Bit weaving: A non-prefix approach to compressing packet classifiers in TCAMs

Abstract

Abstract-Ternary Content Addressable Memories (TCAMs) have become the de facto standard in industry for fast packet classification. Unfortunately, TCAMs have limitations of small capacity, high power consumption, high heat generation, and high cost. The well-known range expansion problem exacerbates these limitations as each classifier rule typically has to be converted to multiple TCAM rules. One method for coping with these limitations is to use compression schemes to reduce the number of TCAM rules required to represent a classifier. Unfortunately, all existing compression schemes only produce prefix classifiers. Thus, they all miss the compression opportunities created by non-prefix ternary classifiers.In this paper, we propose bit weaving, the first non-prefix compression scheme. Bit weaving is based on the observation that TCAM entries that have the same decision and whose predicates differ by only one bit can be merged into one entry by replacing the bit in question with *. Bit weaving consists of two new techniques, bit swapping and bit merging, to first identify and then merge such rules together. The key advantages of bit weaving are that it runs fast, it is effective, and it is composable with other TCAM optimization methods as a pre/post-processing routine.We implemented bit weaving and conducted experiments on both real-world and synthetic packet classifiers. Our experimental results show the following: (i) bit weaving is an effective stand-alone compression technique (it achieves an average compression ratio of 23.6%) and (ii) bit weaving finds compression opportunities that other methods miss. Specifically, bit weaving improves the prior TCAM optimization techniques of TCAM Razor and Topological Transformation by an average of 12.8% and 36.5%, respectively.

Optimizing rule placement in software-defined networks for energy-aware routing

“…Another approach is to compress policies on a single switch. For example, the authors in [24,25,26] have proposed algorithms to reduce the number of rules needed to realize policies on a single switch. To the best of our knowledge, the closest papers to our work are from [16,17].…”

“…However, we note that the current algorithms can find optimal solution of energy consumption (or close-to-optimal if it is heuristic) in case we consider the default rule but not the wildcard. If the rule space is very limited and we can not find feasible solution, we can apply the work in "compressing policy on a single switch" [24,25,26] as a post-processing step to reduce more the routing table size. This post-processing step will be integrated into our algorithms in the future work.…”

Flowtable-Free Routing for Data Center Networks: A Software-Defined Approach

“…Moreover, TCAMs use ternary format for rules storage, which causes the well-know range expansion problem. That is, a flow rule leads to a large number of TCAM entries [5]. Therefore, cutting the sizes of flowtables is an essential issue.…”

Access Control List Provides Security in Network

“…In the general problem of access control list compression given an access control list g, produce an additional access control list g' that is semantically corresponding to g but has the smallest possible number of rules and this was called an access control list compression [10]. Five versions of compression of access control list that be at variance only in the set-up of field constraints of the output access control list were focussed as: range access control list compression where constraints of field are specific by a range of integers; prefix access control list compression where constraints of field are specified by means of a string prefix; ternary access control list compression, where constraints of fields are specified by means of a ternary string; range-prefix access control list compression where several constraints of field are precise by ranges and the lasting field constraints are particular by means of prefix strings and range-ternary access control list compression where field constraints of field are particular by means of ranges and the enduring field constraints are specified by ternary strings.…”