• The Transactions of the Korea Information Processing Society
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• v.6 no.9
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• pp.2332-2342
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• 1999

Multicast is an important system-level one-to-many collective communication service. A key issue in designing software multicast algorithms is to consider the trade-off between performance and portability. Based on the LogP model, the proposed parameterized communication model can more accurately characterize the communication network of parallel platforms, Under the parameterized model, we propose an efficient architecture-independent method. OPT-tree algorithm, to construct optimal multicast trees and also investigate architecture-dependent tuning on performance of the multicast algorithm to achieve the truly optimal performance when implemented in real networks. Specifically, OPT-mesh which is the optimized version of the parameterized multicast algorithm for wormhole-switched mesh networks is developed and compared with two other well-known network-dependent algorithms.

• Journal of KIISE:Information Networking
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• v.30 no.5
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• pp.656-667
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• 2003

Congestion control is a key task in reliable multicast along with error control. However, existing tree-based congestion control schemes such as MTCP and TRAMCC are designed for one-to-many reliable multicast and have some drawbacks when they are used for many-to-many reliable multicast. We propose an efficient congestion control mechanism, TMRCC, for tree-based many-to-many reliable multicast protocols. The proposed scheme is based on the congestion windowing mechanism and a rate controller is used in addition. The feedback for error recovery is exploited for congestion control as well to minimize the overhead at the receivers. The ACK timer and the NACK timers are set dynamically reflecting the network condition changes. The rate regulation algorithm in the proposed scheme is designed to help the flows sharing the same link to achieve the fair share quickly The performance of the proposed scheme is evaluated using ns-2. The simulation results show that the proposed scheme outperforms TRAMCC in terms of intra- session fairness and shows good level of responsiveness, TCP-friendliness, and scalability. In addition, we implemented the proposed scheme by integrating with GAM that is one of many-to-many reliable multicast protocols and evaluated the performance in a laboratory-wide testbed.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.31 no.2B
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• pp.137-145
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• 2006

In this paper, we propose a multicast P2Patching technique in the application layer. The P2Patching technique serves VOD stream effectively with Patching in P2P environment. The P2Patching provides multicast tree construction technique that reduces the server load and minimizes the start delay with extended multicast technique. And we provide a fast recovery technique by tree failure and dynamic buffering scheme that guarantees the continuous streaming by frequent tree disconnections. Comparing the method with that of $P2Cast^{[12]}$, we obtained the better performance by our scheme in terms of average join count, service rejection probability, tree recovery failure and buffer starvation. The average about 16$\%$ of the improvement is shown by the simulation. Most of all, the performance of buffer starvation and average join count shows a significant improvement than that of P2Cast.

• Proceedings of the Korea Multimedia Society Conference
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• 2003.11a
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• pp.140-143
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• 2003

최근 인터넷의 급속한 발전은 다양한 서비스를 창출하였으며, 모든 사용자에게 제공되던 브로드 캐스팅적 서비스에서 일부 사용자만을 위한 여러 가지 새로운 서비스로 변화하고 있다. 새로운 형태의 서비스의 경우 그룹 형태의 사용자들의 안전성을 보장하면서 효율적인 관리 구조에 대한 연구보다는 그룹의 서비스의 효율성에 목적을 두어 사용자의 프라이버시 침해에 대한 논란을 야기 시키고 있다. 따라서 본 논문에서는 기존의 멀티캐스팅 그룹 설정에 기반한 LBT 트리에 그룹 네트워크가 설정 될 경우 그룹원들간의 안전성을 제공하면서 관리의 효율성과 확장성 갖는 관리 방식을 제안하고자 한다. 제안 방식은 LBT트리의 특징을 그대로 유지하면서 기존 방식에서의 안전성에 대한 취약점을 보완하여 보다 안전하고 효율적인 방식을 제안하였다.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.42 no.9 s.339
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• pp.29-40
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• 2005

In this paper, we propose a Cluster-based Multicast Routing (CMR) suitable for mobile ad-hoc networks. The main features that our proposed method introduces are the following: a) mobility-based clustering and group based hierarchical structure in order to effectively support stability and scalability, b) group based mesh structure and forwarding tree concepts in order to support the robustness of the mesh topologies which provides limited redundancy and the efficiency of tree forwarding simultaneously, and c) combination of proactive and reactive concepts which provide low route acquisition delay and low overhead. The performance evaluation of the proposed protocol is achieved via modeling and simulation. The corresponding results demonstrate the Proposed multicast protocol's efficiency in terms of packet delivery ratio, scalability, control overhead, end-to-end delay, as a function of mobility, multicast group size, and number of senders.

• Proceedings of the Korean Information Science Society Conference
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• 2005.07a
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• pp.553-555
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• 2005

이중 공유기반 트리 방식인 CBT 방식은 송신자와 수신자 모두 센터 노드(Core)에 이르는 최단경로를 통해 데이터를 주고받는 방식이다. 이 방식은 Core를 이용하여 멀티캐스트의 한계인 확장성문제를 해결하기 위해서 사용된 방식이다. 그러나 현재 멀티미디어 라우팅방식은 Best-Effort 방식의 패킷 스위칭은 가능한 한 패킷을 전송하려 하기 때문에 Core와 RP를 중심으로 데이터의 폭주 현상을 유발한다. 우리는 이와 같은 문제를 해결하기 위해서 RED 알고리즘을 이용한 Anycast 방식을 제안한다. Anycast 프로토콜은 Anycast 주소를 가진 수신자 그룹 멤버들 중, 가장 근접한 라우터나 지역의 Anycast 그룹 멤버들에게 패킷을 재분배할 수 있는 최적의 서버 또는 호스트에게 패킷을 전달하는 방식이다. 이와 같이 Anycast는 Core의 패킷을 재분배하여 근접한 라우터로 재분배 하여 최적의 호스트에게 전달할 수 있다. Core의 패킷을 재분배하기 위해서는 RED 알고리즘을 도입하여 Core으 트래픽 증가를 분산시킨다.

