• Journal of Communications and Networks
• /
• 제11권5호
• /
• pp.500-508
• /
• 2009

We have designed an algorithm for a problem in multicast communication. The problem is to construct a multicast tree while minimizing its cost, which is known to be NP-complete. Our algorithm, which employs new concepts defined as potential cost and spanning cost, generates a multicast tree more efficiently than the well-known heuristic called Takahashi and Matsuyama (TM) [1] in terms of tree cost. The time complexity of our algorithm is O($kn^2$) for an n-node network with k members in the multicast group and is comparable to the TM. Our empirical performance evaluation comparing the proposed algorithm with TM shows that the enhancement is up to 1.25%~4.23% for each best case.

• 한국경영과학회:학술대회논문집
• /
• 대한산업공학회/한국경영과학회 2002년도 춘계공동학술대회
• /
• pp.120-127
• /
• 2002

The multicasting is defined as the distribution of the same information stream from one to many nodes concurrently. There has been an intensive research effort to design protocols and construct multicast routing graphs for a single multicast group. However. there have been few researches about the relation between multiple and concurrent multicast groups. In this paper, the multiple multicast tree allocation algorithm to avoid congestion is proposed. The multicast group with different bandwidth requirement is also considered. A two-phase algorithm is proposed. The first phase is for basic search and the second phase for further improvement. The performance of the proposed algorithm is experimented with computational results. Computational results show that the proposed algorithm outperforms an existing algorithm.

• 산업공학
• /
• 제20권4호
• /
• pp.504-514
• /
• 2007

The multicast routing problem lies in the composition of a multicast routing tree including a source node and multiple destinations. There is a trade-off relationship between cost and delay, and the multicast routing problem of optimizing these two conditions at the same time is a difficult problem to solve and it belongs to a multi-objective optimization problem (MOOP). A multi-objective genetic algorithm (MOGA) is efficient to solve MOOP. A micro-genetic algorithm(${\mu}GA$) is a genetic algorithm with a very small population and a reinitialization process, and it is faster than a simple genetic algorithm (SGA). We propose a multi-objective micro-genetic algorithm (MO${\mu}GA$) that combines a MOGA and a ${\mu}GA$ to find optimal solutions (Pareto optimal solutions) of multicast routing problems. Computational results of a MO${\mu}GA$ show fast convergence and give better solutions for the same amount of computation than a MOGA.

• 한국컴퓨터정보학회논문지
• /
• 제8권3호
• /
• pp.150-155
• /
• 2003

멀티캐스트는 한 점에서 다수의 집단 구성원들에게 데이터를 전송하는 것으로 이는 멀티캐스트 트리를 구성하여 해결할 수 있다. 즉, 전체 네트워크를 몇 개의 클러스터로 분할한 후 클러스터 내부를 멀티캐스트 트리로 구성하여 해결할 수 있다. 본 논문에서는 클러스터링 방법을 사용하여 멀티캐스트 라우팅 비용을 줄이는 알고리즘을 제안한다. 멀티캐스트 트리는 최소비용 스타이너 트리로 구성할 수 있기 때문에 최소비용 스타이너 트리 문제를 해결하는 것이 중요하다. 따라서, 본 논문에서는 멀티캐스트 라우팅 문제의 해법으로 클러스터링 방법을 이용한 유전자 알고리즘을 제안한다.

• Journal of Information Processing Systems
• /
• 제13권3호
• /
• pp.546-558
• /
• 2017

The amount of multimedia traffic over the Internet has been increasing because of the development of networks and mobile devices. Accordingly, studies on multicast, which is used to provide efficient multimedia and video services, have been conducted. In particular, studies on centralized multicast tree construction have attracted attention with the advent of software-defined networking. Among the centralized multicast tree construction algorithms, the group Takahashi and Matsuyama (GTM) algorithm is the most commonly used in multiple multicast tree construction. However, the GTM algorithm considers only the network-cost overhead when constructing multicast trees; it does not consider the temporary service disruption that arises from a link change for users receiving an existing service. Therefore, in this study, we propose a multiple multicast tree construction algorithm that can reduce network cost while avoiding considerable degradation of service quality to users. This is accomplished by considering both network-cost and link-change overhead of users. Experimental results reveal that, compared to the GTM algorithm, the proposed algorithm significantly improves the user-experienced quality of service by substantially reducing the number of linkchanged users while only slightly adding to the network-cost overhead.

• 한국멀티미디어학회논문지
• /
• 제2권2호
• /
• pp.184-194
• /
• 1999

본 논문은 양방향 스위치(bidirectional switchs)를 가진 다단계 상호연결망(MIN, Multistage Interconn nection Network)에서 중첩된 목적지 노드로 다중 메시지를 전송할 때 야기되는 스위치간의 블럭킹(blocking) 을 최소화하기 위한 알고리즘을 제시한다. U~MIN(Unicast MIN) 알고리즘[4]에 의해 제시되었던 다중 전송 트리는 하나의 소스 노드로부터 여러 개의 목적지 노드로 메시지를 전송하는 단순한 멀티캐스트를 수행하는 데 있어서는 매우 유용하지만, 다중 멀티캐스트를 수행하는데 있어서는 섬각한 채널 경쟁을 야기한다. 따라서 간접통신망에서 동시에 같은 목적지 노드를 가진 멀티캐스트가 발생했을 때 기존의 U-MIN 알고리즘에서 발생하는 심각한 채널 경쟁을 최소화하기 위한 방법으로 본 논문에서는 SPU-MIN(Source Partitioned U Unicast MIN) 알고리즘에 의한 새로운 멀티캐스트 트리를 제시한다 본 논문에서의 메시지 전송 방법은 웹흘 라우팅 기법에 기반한 반전(turnaround) 라우팅 알고리즘을 이용한다.

