Cabletron Systems, Inc.

Digital Equipment Corporation

Enterasys Networks, Inc.

Shinichi Mizuguchi

Koichi Tanaka

Peter J Roman

Wing Cheung

Robert E Thomas

Douglas M Washabaugh

Theodore L Ross

Kohei Abe

A method and system for requesting an interrupt from a host system to service an adapter connected to the host system and a data interface. Data packets, including one or more data cells, are transferred between the data interface and the host system. The host system includes a host memory that includes a plurality of memory slots to store data packets transferred between the data interface and the host system. It is determined when a transfer of data has resulted in an occurrence of an interrupt event. An interrupt event occurs when the transfer of data includes a transfer of a data cell between the data interface and the host system and the data cell is defined to be an end of a data packet. In response to the occurrence of an interrupt event, it is determined whether to generate an interrupt request to the host system. This step of determining includes determining whether a predetermined interval of time has elapsed since the host system last processed an interrupt request or determining whether a predetermined number of interrupt events have occurred since the host system last processed an interrupt request. If the predetermined interval of time has elapsed or the predetermined number of events has occurred, respectively, the interrupt request from the adapter to the host system is generated.

Method and apparatus for performing TX raw cell status report frequency and interrupt frequency mitigation in a network node

A time-based and event-based interrupt frequency mitigation scheme is provided. A holdoff event counter is programmed to count a holdoff event count corresponding to a number of interrupts. A holdoff timer is programmed to time a holdoff interval representing the time period to elapse before the generation of an interrupt request to the host system can occur. When a data transfer request associated with the transfer of data from or to the host system is serviced and results in the occurrence of an interrupt event, the holdoff event counter is modified by one. If either the holdoff event counter or the holdoff timer has expired and the interrupt is enabled, an interrupt request to the host system is generated. In response to such interrupt request generation, the interrupt is processed and both the holdoff event counter and the holdoff timer retriggered.

Method and apparatus for performing interrupt frequency mitigation in a

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

A mechanism by which interrupt frequency mitigation is combined with transmit raw cell status report frequency mitigation is presented. A tx raw cell status report is allowed to occur for only every N raw cell tx slots consumed. When the rate of interrupt requests is mitigated in accordance with holdoff parameters including a holdoff event count corresponding to X interrupt events and a holdoff time interval, and the raw cell status report counts as an interrupt event, an interrupt request is generated for an enabled interrupt if N*X events has occurred or the holdoff time interval has elapsed.

Method and apparatus for performing TX raw cell status report frequency

In a network node having a host system coupled to a network by an adapter, VC-specific congestion is detected and reported to the host system. The host memory includes rx slots or buffers, each corresponding to one of one or more supported slot types. Per-VC slots consumed counters are maintained to count slot consumption for each active VC. Free buffer FIFOs are maintained for each of the one or more slot types, which have a predetermined congestion threshold associated therewith. Entries in each free buffer FIFO correspond to an rx slot posted by the host system. When a new rx slot or buffer in host memory is to be allocated to an incoming cell received on a given VC, the slots consumed counter is compared to the predetermined congestion threshold. If they are equal, the VC is at threshold level and the incoming cell is discarded and a report is sent to the host system. If the slots consumed counter is below threshold, a new rx slot is allocated for the reception of the data and the slots consumed counter is incremented. If the VC is credit-based flow control enabled and the slots consumed counter is below threshold, a credit is returned. If the VC is credit-based flow control enabled and the slots consumed counter is greater than or equal to the threshold, the credit return is deferred until the counter falls below threshold.

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Kawasaki, Japan

Shinichi Mizuguchi