Implementation method of three-state content addressable memory and device

Abstract

The invention discloses an implementation method of a three-state content addressable memory, applied to a device comprising a traditional TCAM and a cache module. The method comprises the following steps: acquiring a corresponding key from a received message by the cache module; searching whether a record item matched with the key exists in the cache module or not; returning the record item matched with the key if the record item matched with the key exists in the cache module; and sending the key to the traditional TCAM to search for a matched item if the record item matched with the key does not exist in the cache module. The invention generates a searching cache in a TCAM chip according to a searching key to solve the problems occurring in the prior TCAM.

Description

Technical field [0001] The present invention relates to the field of communication technology, in particular to a method and device for implementing a three-state content addressable memory. Background technique [0002] CAM (Content Addressable Memory, content addressable memory) is a hardware chip dedicated to table lookup operations. Compared with other algorithm-based solutions, CAM has excellent performance and more scalability. High-speed three-state CAM, such as TCAM (Ternary ContentAddressable Memory, three-state content addressable memory) allows the bit field to be masked in three ways: 0, 1 or X (ignored) (hence the name three-state). Determine the longest prefix match. The high-speed performance of TCAM can also be used for wire-speed forwarding of IP packets, and unlike software-based methods, the search performance of TCAM has nothing to do with the size and content of the routing table. [0003] TCAM is commonly used for high-end router routing search, ACL (Access...

AI Technical Summary

Problems solved by technology

[0004] The core of TCAM is to compare the input Key with the data and mask stored in TCAM by & (AND) operation. In order to achieve high search performance, it is necessary to compare the Key with all entries in TCAM in a short time. The number of rules increases, and the complexity of the comparison will be greatly increased

For example, TCAM stores 10,000 rules. In order to achieve the performance of 100M searches per second, it is necessary to compare the entire 10,000 rules within 10 ns, which is very difficult.

In addition, due to the large amount of logic resources occupied, it is difficult to achieve high capacity on a single chip under the existing technical conditions, resulting in increased cost and complicated implementation.

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