Extended TCAM for Adopting Range and Negation Rules in Packet Classification

General packet filtering systems using TCAM have some limitations such as inefficient searching the range and negation rules. To improve these problems, we propose the extended TCAM architecture and the efficient scheme for converting the rules into smaller TCAM entries. The proposed TCAM architecture has additional RC blocks for negation rules and Gray code generation block for range rules. The converting algorithm takes advantage of the Gray code's symmetric characteristics to reduce the number of TCAM entries for range rules and utilize the functionality of RC blocks for negation rules. Functional tests and performance analysis of the proposed TCAM are conducted by using a FPGA design tool and the simulation results with the SNORT rules show that the proposed TCAM architecture and algorithm reduce 93% of TCAM entries at the expense of little hardware overhead of 2 bits per a memory word