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An optimized Ternary CAM concept is introduced for the hardware search engines in high-speed Internet routers. Our design employs + 1 RAM bits to store a word of size , whereas a conventional TCAM needs 2 RAM bits for the same word size. Based on this concept an 8-bit cluster is designed out of 9 SRAM bits, used as the basic building block of our Prefix-CAM (PCAM) structure. Four such clusters merge to store a 32-bit IPv4 prefix, thus, configuring a PCAM suitable for Internet packet forwarding. This PCAM module employs 48% less SRAM cells and a total of 22% less transistors plus 50% less address decode interconnects compared to a conventional TCAM, for equal storage size and equal functionality. We show that PCAM can be employed for multifield packet classification. Other factors, such as lookup speed and power dissipation, are not adversely affected.Index Terms-Forwarding engine, packet classification, prefix-CAM, route lookup table, ternary content addressable memory.

Abstract-An optimized Ternary CAM concept is introduced for application in the longest prefix matching tasks of the Internet search engines. It employs w · 1 RAM bits for a word of size w.A conventional TCAM needs 2w RAM bits for the same word size. Based on this concept an 8 bit Prefix-CAM cluster is designed out of 9 SRAM bits, four of which merge to store a 32-bit IPv4 prefix. A complete Prefix-CAM module employs 22% less transistors than a conventional TCAM, for equal storage size and equal functionality. We confirm the 22% area saving by implementing the layouts for Prefix-CAM and TCAM words. Our design also reduces interconnect area by reducing address decode lines.

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