• The KIPS Transactions:PartC
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• v.12C no.2 s.98
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• pp.267-280
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• 2005

In this paper, we implement and verify XMIP integrating IETF Mobile IP and the Explicit Multicast mechanism for a great number of small group multicast communications. U a source node sends Xcast packets explicitly inserting destination nodes into the headers, each Xcast router decides routes and forwards the packets toward each destination node based on unicast routing table without the support of multicast trees. n is a straightforward and simple multicast mechanism just based on a unicast routing table without maintaining multicast states because of the inheritance from the Explicit Multicast mechanism. This research modifies and extends the functionality of IETF Mobile IP's mobility agents, such as HA/FA to HA+/FA+ respectively, considering interworking with Xcast networks. Xcast packets captured by HA+ are forwarded into X-in-X tunnel interfaces for each FA+ referred to the binding table of HA.. This X-in-X tunneling mechanism can effectively solve the traffic concentration problem of IETF Mobile IP multicast services. Finally WLAN-based testbed is built and a multi-user Instant messenger system is developed as a Xcast application for finally verify the feasibility of the implemented XMIP/Xcast protocols.

• Journal of KIISE:Information Networking
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• v.30 no.3
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• pp.407-415
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• 2003

As services requesting data transfer from a sender to a multiple number of receivers become popular, efficient group communication mechanisms like multicast get much attention. Since multicast is more efficient than unicast in terms of bandwidth usage and group management for group communication, many multicast protocols providing scalability and reliability have been proposed. Recently, router-supported reliable multicast protocols have been proposed because routers have the knowledge of the physical multicast tree structure and, in this scheme, repliers which retransmit lost packets are selected by routers. Repliers are selected dynamically based on the network situation, therefore, any receiver within a multicast group can become a replier Hence, all receivers within a group maintains a buffer for loss recovery within which received packets are stored. It is an overhead for all group receivers to store unnecessary packets. Therefore, in this paper, we propose a new scheme which reduces resource usage by discarding packets unnecessary for loss recovery from the receiver buffer. Our scheme performs the replier selection and the loss recovery of lost packets based on the LSM [1] model, and discards unnecessary packets determined by ACKs from erasers which represent local groups.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.30 no.5B
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• pp.253-263
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• 2005

This paper proposed a mobile multicast technique to satisfy end-to-end QoS for various user requirements in mobile network environment. In order to provide seamless mobility, fast handoff technique was applied. By using L2 mobile trigger, it was possible to minimize remarkable amount of packet loss by delay occurred during handoff. To provide efficient multicast, concept of hierarchy was introduced to Xcast++, which results in a creation of HXcast++. HXcast++ optimized transfer path of multicast and reduced expensive multicast maintenance costs caused by frequent handoff. Suggestion of GMA (Group Management Agent) mechanism allows joining to group immediately without waiting IGMP Membership query during handoff. GMA mechanism will minimize the delay for group registration process and the resource usage due to delay of withdrawal process. And also use of buffering & forwarding technique minimized packet loss during generation of multicast tree. IntServ/RSVP was used to provide End-to-End QoS in local domain and DiffServ was used in global domain. To minimize reestablishment of RSVP session delay, extended HXcast++ control messages ware designed to require PATH message. HXcast++ proposed in this thesis is defined as multicast technique to provide end-to-end QoS and also to satisfy various user requirements in mobile network environment.

• Journal of KIISE:Information Networking
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• v.30 no.3
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• pp.329-342
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• 2003

Most of the existing multicast routing protocols for ad-hoc networks do not take into account the efficiency of the protocol for the cases when there are large number of sources in the multicast group, resulting in either large overhead or poor data delivery ratio when the number of sources is large. In this paper, we propose a multicast routing protocol for ad-hoc networks, which particularly considers the scalability of the protocol in terms of the number of sources in the multicast groups. The proposed protocol designates a set of sources as the core sources. Each core source is a root of each tree that reaches all the destinations of the multicast group. The union of these trees constitutes the data delivery mesh, and each of the non-core sources finds the nearest core source in order to delegate its data delivery. For the efficient operation of the proposed protocol, it is important to have an appropriate number of core sources. Having too many of the core sources incurs excessive control and data packet overhead, whereas having too little of them results in a vulnerable and overloaded data delivery mesh. The data delivery mesh is optimally reconfigured through the periodic control message flooding from the core sources, whereas the connectivity of the mesh is maintained by a persistent local mesh recovery mechanism. The simulation results show that the proposed protocol achieves an efficient multicast communication with high data delivery ratio and low communication overhead compared with the other existing multicast routing protocols when there are multiple sources in the multicast group.