Kabushiki Kaisha Toshiba

Cabletron Systems, Inc.

Kohei Abe

Koichi Tanaka

Robert E Thomas

Peter J Roman

Shinichi Mizuguchi

Tong-Bi Pei

In the tail address in a first queue in a pointer table, the head address in a second queue is stored as pointer information. In the tail address in the second queue, the tail address in the first queue is stored as pointer information. Pointer information about the head address in the first queue is stored in the head address in a storage area. In the tail address, pointer information about the tail address in the second queue is stored.

Queue control device for and queue control method of controlling a plurality of queues

A scheduler in accord with the invention schedules available bit rate (ABR) traffic over an asynchronous transfer mode (ATM) link in such a manner as to provide circuits having the ABR traffic service a minimum cell rate (MCR) that may be greater than zero. The scheduler uses static scheduling information to schedule traffic for high priority services, such as constant bit rate service. The static information also specifies transmit opportunities for an ABR circuit, in a manner analogous to that for CBR traffic. The statically scheduled transmit opportunities provide a negotiated minimum cell rate that is greater than zero, for the ABR circuit. The scheduler maintains dynamic scheduling information, which it uses to schedule traffic in otherwise available transmit times. For example, the scheduler may use the dynamic information to create a work list of virtual circuit connections for ABR service. During any cell transmit time that is not used by a higher priority service (e.g. CBR or MCR), the scheduler goes to the work list to find a circuit with a cell ready for transmission and initiates transmission of the cell for that circuit. The ABR circuit having a non-zero MCR receives service from the statically scheduled opportunities and from the dynamically scheduled opportunities.

Non-zero minimum cell rate for available bit rate ATM service

An apparatus and method for generating a congestion indication bit to be written to the CI field of a backwards RM ATM cell to be transmitted by a network interface utilizes a slot.sub.-- type congestion signal for indicating that the number of slots available for receiving cells is below a threshold limit, and a CI.sub.-- VC signal for indicating that the buffer space consumed by cells received on a particular VC has passed a threshold value. The CI bit in a backward RM cell for the VC when either the slot.sub.-- type congestion signal is set or the CI.sub.-- VC bit is set or the EFCI bit was set in the last data cell received by the network interface or the CI bit was set in the last forward RM cell transmitted by the network interface.

Apparatus and method for setting a congestion indicate bit in an

The communication control apparatus can suppress the maximum cell intervals and further enables the simultaneous transmit decision processing for a plurality of the virtual lines. A communication control apparatus used for asynchronous communication executed by setting a transmit enable time at which data can be transmitted to each of a plurality of virtual lines, and by deciding the virtual lines having transmissible data on the basis of the transmit enable times comprises: a time comparing section (1) for comparing the transmit enable times set to a plurality of the virtual lines having transmissible data, respectively with transmit decision time at the same time, to generate comparison result signals; a flag holding section (3) for holding the comparison result signals generated by the time comparing means for each of a plurality of the virtual lines, and erasing the held comparison result signal of a predetermined virtual line in response to a clear signal; and a priority deciding section (5), when a plurality of data-transmissible comparison result signals are held in the flag holding means at the same transmit decision time, for deciding priority sequence of the virtual lines corresponding to the comparison result signals on the basis of rewritable priority flags decided for each of a plurality of the virtual lines to decide one of the virtual lines to be transmitted, and for outputting a clear signal to the flag holding means to erase the comparison result signal of the decided virtual line.

Communication control apparatus

A communication control system for providing and registering a plurality of virtual circuits and sequentially transferring cells via the virtual circuits in response to request for transferring cells in an synchronous transfer mode is described. The communications control system comprises a device for determining whether or not it is permitted to transfer a cell via each virtual circuit having been registered in order to control the rate of transferring cells via the virtual circuit, and a device for erasing the registration of each virtual circuit if no cell is transferred via the virtual circuit for a predetermined time period after latest transmission on the basis of information for controlling the rate of transferring cells via the virtual circuit. In this configuration, erroneous operation is prevented which originates from overflow occurring in a counter for counting the present time.

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Yokohama, Japan

Kohei Abe