478 results about "Ternary content addressable memory" patented technology

The present invention provides for a reconfigurable packet classifier using CAM. The invention is directed to packet classification for switching / routing systems where the router's system resources are limited and the customer requirements from the router are variable. The invention addresses the CAM constraint (e.g. search key width) problems of CAM-based classification systems, by allowing a reconfigurable selection of packet fields and / or payload bits to be used in the definition of the search key. For any given incoming packet, a subset of that incoming packet may be statically chosen to fit that particular CAM architecture and to create a particular CAM search key. This provides router deployment flexibility within networks and, thus, cuts costs.

A system and method is provided for automatically identifying and removing malicious data packets, such as denial-of-service (DoS) packets, in an intermediate network node before the packets can be forwarded to a central processing unit (CPU) in the node. The CPU's processing bandwidth is therefore not consumed identifying and removing the malicious packets from the system memory. As such, processing of the malicious packets is essentially “off-loaded” from the CPU, thereby enabling the CPU to process non-malicious packets in a more efficient manner. Unlike prior implementations, the invention identifies malicious packets having complex encapsulations that can not be identified using traditional techniques, such as ternary content addressable memories (TCAM) or lookup tables.

Disclosed is a method and system for multi-character multi-pattern pattern matching. In the multi-character multi-pattern pattern matching method, patterns in an input stream are detected by transitioning between states of a “compressed deterministic finite state automaton (DFA)”, with each transition based on multiple characters of the input stream. The compressed DFA is created by compressing an original DFA, such as an Aho-Corasick DFA, such that each state of the compressed DFA represents multiple consecutive states of the original DFA and each transition between the states of the compressed DFA is a combination of all of the transitions between the multiple consecutive states of the original DFA. This method can be implemented using a Ternary Content-Addressable Memory (TCAM) to store the transitions of the compressed DFA and compares the transitions with multiple characters of an input stream at a time to detect patterns in the input stream.

Disclosed is an apparatus and method for distributing traffic to one or more selected cache systems or servers. In general terms, a content addressable memory (e.g., a TCAM) is utilized to distribute traffic among a plurality of cache systems or servers. The content addressable memory is populated with a plurality of entries. Each entry within the content addressable memory generally indicates an action to be performed on a packet, such as to redirect the packet or to forward the packet to its original destination. When the action indicated by the content addressable memory is to redirect the packet, the content addressable memory also indicates where (e.g., to which cache system) to redirect the packet.

Methods and apparatus are provided for classifying data packets in data processing systems. A first packet classification method determines which of a plurality of predefined processing rules applies to a data packet, where each rule is associated with a range of possible data values in each of a plurality of dimensions (X,Y) corresponding to respective data items in the packet format. For each dimension (X,Y), it is determined which of a set of predefined basic ranges contains the corresponding data value (I1, I2) from the packet, where the basic ranges correspond to respective non-overlapping value ranges between successive rule range boundaries in the dimension. For the basic range so determined for each dimension, a corresponding basic range identifier is selected from a set of predefined basic range identifiers corresponding to respective basic ranges in that dimension. For each of at least two dimensions (X,Y), the basic range identifiers comprise respective pD-bit strings generated independently for that dimension by a process of deriving a primitive range hierarchy based on the rule ranges in that dimension. The resulting basic range identifiers, one for each dimension, are then combined to produce a search key which is supplied to a ternary content-addressable memory (5). In the memory (5), the search key is compared with a set of ternary rule vectors, each associated with a particular rule and derived for that rule from the aforementioned hierarchies, to identify at least one rule which applies to the data packet. A second method classifies data packets according to the values in respective data packets of a single, predetermined data item (DA) in the data packet format, where a plurality of classification results are predefined for respective ranges of values of the data item (DA). Here the data item (DA) in the packet is first segmented. The resulting segments are then equated to different dimensions (X,Y) of a multidimensional packet classification problem and are processed in a similar manner to identify a classification result for the packet.

The invention provides a multilevel flow table-based Openflow message forwarding method and a multilevel flow table-based Openflow message forwarding system. The method comprises the following steps of: at least constructing a primary flow table, a secondary flow table and a tertiary flow table sequentially in series, wherein the primary and secondary flow tables are constructed in a ternary content addressable memory (TCAM) form, the tertiary flow table is constructed in a Hash table form, and the primary, secondary and tertiary flow tables can be used independently or in a combined way; searching for forwarding operation over a message on the basis of the primary, secondary and tertiary flow tables; and forwarding the message according to the forwarding operation. Particle sizes of the primary, secondary and tertiary flow tables are decreased, and the tertiary flow table is constructed in the Hash table form, so that the tertiary flow table can acquire more flow items, and the system cost is controlled.

