• Proceedings of the Korea Information Processing Society Conference
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• 2004.11a
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• pp.773-776
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• 2004

IPv6 프리픽스를 자동으로 할당 받기 위한 메커니즘으로 IETF 워킹그룹을 중심으로 DHCPv6 프리픽스 옵션을 이용한 방식과, APD 기술을 이용한 방식으로 나눌 수 있다. 본 고에서는 IPv6 네트워크 환경에서 프리픽스 할당을 지원하는 싱글홉 기반의 DHCPv6 프리픽스 옵션을 살펴보고 멀티홉환경에서 이를 지원하기 위한 요구사항 및 프리픽스 할당 메커니즘을 제안하고자 한다.

• Electronics and Telecommunications Trends
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• v.19 no.1 s.85
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• pp.43-51
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• 2004

IPv6 프리픽스를 자동으로 할당 받기 위한 메커니즘으로 IETF 워킹그룹을 중심으로 DHCPv6 프리픽스 옵션을 이용한 방식과, APD 기술을 이용한 방식으로 나눌 수 있다. 본 고에서는 IPv6 네트워크 환경에서 라우터의 프리픽스 할당 및 플러그 앤 플레이 기능을 지원하는 DHCPv6 프리픽스 옵션을 이용한 기술을 중심으로 현재 표준화 동향 및 프로토콜 동작과정에 대해서 살펴보고자 한다.

• Journal of KIISE:Information Networking
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• v.32 no.4
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• pp.543-550
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• 2005

Demand for better services in the Internet has been increasing due to the rapid growth of the Internet, and hence next generation routers are required to perform intelligent packet classification. For a given classifier defining packet attributes or contents, packet classification is the process of identifying the highest priority rule to which a packet conforms. A notable characteristic of real classifiers is that a packet matches only a small number of distinct source-destination prefix pairs. Therefore, a lot of schemes have been proposed to filter rules based on source and destination prefix pairs. However, most of the schemes are based on sequential one-dimensional searches using trio which requires huge memory. In this paper, we proposea memory-efficient two-dimensional search scheme using source and destination prefix pairs. By constructing binary prefix tree, source prefix search and destination prefix search are simultaneously performed in a binary tree. Moreover, the proposed two-dimensional binary prefix tree does not include any empty internal nodes, and hence memory waste of previous trio-based structures is completely eliminated.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.16 no.11
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• pp.7456-7462
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• 2015

This paper proposes a spectral efficient space-frequency(SF) block coded single carrier-frequency division multiple access(SC-FDMA) transmission system in a relaying multi-path shadow area. The cyclic prefix(CP) is not used in the proposed system in order to prevent a loss of spectral efficiency due to the use of CP. The destruction of channel cyclicity due to the lack of CP is recovered at the receivers of relays and a destination station. Simulation results show that the performance of the proposed system without CP is almost same as that of the conventional system with full CP, thus increasing the spectral efficiency.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.33 no.5B
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• pp.285-295
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• 2008

Internet routers perform packet forwarding which determines a next hop for each incoming packet using the packet's destination IP address. IP address lookup becomes one of the major challenges because it should be performed in wire-speed for every incoming packet under the circumstance of the advancement in link technologies and the growth of the number of the Internet users. Many binary search algorithms have been proposed for fast IP address lookup. However, tree-based binary search algorithms are usually unbalanced, and they do not provide very good search performance. Even for binary search algorithms providing balanced search, they have drawbacks requiring prefix duplication. In this paper, a new binary search algorithm which provides the balanced binary search and the number of its entries is much less than the number of original prefixes. This is possible because of composing the binary search tree only with disjoint prefixes of the prefix set. Each node has a prefix vector that has the prefix nesting information. The number of memory accesses of the proposed algorithm becomes much less than that of prior binary search algorithms, and hence its performance for IP address lookup is considerably improved.

