• Journal of KIISE:Information Networking
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• v.36 no.1
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• pp.57-67
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• 2009

Packet forwarding in the Internet routers is to find out the longest prefix that matches the destination address of an input packet and to forward the input packet to the output port designated by the longest matched prefix. The IP address lookup is the key of the packet forwarding, and it is required to have efficient data structures and search algorithms to provide the high-speed lookup performance. In this paper, an efficient IP address lookup algorithm using binary search is investigated. Most of the existing binary search algorithms are not efficient in search performance since they do not provide a balanced search. The proposed binary search algorithm performs perfectly balanced binary search using switch pointers. The performance of the proposed algorithm is evaluated using actual backbone routing data and it is shown that the proposed algorithm provides very good search performance without increasing the memory amount storing the forwarding table. The proposed algorithm also provides very good scalability since it can be easily extended for multi-way search and for large forwarding tables

• Journal of KIISE:Information Networking
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• v.34 no.2
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• pp.88-99
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• 2007

P2P systems are distributed data sharing systems, and each node in them plays the role of client as well as server. There are several studies using Distributed Hash Table, such as Chord, CAN, Tapestry, Pastry, but these systems don't consider the physical latency, therefore they have a weakness of difficulty to guarantee stable performance. To improve this problem, we present the TP2P system. This system is a self-organizing hierarchical overlay system and it uses Chord routing mechanism for lookup data. This system is organized by several subnets, each subnet is organized by physically close nodes, and global network organized by all nodes. In each subnet, one node finds a data, it saves in a node in the subnet, therefore it has higher probability to reduce physical lookup latency than Chord system. And each node has global information of some nodes in its subnet, and it is used to lookup data, therefore the number of hops decrease about 25% as well as the physical lookup latecy are reduced.

• Journal of the Korean Society for information Management
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• v.23 no.3 s.61
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• pp.49-68
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• 2006

It is required to enhance the value of ISBN as a tool for book search, identification, browsing, and improve the accessability and search capability of library OPAC. Bookmarklet is a small size javascript which can be saved as URL in a web browser bookmark or web page hyperlink. Open source bookmarklet can extract ISBN from web pages and search a book from library OPAC using the ISBN, so it is recognized as a simple but powerful search tool. In foreign countries, commercial library system vendors, libraries, OCLC, etc. are providing bookmarklets which allow a user to search for library holdings and loan information in a real time while he/she is travelling in an online bookshop web page. Therefore, this paper compared and analyzed international bookmarklets application examples and proposed LibraryLookup service in which library OPAC and online bookshop can make use of the bookmarklets.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.29 no.11B
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• pp.911-919
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• 2004

IP address lookup is one of the essential functions on internet routers, and it determines overall router performance. The most important evaluation factor for software-based IP address lookup is the number of the worst case memory accesses. Binary prefix tree (BPT) scheme gives small number of worst case memory accesses among previous software-based schemes. However the tree structure of BPT is normally unbalanced. In this paper, we propose weighted binary prefix tree (WBP) scheme which generates nearly balanced tree, through combining the concept of weight to the BPT generation process. The proposed WBPT gives very small number of worst case memory accesses compared to the previous software-based schemes. Moreover the WBPT requires comparably small size of memory which can be fit within L2 cache for about 30,000 prefixes, and it is rather simple for prefix addition and deletion. Hence the proposed WBPT can be used for software-based If address lookup in practical routers.

• Journal of Korea Multimedia Society
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• v.9 no.2
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• pp.244-254
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• 2006

This paper presents an efficient hybrid technique to compact the trie indexing the huge forward table small enough to be stored into cache for speeding up IP lookup. It combines two techniques, an encoding scheme called bit-map and a controlled-prefix expanding scheme to replace slow memory search with few fast-memory accesses and computations. For compaction, the bit-map represents each index and child pointer with one bit respectively. For example, when one node denotes n bits, the bit-map gives a high compression rate by consumes $2^{n-1}$ bits for $2^n$ index and child link pointers branched out of the node. The controlled-prefix expanding scheme determines the number of address bits represented by all root node of each trie's level. At this time, controlled-prefix scheme use a dynamic programming technique to get a smallest trie memory size with given number of trie's level. This paper proposes standard that can choose suitable trie structure depending on memory size of system and the required IP lookup speed presenting optimal memory size and the lookup speed according to trie level number.

