2 Tprod1 Ttx1 Tcons1 Ttx2 t1 t2 t3 t4 Tcons2 time ©2010, J.-D. Decotignie Temporal consistency (2) Temporal consistency (3) Real-Time Networks – WorldFIP 39 • synchronous statuses • Tvalidity = Tcons • temporal consistency • = logical AND of all refreshment and promptness statuses timer Tprod refreshment status timer Tcons promptness status sync. variable variable prod. variable transm. ⇒ OK as long as the same sync. variable is used for all Ttx sync. variable time ©2010, J.-D. Decotignie variable de synchro Real-Time Networks – WorldFIP 40 V1 V2 V3 V4 variable de synchro promptitude V1 promptitude V2 promptitude V3 promptitude V4 cohérence de consommation ©2010, J.-D. Decotignie
Spatial consistency Temporal behaviour Real-Time Networks – WorldFIP 41 • may only be elaborated on lists • based upon two types of variables • a synchronization variable • its value corresponds to the exchange Nb • a consistency variable for each consumer • bears the exchange Number / indicates for each variable in the list • either the exchange number of the available variable value (maintained detection) or the indication of reception in the current exchange cycle (instantaneous detection) • at the end of variable transfers, the consistency variables are transferred S_list (Exchange Nb=23) variable exchange consistency var.exch. t1 t2 t3 V1 V2 V3 V4 CVi CVz S_list (Exchange Nb=24) ©2010, J.-D. Decotignie Real-Time Networks – WorldFIP 42 • Central polling • Guaranteed transaction time (ID_xxx + RP_yyy) provided each transactions is bounded • Timer T0 • Scheduling algorithm is not specified • Periodic operations possible • Also with multiple periods • No retransmission in case of errors • Except for messages with ack • Oversampling may be necessary to tolerate absence of a value in case of error (vacant sampling) ©2010, J.-D. Decotignie Temporal behaviour (2) Schedulability analysis • Sporadic traffic • Best effort (except for specified explicit requests handled in periodic window) • Handling order not specified (may be FIFO) • 2 priorities • No admission control • Periodic traffic • Assumed to be guaranteed so worst case is to be considered • Variable transfers + non acknowledged messages • Acknowledged messages • Aperiodic (sporadic) traffic • May be analysed in worst case or statistically • Statistics are interesting to take errors (retries) into account Real-Time Networks – WorldFIP 43 ©2010, J.-D. Decotignie Real-Time Networks – WorldFIP 44 ©2010, J.-D. Decotignie
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Page 7 and 8: Specified explicit request (RQ_Inhi
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REAL-TIME SYSTEMS II Real-Time Networking WorldFIP ... - EPFL

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