• Journal of KIISE:Databases
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• v.36 no.2
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• pp.84-98
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• 2009

Various algorithms and architectures for IP address lookup have been studied to improve forwarding performance in the Internet routers. Previous IP address lookup architecture using Bloom filter requires a separate Bloom filter as well as a separate hash table in each prefix length, and hence it is not efficient in implementation complexity. To reduce the number of hash tables, it applies controlled prefix expansion, but prefix duplication is inevitable in the controlled prefix expansion. Previous parallel multiple-hashing architecture shows very good search performance since it performs parallel search on tables constructed in each prefix length. However, it also has high implementation complexity because of the parallel search structure. In this paper, we propose a new IP address lookup architecture using all-length Bloom filter and all-length multiple hash table, in which various length prefixes are accomodated in a single Bloom filter and a single multiple hash table. Hence the proposed architecture is very good in terms of implementation complexity as well as search performance. Simulation results using actual backbone routing tables which have $15000{\sim}220000$ prefixes show that the proposed architecture requires 1.04-1.17 memory accesses in average for an IP address lookup.

• Journal of KIISE:Databases
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• v.36 no.6
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• pp.455-465
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• 2009

Suffix trees are widely used in similar sequence matching for DNA. They have several problems such as time consuming, large space usages of disks and memories and data skew, since DNA sequences are very large and do not fit in the main memory. Thus, in the paper, we present a space efficient indexing method called SENoM, allowing us to build trees without merging phases for the partitioned sub trees. The proposed method is constructed in two phases. In the first phase, we partition the suffixes of the input string based on a common variable-length prefix till the number of suffixes is smaller than a threshold. In the second phase, we construct a sub tree based on the disk using the suffix sets, and then write it to the disk. The proposed method, SENoM eliminates complex merging phases. We show experimentally that proposed method is effective as bellows. SENoM reduces the disk usage less than 35% and reduces the memory usage less than 20% compared with TRELLIS algorithm. SENoM is available to query efficiently using the prefix tree even when the length of query sequence is large.

• Journal of Korea Society of Industrial Information Systems
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• v.20 no.6
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• pp.1-10
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• 2015

In this paper, we propose a spectral efficient orthogonal frequency division multiple access(OFDMA) transmission system using multiple relays for a shadow area. The performance of the proposed OFDMA system in a shadow area can be improved by applying space-frequency(SF) block code over relaying multi-path channels. A simple channel cyclicity restoration method is also added in the proposed OFDMA system without cyclic prefix(CP) to recover the destruction of channel cyclicity due to the lack of CP. Simulation results show that the proposed OFDMA system without CP is almost same as that of the conventional OFDMA system with sufficient CP, which increases the spectral efficiency of the system.

• Journal of the Korea Society of Computer and Information
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• v.15 no.12
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• pp.93-100
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• 2010

In this paper, we propose a technique which makes it faster to delete prefixes in an IP address lookup architecture based on parallel TCAMs. In previous deletion schemes, more than one memory movement is needed for the prefix ordering and keeping the available memory space consecutive. For deletion, our scheme stores the address of the deleted prefix in a stack implemented by SRAM instead of actual movement in TCAM. Since SRAM has very short latency compared to TCAM, the proposed scheme can accomplish fast updating. From the experiment with the real forwarding table and update trace, we evaluate the performance of our scheme in terms of the memory access time for the prefix insertion and deletion. The experiment result also shows good performance with considerably small size of stack.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.31 no.2B
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• pp.71-79
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• 2006

Address lookup is an essential function in the Internet routers, and it determines overall router performance. In this paper, we have thoroughly investigated the binary-search-based address lookup algorithms and proposed a new algorithm based on binary search on prefix lengths. Most of the existing binary search schemes perform binary search on prefix values, and hence the lookup speed is proportional to the length of prefixes or the log function of the number of prefixes. The previous algorithm based on binary search on prefix lengths has superior lookup performance than others. However, the algorithm requires very complicated pre-computation of markers and best matching prefixes in internal nodes since naive binary search is not possible in their scheme. This complicated pre-computation makes the composition of the routing table and incremental update very difficult. By using leaf-pushing, the proposed algorithm in this paper removes the complicated pre-computation of the Previous work in performing the binary search on prefix lengths. The performance evaluation results show that the proposed scheme has very good performance in lookup speed compared with previous works.