Abstract: A method may include receiving a data unit and identifying a state of a memory storing data units. The method may include selecting a threshold value having a first threshold unit or a second threshold unit based on the state of the memory. The method may include comparing the threshold value to a queue state using the first threshold unit if the memory is in a first state. The method may include comparing the threshold value to the queue state using the second threshold unit if the memory is in a second state.

Abstract: A method may include receiving a data unit and identifying a state of a memory storing data units. The method may include selecting a threshold value having a first threshold unit or a second threshold unit based on the state of the memory. The method may include comparing the threshold value to a queue state using the first threshold unit if the memory is in a first state. The method may include comparing the threshold value to the queue state using the second threshold unit if the memory is in a second state.

Abstract: A method may include receiving a data unit and identifying a state of a memory storing data units. The method may include selecting a threshold value having a first threshold unit or a second threshold unit based on the state of the memory. The method may include comparing the threshold value to a queue state using the first threshold unit if the memory is in a first state. The method may include comparing the threshold value to the queue state using the second threshold unit if the memory is in a second state.

Abstract: Quality of Service (“QoS”) variables for predetermined protocol Type data units are stored in a cache memory. For data units that are associated with a flow, thirteen bytes selected out of the Internet Protocol (“IP”) header are employed as at least a portion of a key to perform a cache lookup to obtain at least one Quality of Service variable from the cache. Both routing and QoS information may be stored in the cache for retrieval upon a single lookup operation.

Abstract: A clock crossing FIFO capable of functioning regardless of relative clock frequencies on the write and read sides. Toggle signals are utilized to cross the clock boundaries. The number of write counts which have been accrued but not acknowledged by the read side are tracked, and this number is stored as of the issuance of a write toggle. Upon toggle receipt on the read side, this number is latched as a measure of the number of data units which can be read from the FIFO. At the same time, the toggle is returned to the write side for decrementing the number of write counts outstanding by the number conveyed to the read side. Similar circuitry is employed for conveying to the write side circuitry the number of data units which have been read by the read side circuitry. The presently disclosed FIFO and associated circuitry operates independent of relative clock speeds, and the particular size of the FIFO is scalable.