Browsing by Author "Huang, Nai-Lun"

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A Flexible Product Management System for the IPTV Service
(2012)
Yu, Jen-Chieh
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Huang, Nai-Lun
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Wu, Jung-Shyr
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電信工程研究所
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Institute of Communications Engineering
As the Internet Protocol Television (IPTV) technology advances, IPTV services and customers increase. To attract more customers to raise profits, IPTV service providers usually launch many kinds of sales plans at the same time. Each sales plan has its own billing processing program so that the service subscription events are properly charged. Traditionally, sales plans are packaged case by case and billing processing programs are designed individually. However, the labor cost and time requirement augment as the number of sales plans increases. Therefore, how to gain working efficiency is obviously an important issue. In this paper, we propose a product management system that systematizes the packaging and programming procedure. The system, developed in modules, is flexible in the sense that similar sales plans, e.g. the plan of buy 3 get 1 free and the plan of buy 4 get 2 free, can be packaged by the same module with different parameter assignment. Existing packaging modules are reusable and new packaging modules can be added when needed. With the product management system, IPTV service significantly.
A Pattern-Matching Scheme With High Throughput Performance and Low Memory Requirement
(2013-08-01)
Lee, Tsern-Huei
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Huang, Nai-Lun
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傳播研究所
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Institute of Communication Studies
Pattern-matching techniques have recently been applied to network security applications such as intrusion detection, virus protection, and spam filters. The widely used Aho-Corasick (AC) algorithm can simultaneously match multiple patterns while providing a worst-case performance guarantee. However, as transmission technologies improve, the AC algorithm cannot keep up with transmission speeds in high-speed networks. Moreover, it may require a huge amount of space to store a two-dimensional state transition table when the total length of patterns is large. In this paper, we present a pattern-matching architecture consisting of a stateful pre-filter and an AC-based verification engine. The stateful pre-filter is optimal in the sense that it is equivalent to utilizing all previous query results. In addition, the filter can be easily realized with bitmaps and simple bitwise-AND and shift operations. The size of the two-dimensional state transition table in our proposed architecture is proportional to the number of patterns, as opposed to the total length of patterns in previous designs. Our proposed architecture achieves a significant improvement in both throughput performance and memory usage.
An Efficient and Scalable Pattern Matching Scheme for Network Security Applications
(2008)
Lee, Tsern-Huei
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Huang, Nai-Lun
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電信工程研究所
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Institute of Communications Engineering
Because of its accuracy, pattern matching technique has recently been applied to Internet security applications such as intrusion detection/prevention, anti-virus, and anti-malware. Among various famous pattern matching algorithms, the Aho-Corasick (AC) can match multiple pattern strings simultaneously with worst-case performance guarantee and is adopted in both Clam AntiVirus (ClamAV) and Snort intrusion detection open sources. The AC algorithm is based on finite automaton which can be implemented straightforwardly with a two-dimensional state transition table. However, the memory requirement prohibits such an implementation when the total length of the pattern strings is large. The ClamAV implementation limits the depth of the finite automaton and combines with linked lists to reduce memory requirement. The banded-row format is adopted to compress the state transition table and used as an alternative pattern matching machine in Snort. In this paper we present a novel implementation which requires small memory space and achieves high throughput performance. Compared with the banded-row format, our proposed scheme achieves 39.7% reduction in memory requirement for 5,000 patterns randomly selected from ClamAV signatures. Besides, the processing time of our proposed scheme is, on the average, 83.9% of that of the banded-row format for scanning various types of files. Compared with the ClamAV implementation with the same 5,000 patterns and files, our proposed scheme requires slightly more memory space but achieves 80.6% reduction in processing time on the average.
An efficient pattern matching scheme in LZW compressed sequences
(2008-07-01)
Lee, Tsern-Huei
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Huang, Nai-Lun
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電信工程研究所
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Institute of Communications Engineering
Compressed pattern matching (CPM) is an emerging research field addressing the problem: given a compressed sequence and a pattern, process the sequence with minimal (or no) decompression to find the pattern occurrence(s) in the uncompressed sequence. It can be applied to detect malwares and confidential information leakage in compressed files directly. In this paper, we report our work of CPM in Lempel-Ziv-Welch (LZW) compressed sequences. We propose an efficient bitmap-based realization of the Amir-Benson-Farach algorithm. We also generalize the algorithm to find all pattern occurrences and report their absolute positions in the uncompressed sequence. Experiments are conducted to test the space requirements of our proposed generalization and two related CPM schemes which can also be realized with bitmaps. Results show that our proposed generalization requires the least amount of storage for moderate and long patterns. We also conduct experiments to compare the throughput performance of our proposed generalization with these two related CPM schemes and the decompress-then-search scheme. Results show that our proposed generalization outperforms the decompress-then-search scheme significantly. When scanning a file with pattern occurrences, our proposed generalization performs slightly better than the two related CPM schemes. The difference is significant when scanning a file with no pattern occurrence. Copyright (c) 2008 John Wiley & Sons, Ltd.
Solution of Skip Distance Constraint on Sub-linear Time String-matching Architecture
(2013)
Huang, Nai-Lun
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Lee, Tsern-Huei
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Tseng, Kuo-Kun
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交大名義發表
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National Chiao Tung University
Pre-filters are well-known techniques used to speed up string-matching process. The skip-based pre-filters make it possible to achieve sub-linear time complexity. However, they have a common constraint that their skip distances are bounded by the shortest keyword length. If the shortest keyword length is small, then this constraint will be a bottleneck problem in string-matching throughput. This paper provides a solution that the skip distance can be longer than the shortest keyword length. Also, a matching strategy based on the solution is proposed. This strategy can not only solve the bottleneck problem, but also reduce the operations in the sub-linear time string-matching procedure.