• ETRI Journal
• /
• 제28권3호
• /
• pp.329-336
• /
• 2006

This paper investigates the problem of protecting multicast sessions in mesh wavelength-division multiplexing (WDM) networks against single link failures, for example, a fiber cut in optical networks. First, we study the two characteristics of multicast sessions in mesh WDM networks with sparse light splitter configuration. Traditionally, a multicast tree does not contain any circles, and the first characteristic is that a multicast tree has better performance if it contains some circles. Note that a multicast tree has several branches. If a path is added between the leave nodes on different branches, the segment between them on the multicast tree is protected. Based the two characteristics, the survivable multicast sessions routing problem is formulated into an Integer Linear Programming (ILP). Then, a heuristic algorithm, named the adaptive shared segment protection (ASSP) algorithm, is proposed for multicast sessions. The ASSP algorithm need not previously identify the segments for a multicast tree. The segments are determined during the algorithm process. Comparisons are made between the ASSP and two other reported schemes, link disjoint trees (LDT) and shared disjoint paths (SDP), in terms of blocking probability and resource cost on CERNET and USNET topologies. Simulations show that the ASSP algorithm has better performance than other existing schemes.

• KSII Transactions on Internet and Information Systems (TIIS)
• /
• 제15권9호
• /
• pp.3138-3150
• /
• 2021

Multimedia services on the Internet are continuously increasing. Accordingly, the demand for a technology for efficiently delivering multimedia traffic is also constantly increasing. The multicast technique, that delivers the same content to several destinations, is constantly being developed. This technique delivers a content from a source to all destinations through the multicast tree. The multicast tree with low cost increases the utilization of network resources. However, the finding of the optimal multicast tree that has the minimum link costs is very difficult and its calculation complexity is the same as the complexity of the Steiner tree calculation which is NP-complete. Therefore, we need an effective way to obtain a multicast tree with low cost and less calculation time on SDN-based smart network platforms. In this paper, we propose a new multicast tree generation algorithm which produces a multicast tree using an agent trained by model-based meta reinforcement learning. Experiments verified that the proposed algorithm generated multicast trees in less time compared with existing approximation algorithms. It produced multicast trees with low cost in a dynamic network environment compared with the previous DQN-based algorithm.

• 한국컴퓨터정보학회논문지
• /
• 제9권3호
• /
• pp.189-194
• /
• 2004

본 논문에서는 클러스터 기반의 멀티캐스트 라우팅 문제 해법을 위한 Simulated Annealing(SA) 알고리즘을 제안한다. 멀티캐스트는 한 점에서 다수의 집단 구성원들에게 데이터를 전송하는 것으로 이는 멀티캐스트 트리를 구성하여 해결할 수 있다. 즉, 전체 네트워크를 몇 개의 클러스터로 분할한 후 클러스터 내부를 멀티캐스트 트리로 구성하여 해결할 수 있다. 멀티캐스트 트리는 최소비용 스타이너 트리로 구성할 수 있다. 본 논문에서는 SA알고리즘을 최소비용 스타이너 트리에 적용하였다. 특히, SA 알고리즘에서는 냉각 스케줄을 어떻게 설정하느냐에 따라 알고리즘의 성능에 영향을 준다. 따라서 본 논문에서는 멀티캐스트 라우팅 문제를 위한 SA 알고리즘의 냉각 스케줄을 제안하고, 그 결과를 분석한다.

• Current Optics and Photonics
• /
• 제1권4호
• /
• pp.315-324
• /
• 2017

In recent years, multicast services such as high-definition television (HDTV), video conferencing, interactive distance learning, and distributed games have increased exponentially, and wavelength-division multiplexing (WDM) networks are considered to be a promising technology due to their support for multicast applications. Multicast survivability in WDM networks has been the focus of extensive attention since a single-link failure in an optical network may result in a massive loss of data. But the improvement of network survivability increases energy consumption due to more resource allocation for protection. In this paper, an energy-efficient multicast algorithm (EEMA) is proposed to reduce energy consumption in WDM networks. Two cost functions are defined based on the link state to determine both working and protection paths for a multicast request in WDM networks. To increase the number of sleeping links, the link cost function of the working path aims to integrate new working path into the links with more working paths. Sleeping links indicate the links in sleep mode, which do not have any working path. To increase bandwidth utilization by sharing spare capacity, the cost function of the protection path is defined to use sleeping fibers for establishing new protection paths. Finally, the performance of the proposed algorithm is evaluated in terms of energy consumption, and also the blocking probability is evaluated under various traffic environments through OPNET. Simulation results show that our algorithm reduces energy consumption while maintaining the quality of service.