PCAM: a ternary CAM optimized for longest prefix matching tasks

Abstract

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.

Arranging multicast forwarding table in class sequence in ternary-cam for line-speed lookup

“…M in the figure is used to represent the total number of entries in the first class, and N is the total number of entries in the second class. As shown in the figure, all the M entries in the first class should be stored in lower address than that of the N entries in the second class, and there is no need to store entries of the Fig.3 Arranging entries in class sequence in the TCAM same class in any specific order, hence here the traditional fast updating problem for TCAMs [8,16,19] would no longer be a problem. Modification 2 Setting mask for multicast forwarding table in the TCAM at class level Here, we first describe the mask in TCAM in detail.…”

“…Firstly, we give the class definition of the multicast forwarding table. Secondly, based on the class definition, we give three modifications to the traditional TCAM based lookup engine [3,4,16] , so as to attain the object of using one search and a TCAM to get the correct lookup result.…”

A New Lookup Model for Multiple Flow Tables of Open Flow with Implementation and Optimization Considerations

“…TCAM is not the most appropriate solution for the lookup operation for all types of fields. In addition, due to power and cost reasons, TCAM is widely adopted for small-size routing tables [12,13].…”

A CAM/WTA-Based High Speed and Low Power Longest Prefix Matching Circuit Design

“…6 Eqs. (4) and (5), where Di, is the input bit-pattern, CM is mask signal for the current stage, and NM is the mask signal for next stage. MAXJ = Q1j +Q2j + .+Qj (3) Q =CM Din (4) NM =(Q+MAX) CM (5) Although the proposed CW-LPM search engine requires some extra hardware components, such as ELR and maskable WTA/MAX circuit, the required extra bit length of these components are only Flogn], where n is the bit length of the prefix data.…”

“…The processing costs and architectural implications make it difficult to achieve high-speed like OC-768 (Line-rate 40 Gb/s) or OC-3072 (Line-rate 160 Gb/s) routing at higher speeds when using software-based processing. Thus, some high-speed hardware-based solutions using Ternary-CAM (TCAM) have been presented to overcome these difficulties because the TCAM-based solution has the properties of simplicity and high performance [4].…”