The number of content addressable memory (CAM) lookups is reduced from two to one. Each side (left and right sides) of a CAM is programmed with network addresses, such as IP addresses, based on certain bits of the network addresses. These bits of the network addresses (which represent packet routes) are examined and used to determine whether the particular network address is to be placed on the left or right sides of the CAM. The grouping of certain network addresses either on the left or right sides of the CAM can be performed by examining an individual bit of each network address, by performing an exclusive OR (XOR) operation on a plurality of bits of each network address, and / or by searching for bit patterns of the network address in a decision table. Network addresses that cannot be readily assigned to a particular side of the CAM using these grouping techniques are programmed into both sides of the CAM. During packet routing, techniques similar to the grouping techniques that populated the CAM are used to determine which of the two sides of the CAM is to be searched.

A method and apparatus for input data selection for content addressable memory. In one embodiment, the apparatus includes an array of CAM cells, a select circuit adapted to generate a plurality of select signals each indicative of a segment of input data provided to the CAM apparatus, and switch circuitry including a plurality of programmable switch circuits each programmable to output a respective bit of the input data as a comparand bit for the array of CAM cells in response to one of the select signals.

A system and method provide for efficient classification of long strings of data, such as network messages. The system, which may be a classification engine for use in a network device, is configured to include one or more stages having one or more banks of ternary content addressable memories (TCAMs). The TCAM banks of each stage are organized into one or more groups and each group processes the network messages for a different set of the network device's ports. The system further includes at least one memory resource that is shared by the TCAM banks of all groups. That is, the parallel banks of TCAMs operate in a distributed fashion while the shared memory resource operates in a centralized fashion. Accordingly, the system can process network messages at high speed while minimizing the number of required components.

A multi-stage (e.g., two-stage) packet-based lookup process using a Ternary Content Addressable Memory (TCAM) divided into partitions. The result of a first stage lookup is used to selectively search one of a plurality of TCAM partitions during the second stage. A subset of destination address bits may be used in the first stage to hash to a selected partition for the second stage. Alternatively, a partitioning algorithm segments a routing trie into partitions, and then, either a separate, small TCAM or one of the partitions is used in the first stage to map a prefix of the destination address to one of the TCAM partitions for use in the second stage. The “trie-based” algorithms may advantageously partition the trie such that each second stage partition comprises a substantially contiguous sequence of routing prefixes in a post-order traversal of the routing trie, together with one or more covering prefixes thereof.

A programmable finite state machine (FSM) includes, in part, first and second memories, and a selection circuit coupled to each of the memories. Upon receiving a (k+m)-bit word representative of the k-bit input symbol and the m-bit current state, the first memory supplies one ore more matching transition rules stored therein. The selection circuit selects the most specific of the supplied rules. The transition rules are stored in the first memory in a ranking order of generality. The second memory receives the selected transition rule and supplies the next state of the FSM. The first memory may be a ternary content addressable memory and the second memory may be a static random access memory. The contents of both the content addressable memory and the static random memory is determined by an algorithm which minimizes the number of terms required to represent the next-state transition functions.

A method of managing rule entries of a Ternary Content Addressable Memory (TCAM) in a routing system includes: creating a hash table having a hash key corresponding to each entry; creating a single linked list for linking nodes, the single linked list using the entry of the hash table as a head node and including rule IDs and sequence IDs assigned according to a rule input order; and a double linked list having an independent head node, the double linked list bidirectionally linking the nodes constituting the single linked list according to an order of the sequence IDs. Thus, the packet classifying / filtering rule can be easily added to the TCAM or deleted from the TCAM only with minimal information. Also, the sequence ID reassignment process, required for storing as many rules in the TCAM as possible according to the priority of the rules, is performed when a certain time elapses following rule addition or deletion, thereby reducing a latency that may be caused upon setting the packet classifying / filtering rule.

The invention discloses a low-power ternary CAM by utilizing four encoded comparand datalines, C0, C1, C2, and C3 in a twin ternary cell. The twin ternary cell is a composite of two ternary CAM bits. The two binary CAM bits are coded so that only one of four comparand datalines is toggled during a compare operation. The encoded data is stored and used for comparison. In one embodiment, the four possible states for the 2 bit comparands are coded as 0001, 0010, 0100, and 1000.

A method of handling a datagram in a network device is disclosed. The steps include receiving a datagram, with the datagram having multiple field values, at a port of a network device, parsing the received datagram to obtain the field values, applying the parsed field values to a Ternary Content Addressable Memory (TCAM), determining matches between the parsed field values and predetermined criteria in the TCAM, indexing into a policy table based on the determined matches to obtain an action entry and taking an action based on the obtained action entry.

The invention provides a method and a system for realizing Openflow multi-stage flow tables on the basis of a ternary content addressable memory (TCAM). The method comprises the following steps of: S1, dividing a TCAM table maintained on an Openflow switch into multiple logical flow tables; and S2, setting the matched domain type for each logical flow table. The TCAM table is divided into multiple logical flow tables and the matched field length of each flow table comprises multiple forms, so that storage items of the TCAM table are effectively increased, different application requirements are met and the manufacturing cost of the Openflow switch is effectively reduced.

