Efficient location of free spaces in TCAM to improve router performance

Abstract

SUMMARYA ternary content-addressable memory (TCAM) is a popular hardware device for performing fast IPaddress lookup. Because keeping all entries sorted in TCAM, we need move the entries for inserting a new entry. In this paper, we have presented a scheme for minimizing route update overheads in TCAM-based forwarding engines. Our optimizations are based on the hierarchy of prefixes in the routing table. The number of memory movement per update depends on the sequence of the new-inserted prefixes, instead of the initial prefixes in routing table. For the real route update traces, the average number of movements is less than 0.01. Further, when compared to an existing optimization algorithm, in the average case, our algorithm shows a 90% reduction in movement overheads.

An Efficient IP Lookup Architecture with Fast Update Using Single-Match TCAMs

“…Wu et al [5] presented an update algorithm based on the prefix level. A forwarding table is divided into several partitions according to the levels in a prefix search trie and the partitions are ordered by its level.…”

“…Then, the prefix 101* isn't disjoint with p 1 =10100*, p 2 =1011* and p 8 =10* which are in TCAM 0, TCAM 1 , and TCAM 5 , respectively. Consequently, available [0], available [1] and available [5] keep the false value. On the other hand, every prefix in TCAM 2, TCAM 3 , TCAM 4 and TCAM 6 is disjoint with the new prefix 101*.…”

“…If an 8-bit destination address 10100100 is given, then only TCAM 0 and TCAM 5 contain the matched prefixes p 1 =10100* and p 8 =10*, respectively. So, entry [0] and entry [5] are set by the location of p 1 in TCAM 0 and that of p 8 in TCAM 5 , respectively. Unless conventional TCAM 7 contains the matching prefix whose length is longer than 5 of p 1 's length, the algorithm in Fig.…”