• Title/Summary/Keyword: Prefix grouping

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A Parallel Multiple Hashing Architecture Using Prefix Grouping for IP Address Lookup (프리픽스 그룹화를 이용한 병렬 복수 해슁 IP 주소 검색 구조)

  • Kim Hye ran;Jung Yeo jin;Yim Chang boon;Lim Hye sook
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.30 no.3B
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    • pp.65-71
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    • 2005
  • The primary function of the Internet routers is to forward incoming packets toward their final destinations. IP address lookup is one of the most important functions in evaluating router performance since IP address lookup should be performed in wire-speed for the hundred-millions of incoming packets per second. With CIDR, the IP prefixes of routing table have arbitrary lengths, and hence address lookup by exact match is no longer valid. As a result, when packets arrive, routers compare the destination IP addresses of input packets with all prefixes in its routing table and determine the most specific entry among matching entries, and this is called the longest prefix matching. In this paper, based on parallel multiple hashing and prefix grouping, we have proposed a hardware architecture which performs an address lookup with a single memory access.

A High-speed IP Address Lookup Architecture using Adaptive Multiple Hashing and Prefix Grouping (적응적인 복수 해슁과 프리픽스그룹화를 이용한 고속 IP 주소 검색 구조)

  • Park Hyun-Tae;Moon Byung-In;Kang Sung-Ho
    • Journal of the Institute of Electronics Engineers of Korea TC
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    • v.43 no.5 s.347
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    • pp.137-146
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    • 2006
  • IP address lookup has become a major bottleneck of packet forwarding and a critical issue for high-speed networking techniques in routers. In this paper, we propose an efficient high-speed IP address lookup scheme using adaptive multiple hashing and prefix grouping. According to our analysis results based on routing data distributions, we grouped prefix lengths and selected the number of hash functions in each group adaptively. As a result, we can reduce collisions caused by hashing. Accordingly, a forwarding table of our scheme has good memory efficiency, and thus is organized with the proper number of memory modules. Also, the proposed scheme has the fast building and searching mechanisms to develop the forwarding table only during a single memory access.

An Algorithm for Computing Range-Groupby Queries (영역-그룹화 질의 계산 알고리즘)

  • Lee, Yeong-Gu;Mun, Yang-Se;Hwang, Gyu-Yeong
    • Journal of KIISE:Databases
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    • v.29 no.4
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    • pp.247-261
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    • 2002
  • Aggregation is an important operation that affects the performance of OLAP systems. In this paper we define a new class of aggregation queries, called range-groupby queries, and present a method for processing them. A range-groupby query is defined as a query that, for an arbitrarily specified region of an n-dimensional cube, computes aggregations for each combination of values of the grouping attributes. Range-groupby queries are used very frequently in analyzing information in MOLAP since they allow us to summarize various trends in an arbitrarily specified subregion of the domain space. In MOLAP applications, in order to improve the performance of query processing, a method of maintaining precomputed aggregation results, called the prefix-sum array, is widely used. For the case of range-groupby queries, however, maintaining precomputed aggregation results for each combination of the grouping attributes incurs enormous storage overhead. Here, we propose a fast algorithm that can compute range-groupby queries with minimal storage overhead. Our algorithm maintains only one prefix-sum away and still effectively processes range-groupby queries for all possible combinations of the grouping attributes. Compared with the method that maintains a prefix-sum array for each combination of the grouping attributes in an n-dimensional cube, our algorithm reduces the space overhead by (equation omitted), while accessing a similar number of cells.

Iceberg Query Evaluation Technical Using a Cuboid Prefix Tree (큐보이드 전위트리를 이용한 빙산질의 처리)

  • Han, Sang-Gil;Yang, Woo-Sock;Lee, Won-Suk
    • Journal of KIISE:Databases
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    • v.36 no.3
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    • pp.226-234
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    • 2009
  • A data stream is a massive unbounded sequence of data elements continuously generated at a rapid rate. Due to the characteristics of a data stream, it is impossible to save all the data elements of a data stream. Therefore it is necessary to define a new synopsis structure to store the summary information of a data stream. For this purpose, this paper proposes a cuboid prefix tree that can be effectively employed in evaluating an iceberg query over data streams. A cuboid prefix tree only stores those itemsets that consist of grouping attributes used in GROUP BY query. In addition, a cuboid prefix tree can compute multiple iceberg queries simultaneously by sharing their common sub-expressions. A cuboid prefix tree evaluates an iceberg query over an infinitely generated data stream while efficiently reducing memory usage and processing time, which is verified by a series of experiments.