Methods, systems, and computer readable storage medium embodiments for configuring a lookup table for a network device are disclosed. Aspects in these embodiments include generating a decision tree based upon bit representations of respective data entries from a plurality of data entries where one or more of the plurality of data entries are represented at respective nodes of the decision tree, storing a first bit pattern corresponding to a selected node from the decision tree in a content addressable memory (CAM) at a location associated with an index, and storing one or more second bit patterns at an address in a second memory. The one or more second hit patterns correspond to the one or more data entries represented at the selected node, and the address is associated with the index. Embodiments also include searching a lookup table in a network device.

A hash-CAM (H-CAM) which may work with a controller and a memory containing a database of either search values and associate content or associate content by itself The H-CAM includes at least one set of paired hash units and CAM units and at least one logic unit. The CAM units hold values known to cause hash collisions in the respectively paired hash units, and the logic unit prioritizes the hash and CAM unit outputs to a single address value usable to access the memory and obtain a search result at the controller that is not the result of a hash collision. The H-CAM may optionally include a search data storage to store the search values, so that they need not be stored in the memory, and a comparator to determine and handle newly determined hash collisions.

A method for writing a magnetic random access memory-based ternary content addressable memory cell comprising a first magnetic tunnel junction being formed from a storage layer, a sense layer having a magnetization direction adjustable relative to the magnetization of the storage layer, and an insulating layer between the storage and sense layers; a sense line coupled with the storage layer; a first field line and a second field line, and the first field line being orthogonal to the second field line; comprising: providing a first write data to said storage layer via the second field line to store a first stored data with a high or low logic state; characterized in that, the method further comprises providing the first write data to said storage layer via the first field line to store the first stored data with a masked logic state.

A present invention provides a system and method for avoiding memory hazards in a multi-threaded CPU which shares an L-1 data cache. The system includes a CPU and an AACAM. The AACAM is capable of copying memory addresses from the two or more threads being processed by the CPU. The method provides for comparing the AACAM memory address with the active threads to avoid memory hazards by thread switching before the memory hazard occurs.

Lookup techniques are described, which can achieve improvements in energy efficiency, speed, and cost, of IP address lookup, for example, in devices and systems employing ternary content addressable memory (TCAM). The disclosed subject matter describes dividing a route table into several sub-tries with disjoint range boundaries. In addition, the disclosed subject matter describes storing sub-tries of a route table between a TCAM and a faster and less costly memory. The disclosed details enable various refinements and modifications according to system design and tradeoff considerations.

A memory system including a content addressable memory (CAM) array and a non-CAM array. The non-CAM array, which may share word lines with the CAM array, stores one or more error detection bits associated with each row of the CAM array. A state machine reads entries of the CAM array and corresponding error detection bits of the non-CAM array during idle cycles of the CAM array. Error detection logic identifies errors in the entries read from CAM array (using the retrieved error detection bits). If these errors are correctable, the error detection logic corrects the entry, and writes the corrected entry back to the CAM array (an updated set of error detection bits are also written to the non-CAM array). If these errors are not correctable, an interrupt is generated, which causes correct data to be retrieved from a shadow copy of the CAM array.

The present disclosure concerns a magnetic random access memory-based ternary content addressable memory cell, comprising a first and second magnetic tunnel junction respectively connected to a first and second straps extending on each side of the first and second magnetic tunnel junctions, respectively; a first and second selection transistors, respectively connected to one extremity of the first and second straps; a first and second current lines; and a conductive line electrically connecting in series the first and second magnetic tunnel junctions at their ends opposed to the ones connecting the first and second straps. The cell disclosed herein has smaller size and can be advantageously used in memory devices having a high cell density array.

A content addressable memory (CAM) device, method, and method of generating entries for range matching are disclosed. A CAM device (800) according to one embodiment can include a pre-encoder (806) that encodes range bit values W into additional bits E. Additional bits E can indicate compression of range rules according to particular bit pairs. A CAM array (802) can include entries that store compressed range code values (RANGE) with corresponding additional bit values (ENC). Alternate embodiments can include pre-encoders that encode portions of range values (K1 to Ki) in a “one-hot” fashion. Corresponding CAM entries can include encoded value having sections that each represent increasingly finer divisions of a range space.

A lookup table including stored data, the lookup table including a Random Access Memory (RAM) for storing the data, wherein the RAM includes a plurality of windows; and a Ternary Content Addressable Memory (TCAM) for storing indices, each index pointing to the windows, and a method for performing a Longest Prefix Match (LPM) including organizing data in such a lookup table, searching according to a lookup key in the TCAM, receiving a match signal from the TCAM including an index pointing to one of the windows, and searching according to the lookup key in the pointed to window.