• 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.

• 제어로봇시스템학회:학술대회논문집
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• 2003.10a
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• pp.1088-1092
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• 2003

This paper presents a combined lookup table technique and PI-type controller. The purpose of the designed controller is applied to control the nonlinear system as thermal process. The proposed controller is easy and convenient to design based on a commercial controller. The performances of the proposed controller were studied using the thermal plant model under temperature control. The experimental results included demonstrate the good performance of the proposed controller.

• Proceedings of the IEEK Conference
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• 2000.11a
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• pp.85-88
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• 2000

In order to resolve problems according to the phase error in QPSK demodulator of the digital communication systems. The demodulator requires carrier recovery loop which searches for the frequency and phase of the carrier. In this paper the complexity of implementation is reduced by the reduction into half of the number of the multiplier in filter structure of the conventional carrier recovery loop, and as the drawback of NCO of the conventional carrier recovery loop wastes a amount of power for the structure of lookup table , We designed the structure of combinational logic without the lookup table. In the comparison with dynamic power of the proposed NCO, the power of NCO with the lookup table is 175㎼, NCO with the proposed structure is 24.65㎼. As the result, it is recognized that about one eight of loss power is reduced. In the simulation of carrier recovery loop designed QPSK demodulator, it is known that the carrier phase is compensated.

• Proceedings of the IEEK Conference
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• 2004.06b
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• pp.589-592
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• 2004

The CORDIC algorithm can be implemented very simple H/W, but needs a lot of latency to compute trigonometric function. The RA(Redundant Arithmetic) resolves this problem, but also has difficulty to determine the directions of micro-rotations. The pre-computed direction of micro-rotation algorithm relieves the RA of this matter. In this paper, we proposed the modified the pre-computed algorithm adopted with a table-lookup. Instead of reducing H/W complexity, its performance and calculation errors are improved.

• Proceedings of the Korea Information Processing Society Conference
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• 2001.10b
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• pp.1399-1402
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• 2001

네트워크가 발전하면서 무선 환경에서 각종 장치들을 연결하고자 하는 요구가 늘어나고 있다. 무선 장치들은 전력소모를 줄여야하기 때문에 보다 많은 기능을 탑재하는 데에 어려움이 따른다. 특히, 실행중에 다른 장치를 인식하고 환경설정하며 실행상태를 관찰하는 것은 많은 에너지를 필요로 하는 복잡한 작업일 수 있다. Jini 기술은 장치들을 자동으로 인식하고 설정하는 데에 있어 강력하면서도 단순한 Service Discovery Protocol을 포함하고 있다. 그러나 Jini는 유선 네트워크를 기준으로 개발되어졌기 때문에 무선, 특히 Ad-hoc 네트워크 환경에 적응하기 위해서는 각 요소들이 어떠한 중계도 없이 독립적으로 서로를 인식한 수 있도록 개선되어야 한다. Lookup Server가 작동을 멈추거나 룩업서비스를 받을 수 없는 지역에 있다면, 클라이언트는 서비스를 찾을 수 없고 서비스들도 새롭게 등록될 수 없다. 특히 이동성을 지닌 Ad-hoc 네트워크에서 룩업서비스의 존재는 보장받기 어렵다. 본 논문은 Jini를 기반으로 Ad-hoc 네트워크를 구축한 때 룩업서비스의 일부 기능을 클라이언트에게 분산시키고 다른 클라이언트와 정보를 공유한 수 있도록 개선된 Jini Discovery를 제안한다.