A Grouping Technique for Synchronous Digital Duplexing Systems (동기식 디지털 이중화 시스템을 위한 그룹핑 기법)

  • Ko, Yo-Han;Park, Chang-Hwan;Park, Kyung-Won;Jeon, Won-Gi;Paik, Jong-Ho;Lee, Seok-Pil;Cho, Yong-Soo
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.34 no.4C
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    • pp.341-348
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    • 2009
  • In this paper, we propose a grouping technique for the SDD(Synchronous Digital Duplexing) based on OFDMA(Orthogonal Frequency Division Multiple Access). The SDD has advantages of increasing data efficiency and flexibility of resource since SDD can transmit uplink signals and downlink signals simultaneously by using mutual time information and mutual channel information, obtained during mutual ranging process. However, the SDD has a disadvantage of requiring additional CS to maintain orthogonality of OFDMA symbols when the sum of mutual time difference and mutual channel length between AP(access point) and SS(subscriber station) or among SSs are larger than CP length. In order to minimize the length of CS for the case of requiring additional CS in SDD, we proposes a grouping technique which controls transmit timing and receive timing of AP and SS in a cell by classifying them into groups. Performances of the proposed grouping technique are evaluated by computer simulation.

Longest First Binary Search on Prefix Length for IP Address Lookup (최장 길이 우선 검색에 기초한 프리픽스 길이에 따른 이진 IP 검색 구조)

  • Chu Ha-Neul;Lim Hye-Sook
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.31 no.8B
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    • pp.691-700
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    • 2006
  • Based on the destination IP address of incoming packets, the Internet routers determine next hops and forward packets toward final destinations through If address lookup. The bandwidth of communication links increases exponentially fast as well as the routing table size grows significant as the number of single host networks attached to the Internet increases. Since packets should be processed at wire-speed, the increased link speed reduces the processing time of a packet in routers, and hence more efficient and fast IP address lookup algorithms and architectures are required in the next generation routers. Most of the previous IP lookup schemes compare routing prefixes of shorter length first with a given input IP address. Since IP address lookup needs to find the most specific route of the given input, search continues until the longest matched prefix is found while it keeps remembering the current test matching prefix. In this paper, based on binary search on prefix length, we proposed a new IP address lookup algorithm which compares longer prefixes first. The proposed scheme is consisted of multiple tries with prefixes on leaves only. The trie composed of the longest prefixes is primarily searched whether there is a match with the given input. This processing is repeated for the trio of the next longer prefixes until there finds a match. Hence the proposed algorithm provides the fast search speed. The proposed algorithm also provides the incremental update of prefixes while the previous binary search on length scheme does not provide the incremental update because of pre-processing requirement. In this paper, we performed extensive simulations and showed the performance comparisons with related works.

A Global IPv6 Unicast Address Lookup Scheme Using Variable Multiple Hashing (가변적인 복수 해슁을 이용한 글로벌 IPv6 유니캐스트 주소 검색 구조)

  • Park Hyun-Tae;Moon Byung-In;Kang Sung-Ho
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.31 no.5B
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    • pp.378-389
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    • 2006
  • An IP address lookup scheme has become a critical issue increasingly for high-speed networking techniques due to the advent of IPv6 based on 128bit. In this paper, a novel global IPv6 unicast address lookup scheme is proposed for next generation internet routers. The proposed scheme perform a variable multiple hashing based on prefix grouping. Accordingly, it should not only minimize overflows with the proper number of memory modules, but also reduce a memory size required to organize forwarding tables. It has the fast building and searching mechanisms for forwarding tables during only a single memory access. Besides, it is easy to update forwarding tables incrementally. In the simulation using CERNET routing data as a 6bone test phase, we compared the proposed scheme with a similar scheme using a uniform multiple hashing. As a result, we verified that the number of overflows is reduced by 50% and the size of memory for forwarding tables is shrunken by 15% with 8 tables.