Cell compliance decision method and apparatus

An apparatus for deciding on the compliance of cells at an input of a switch comprising time-counting means (2) with a predetermined maximum counting range, whose reading determines for an arriving first cell (15) a first arrival time (ta1) and for an arriving second cell (12) a second arrival time (ta2) which is compared by first comparison means (4) with a theoretical arrival time (TAT2) for said second cell (12), said theoretical arrival time (TAT2) being calculated in time-calculating means (6) using said first arrival time (ta1) and a predetermined value of an interarrival period (T), whereby in said first comparison means (4), depending on the result of said therein performed comparison, it is decided whether said second arriving cell (12) is considered compliant (cc) or non-compliant, wherein said apparatus further comprises wrap-counting means (3) for counting the number of wraps of said time-counting means (2) whose readings at said second arrival time (ta2) and at said theoretical arrival time (TAT2) being usable for a determination whether a wrap occurred between said theoretical arrival time (TAT2) and said second arrival time (ta2), the result of that determination being usable for the decision whether to use said comparison in said first comparison means (4) for deciding whether said second arriving cell (12) is considered compliant (cc) or non-compliant, or whether to consider said second arriving cell (12) compliant (cc) or non-compliant without performing said comparison;

• further comprising state-determination means (14) which on a timely regular basis with a predetermined repetition period (TR) initiates a process (bp) which effects an artificial second arrival time (ta2) for which the reading of the wrap-counting means (3) is determined, which together with the reading of said wrap-counting means (3) at the theoretical as arrival time (TAT2) is usable for the determination whether a wrap occurred between said theoretical arrival time (TAT2) and said artificial second arrival time (ta2), the result of that determination being usable for the decision whether to use said comparison in said first comparison means (4) for deciding whether said second arriving cell (12) is considered compliant (cc) or non-compliant, or whether to consider said second arriving cell (12) compliant (cc) or non-compliant without performing said comparison, and wherein the repetition period (TR) is at maximum the time between two wraps of the time-counting means (2) multiplied with the maximum reading of the wrap-counting means (3) minus 2.