Abstract: Methods and apparatus are disclosed for using a programmable lookup word generator to produce a lookup word for use by a content-addressable memory. The programmable lookup word generator includes a profile memory which contains instructions on how to build a particular lookup word. The programmable lookup word generator receives a set of information and possibly other operands typically including a profile selection. Based on the profile selection, a set of instructions is retrieved from the profile memory. Control logic uses this set of instructions to build the lookup word by extracting portions of the received information and other operands and ordering these extracted portions possibly with additional information to build the lookup word. The lookup word is then used by a CAM, typically to classify the received set of information and other operands. In one context, the CAM produces a packet classification indication in a communication or computer system.

Abstract: Methods and apparatus are disclosed for implementing and using multiple virtual portions of an associative memory. An associative memory is programmed with multiple sets of entries, each of the multiple sets of entries including a different unique decoder field. A piece of information is received including a data item. A decoder field is identified. The decoder field and the data item are typically included in a lookup word used in a lookup operation in the associated memory, with the decoder field identifying which of the multiple sets of entries to search based on the data item. In one implementation, a nested condition associated with the data item is identified, and in response, multiple lookup words are generated with a predefined set of decoder fields for the data item. Multiple levels of decoder fields may be used to identify multiple subsets of entries within one of the multiple sets of entries.

Abstract: Methods and apparatus are disclosed for matching a string with multiple lookups using a single associative memory, such as, but not limited to binary and ternary content-addressable memories (CAMs). In one implementation, an information string is partitioned into multiple segments. A first lookup operation is performed on the associative memory using the first segment to produce a first associative memory result, which is used as input to a memory lookup operation to produce a first result. The first result can be programmed to have any desired value or length. This first result along with a second segment of the information string is then used as input to the same associative memory to produce a second associative memory result, which is typically used as input to a memory lookup operation to produce a second result. This process can be repeated for an arbitrary or predetermined number of times.

Abstract: Methods and apparatus are disclosed for maintaining netflow statistics using an associative memory to identify and maintain netflows. A lookup operation is performed on a set of associative memory entries to produce an associative memory result directly or after a subsequent memory read operation. In response to the associative memory result corresponding to a not found condition, an entry is added to the set of associative memory entries. Otherwise, a statistics entry in the set of statistics is updated based on the associative memory result. In one implementation, the associative memory is programmed with a set of permanent netflow entries and a set of dynamic or nonpermanent netflow entries, which are maintained in the form of a queue or ring buffer. In one embodiment, when the number of dynamic entries exceeds a threshold value, one or more of the dynamic entries and their corresponding statistics values are flushed.