Method and arrangement for checking the observance of prescribed transmission bit rates in an ATM switching equipment

A circuit arrangement for checking the observance of the transmission bit rates of individual virtual connections for asynchronous transmission of message cells of a fixed length during the course of virtual connections in a switching equipment, the switching equipment accepting the message cells via offering media by means of counter devices individually allocated to the virtual connections, comprising:

• a plurality of counter devices, that respectively correspond to a maximum plurality of virtual connections established via the offering media, respectively allocated to the offering media;
• a read-write memory having a plurality of individual memory areas;
• a calculating means connected to the read-write memory;
• the counter devices being respectively formed of an individual memory area of the plurality of individual memory areas of the read-write memory and of the calculating means that is connected to the read-write memory and that is shared in common by all counter devices;
• a momentary counter reading of a respective counter device, a maximum allowable counter reading, a time particular marking a time of arrival of a most recent message cell of a respective virtual connection and a normed count value under consideration for a respective bit rate class or a call-associated proportionality factor being stored as memory contents in the individual memory areas of the read-write memory;
• upon appearance of message cells, the individual memory areas being individually involved in a control cycle based on a measure of a cell header contained in these message cells and indicating the respective virtual connection;
• means for supplying the memory content of a respective memory area and a current time particular for said updating of the momentary counter reading of the respective counter means to the calculating means during the course of said control cycle;
• upon transgression of the maximum allowable counter reading contained in the memory content just supplied by the just updated counter reading, the calculating means having means for supplying an alarm signal indicating an upward transgression of the transmission bit rate recited for the respective virtual connection and for decrementing the updated counter reading by the constant count value;
• and
• means for transmitting at least the momentary counter reading just updated by the calculating means and potentially decremented by the constant count value and the current time particular into the respective memory area while overriding the previously stored, momentary counter reading or the previously stored time particular.

A method for checking an observance of transmission bit rates of individual virtual connections for asynchronous transmission of message cells of fixed length during the course of virtual connections in a switching equipment, the switching equipment accepting the message cells via offering media by means of counter devices individually allocated to the virtual connections, a respective, momentary counter reading of said counter devices being both incremented by a constant count value as well as being decremented by a variable count value for an updating upon arrival of a message cell belonging to an allocated, virtual connection, said variable count value being proportional to a time difference between a time of arrival of a respective message cell and a time of arrival of a most recently received message cell of a same virtual connection serving as a reference time and being retained for the respective counter means, whereby an upward transgression of a maximum allowable counter reading by an updated, momentary counter reading of a respective counter means is respectively individually monitored for the individual counter means as a criterion for an upward transgression of the transmission bit rate of the respective virtual connection, comprising the steps of:

• providing a plurality of bit rate classes and defining a separate bit rate class for a defined, minimum transmission bit rate and for whole multiples thereof;
• allocating a normed numerical value of one to the bit rate class corresponding to the minimum transmission bit rate, and
• allocating, a normed numerical value corresponding to the whole multiple of the minimum transmission bit rate respectively under consideration to the remaining bit rate classes;
• assigning each of the virtual connections to one of the bit rate classes based on the measure of the transmission bit rate respectively recited therefor;
• utilizing a call-associated proportionality factor for a duration of an existence of a respective virtual connection for calculation of said variable count value, said proportionality factor corresponding to a ratio of a normed count value allocated to the bit rate class under consideration to a normed count value allocated to a highest of the bit rate classes;
• the time difference to be evaluated with the call-associated proportionality factor being calculated from momentary values of a time variable existing at the said times, the momentary value thereof changing within a periodically, repeatedly sequencing counting cycle by one counting step after a respectively defined time interval;
• a transmission duration of a message cell being maximally selected at time intervals;
• and
• in addition to the updating of the counter readings of the counter devices under consideration within a counting cycle undertaken in response to arrival of message cells, the momentary counter readings of the individual counter devices being respectively decremented at least twice by the variable count value under consideration during a course of separate correction cycles and a momentary value of the count variables current being retained for the respective counter device as a new reference time.