• Journal of KIISE:Information Networking
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• v.35 no.1
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• pp.91-97
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• 2008

In order to get a desired service in such environments, we need a service discovery method for discovering a device providing that service. In this paper, we propose a service discovery protocol which is based on DHTs (Distributed Hash Tables) to solve these problems. Our protocol is scalable since it does not require a central lookup server and does not rely on multicast or flooding. Simulation results show that our protocol is scalable and outperforms existing service discovery protocols.

• Review of KIISC
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• v.15 no.6
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• pp.60-67
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• 2005

올 9월 NGN2005에서는 2003년을 기점으로 하여 인터넷에서 가장 많은 트래픽을 차지하는 서비스가 P2P(Peer-to-Peer) 서비스라는 통계를 발표하였다. 실제로, 현재 수많은 사용자가 P2P 서비스를 이용하고 있으며 다양한 P2P 응용 및 구조에 대한 연구가 다소 활발히 진행되고 있는 상황이다. 최근에는 P2P 파일공유 응용분야에서 DHT(Distributed Hash Table) 기반의 오버레이 네트워크를 활용하고자 하는 일부 연구도 진행되고 있다. 이와 관련하여 본 고 에서는 DHT 기반 P2P 오버레이 네트워크를 구축하기 위한 기존의 방식들을 소개하고, 이에 대한 보안 위협을 분석하고자 한다.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.45 no.12
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• pp.58-65
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• 2008

This paper presents a new geographic distributed hash table (GDHT) for MANETs or Mesh networks, where virtual geographic protocol is used. In previous wort GDHT is applied to a network scenario based on two dimensional Cartesian coordinate system. Further, logical data space is supposed to be uniformly distributed. However, mobile node distribution in a network using virtual geographic routing is not matched to data distribution in GDHT. Therefore, if we apply previous GDHT to a virtual geographic routing network, lots of DHT data are probably located at boundary nodes of the network or specific nodes, resulting in long average-delay to discover resource (or service). Additionally, in BVR(Beacon Vector Routing) or LCR(Logical Coordinate Routing), because there is correlation between coordinate elements, we cannot use normal hash function. For this reason, we propose to use "geographic hash function" for GDHT that matches data distribution to node distribution and considers correlation between coordinate elements. We also show that the proposed scheme improves resource discovery efficiently.

• Journal of KIISE:Information Networking
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• v.36 no.2
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• pp.80-89
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• 2009

A DHT(Distributed Hash Table) based P2P is a method that compensates disadvantages of the existing unstructured P2P method. If a DHT algorithm is used, it can do fast data search and maintain search efficiency independent of the number of peers. The peers in a DHT method send messages periodically to keep the routing table updated. In a mobile environment, the peers in a DHT method should send messages more frequently to keep the routing table updated and reduce the failure of requests. However this results in increasing the overall network traffic. In this paper, we propose a method to reduce the update load of a routing table in the existing DHT by updating it in a reactive way. In the proposed reactive method, a routing table is updated only if a data request is coming whereas it is updated periodically in the existing proactive method. We perform experiments using Chord simulator(I3) made by UC Berkely. The experimental results show the performance improvement of the proposed method compared to the existing method.

• Journal of the Korea Society of Computer and Information
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• v.17 no.12
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• pp.111-120
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• 2012

As the P2P System is a distributed system that shares resources of nodes that participate in the system, all the nodes serve as a role of server and client. Currently, although systematic, structured P2P systems such as Chord, Pastry, and Tapestry were suggested based on the distributed hash table, these systems are limited to $log_2N$ for performance efficiency. For this enhanced performance efficiency limited, the article herein suggests group routing algorithm. The suggested algorithm is a node-to-group routing algorithm which divides circular address space into groups and uses a concept of pointer representing each group, which is an algorithm where routing is performed based on pointer. To evaluate algorithm performance, a comparative analysis was conducted on average hops, routing table size, and delayed transmission for chord and routing, a signature algorithm in P2P systems. Therefore, enhanced performance is verified for comparative items from the simulation results.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.11 no.8
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• pp.1486-1492
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• 2007

Searching distributed resources efficiently is very important in distributed computing environments like P2P. But distributed resource searching may have system overheads and take a lot of time in proportion to the searching number, because distributed resource searching has to circuit many peers for searching information. In this paper, we design a proxy peer algorithm based on DHT(Distributed Hash Table) for efficient distributed resource searching in JXTA network environments. By containing the rendezvous information in proxy peer and searching a rendezvous peer firstly which has higher hit ratio, we can reduce the searching number and minimize system overheads.

