Abstract The apparatus is used for queuing and scheduling ATM cells across an ATM switch. A sustainable cell rate calendar is connected in series with a peak cell rate calendar and cells are scheduled independently in each. The sustainable cell rate calendar guarantees the maximum ATM cell delay is not exceeded. The ATM cells are not placed on the peak cell rate calendar unless the peak cell rate threshold might be exceeded. In this case the cell is scheduled on the peak cell rate calendar and it is this that determines when the cell is sent. In this way, it is possible to guarantee absolute minimum and maximum cell rates of a connection.
Apparatus for queuing and scheduling ATM cells connected to an output side of an ATM switch, comprising first and second calendars connected in series, said first calendar being used to schedule cells for transmission in accordance with a maximum delay value, said second calendar being used to schedule cells for transmission in accordance with a minimum delay value, and comparator means for determining when a cell is to be scheduled on said second calendar.
Claim 2
Dependent Claim
217 words
Apparatus as claimed in Claim 1, wherein said apparatus comprises buffer means connected to an input line upon which ATM cells are received, first control means for receiving for each cell a channel identifier and a path identifier from which a first signal is generated indicative of said maximum delay value, said first calendar in which said cell is scheduled for transmission in accordance with the maximum delay value being used to control a sustainable cell rate, an output line from said first calendar which is connected to an input of said second calendar, second buffer means for receiving ATM cells from said first calendar, and second control means for receiving a channel identifier and a path identifier in respect of the received cell for generating a second signal indicative of said minimum delay value, which is used to schedule the particular cell for transmission on said second calendar for controlling a peak cell rate, wherein, cells are dispatched from said first calendar and are compared by said comparator means against a table of values for a peak cell rate intercell time and a last time the particular cell was transmitted and if said intercell time will be less when said cell is transmitted immediately, said cell is scheduled on said second calendar at said intercell time.
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