• The KIPS Transactions:PartC
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• v.16C no.4
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• pp.449-460
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• 2009

The signature hashing algorithm[9] provides the fast pattern matching speed for network IPS(Intrusion Prevention System) using the hash table. It selects 2 bytes from all signature rules and links to the hash table by the hash value. It has an advantage of performance improvement because it reduces the number of inspecting rules in the pattern matching. However it has a disadvantage of performance drop if the number of rules with the same hash value increases when the number of rules are large and the corelation among rules is strong. In this paper, we propose a method to make all rules distributed evenly to the hash table independent of the number of rules and corelation among rules for overcoming the disadvantage of the signature hashing algorithm. In the proposed method, it checks whether or not there is an already assigned rule linked to the same hash value before a new rule is linked to a hash value in the hash table. If there is no assigned rule, the new rule is linked to the hash value. Otherwise, the proposed method recalculate a hash value to put it in other position. We implemented the proposed method in a PC with a Linux module and performed experiments using Iperf as a network performance measurement tool. The signature hashing method shows performance drop if the number of rules with the same hash value increases when the number of rules are large and the corelation among rules is strong, but the proposed method shows no performance drop independent of the number of rules and corelation among rules.

• Journal of Industrial Technology
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• v.26 no.B
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• pp.199-206
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• 2006

Internet telephony provides voice communication services with added flexibility for multimedia extension at a lower cost compared to traditional telephone systems. We implemented an internet telephony system as an overlay network without a centralized server, using a distributed hash table (DHT). Compared to the current server-based internet telephony system, our system is fault-tolerant, scalable, and can be flexible extended to various services and advanced to integrated service. To demonstrate the high flexibility of our DHT-based internet telephony system, we made our system cooperate with web servers. Web users can check up others' online stales and establish voice communication sessions to online users at a mouse click. This technology can be applied to more complex services such as multimedia messaging or video conference service.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• v.9 no.1
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• pp.175-178
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• 2005

인터넷 상의 불특정 다수의 컴퓨팅 자원을 연계하여 오버레이 네트워크를 구성하여 새로운 컴퓨팅 인프라를 구성하려는 분산 해쉬 테이블 (Distributed Hash Table)방식의 Peer-to-Peer(P2P) 네트워크 관련 연구가 진행되고 있다. DHT 방식의 P2P네트워크는 자원의 복제 및 공유하여 컴퓨팅 시스템 전반에 걸친 신뢰성과 결함 감내 능력을 향상시키는 장점이 있는 반면에 하부 네트워크 정보를 무시하기 때문에 전체 시스템 구성 및 메시지 전송에 있어 실제적인 성능상의 문제점을 드러낸다. 이 논문에서는 하부 네트워크의 구성 정보를 이용하여 DHT 기반의 P2P 네트워크의 메시지 전송 방식의 효율을 높이는 방법을 소개한다.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• v.9 no.2
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• pp.150-152
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• 2005

인터넷 상의 컴퓨팅 자원을 오버레이 네트워크를 구성하여 새로운 컴퓨팅 인프라를 구성하려는 연구가 분산 해쉬 테이블 (Distributed Hash Table) 방식의 Peer-to-Peer(P2P) 네트워크로 실현되고 있다. DHT 방식의 P2P 네트워크는 자원의 복제 및 공유하여 컴퓨팅 시스템 전반에 걸친 신뢰성과 결함감내 능력을 향상시키고 Exactly Matching Query에 장점이 있는 반면에 다중키 질의, 계층 질의 및 구간 질의와 같은 복합 질의(Rich Query) 제원에 문제점을 드러낸다. 이 논문에서는 DHT 기반의 P2P 네트워크에서 Rich Query 를 지원하기 위한 방법을 소개한다.