• Proceedings of the Korea Information Processing Society Conference
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• 2007.05a
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• pp.125-128
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• 2007

최근 사용자의 멀티미디어 서비스 요구가 보편화되면서 네트워크에 걸리는 부하가 늘어나게 되었고, 사용자들이 미디어를 다운로드한 후 플레이하는 방법보다 스트리밍 서비스를 선호함에 따라 실시간성이 더욱 중요시되고 있다. 웹 서비스에 전통적으로 사용되는 프록시 서버는 네트워크의 가장자리에 위치하여 클라이언트와 서버 사이의 거리 때문에 발생하는 문제를 주로 해결한다. 하지만 고 대역폭과 긴 서비스 시간이라는 특징을 가지는 멀티미디어 스트리밍 서비스에서는 전통적인 웹 프록시의 장점을 제대로 활용하기 어렵다. 본 논문에서는 미디어 스트리밍 서비스에서 네트워크 트래픽을 감소시키고 서비스 지연시간을 줄이기 위한 새로운 캐슁 전략을 제안한다. 제안된 전략에서 프록시 서버는 미디어 데이터의 일부와 미디어의 프리픽스를 캐슁하여 클라이언트가 요청한 미디어를 바로 인접한 프록시에서 찾도록 하여, 고 대역폭을 사용하는 스트리밍 시스템에서 네트워크 부하와 초기 지연을 줄인다.

• Proceedings of the Korean Information Science Society Conference
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• 2005.11a
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• pp.319-321
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• 2005

이동 애드 혹 네트워크은 빈번한 위상 변화가 일어난다. 이에 대처하기 위해 비상태 멀티캐스팅이나 위상 변화에 강한 특성을 지니는 오버레이 멀티캐스트 프로토콜들이 제안되고 있다. 하지만 이들의 대부분은 소규모 그룹에 대한 멀티캐스트만을 지원한다. 그러나 이동 애드 혹 네트워크의 대표적인 응용들은 대규모 그룹 통신을 사용하므로 확장성 문제는 해결되어야 한다. 따라서 본 논문에서는 이를 개선하기 위해 단일 홉 클러스터링과 프록시 노드 사용을 제안한다. 단일 홉 클러스터링은 구조적인 관리가 필요한 노드 수를 줄일 수 있으며 프록시 노드는 단일 홉 클러스터링으로 줄어든 노드들에게 계층화된 포워딩을 제공한다.

• Proceedings of the Korean Information Science Society Conference
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• 2004.04a
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• pp.874-876
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• 2004

본 논문에서는 트랜스코딩가 미디어캐슁 기법을 적목한 프록시 시스템인 DCMS(Dual Caching proxy for adaptive Multimedia Streaming service)를 제안한다. 미디어 데이터 특성을 이용해서 DCMS는 전체 파일 중 파일의 시작 부분만을 미리 캐쉬에 저장하여 클라이언트가 미디어 서비스를 요청하면, 서버를 대신해 데이터를 클라이언트로 전송해주면서 데이터 블록의 뒷부분부터 미리 선반입(Pre-fetching)함으로써 미디어 재생에 끊김이 없도록 한다. 그리고 미디어 데이터를 네트워크 대역폭, 무선단말기 수용성과 사용자 선호도를 고려한 트랜스코딩을 통해 미디어 데이터의 질을 레벨화 하여 저장함으로써 각 클라이언트에 적합한 미디어 데이터를 바로 제공한다.

• KIPS Transactions on Computer and Communication Systems
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• v.2 no.6
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• pp.265-278
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• 2013

With the recent advancements in various wireless communication technologies, the importance of mobile multicasting is coming to the fore, in an effort to use network resources more efficiently. In the past, when various mobile IP-based multicast techniques were proposed, the focus was put on the costs needed for network delivery for providing multicast services, as well as on minimizing the multicast handover delay. For techniques using MIPv6 (Mobile IPv6), a host-based mobility management protocol, however, it is fundamentally difficult to resolve the problems of handover delay and tunnel convergence. To resolve these problems, a network-based mobility management protocol called PMIPv6 (Proxy Mobile IPv6) was standardized. Although performance is improved in PMIPv6 over MIPv6, it still suffers from the problems of handover delay and tunnel convergence. In this paper, to overcome these limitations, a technique called LFH (Low-cost and Fast Handoff) is proposed for fast and low-cost mobility management with multicasting support in PMIPv6 networks. To reduce the interactions between the complex multicast routing protocol and the multicast messages, a simplified proxy method called MLD (Multicast Listener Discovery) is implemented and modified. Furthermore, a TCR (Tunnel Combination and Reconstruction) algorithm was used in the multicast handover procedure within the LMA (Local Mobility Anchor) domain, as well as in the multicast handover procedure between domains, in order to overcome the problem of tunnel convergence. As a result, it was found that LFH has reduced multicast delay compared to other types of multicast techniques, and that it requires lower costs as well.

• Journal of the Korea Society of Computer and Information
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• v.15 no.6
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• pp.57-64
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• 2010

Due to the limited storage space in video proxy server, it is often required to replace the old video data which is not serviced for long time with the newly requested video. This replacement causes the service delay and increase of network traffic. To circumvent this problem, we propose the an efficient replacement scheme in a video proxy server. In addition, we present a video data management technique for decreasing the number of replacement in video proxy server. For this purpose, we employ a memory in video proxy server. If the video segment which is loaded in memory is requested once again by a different user, this segment is resided in memory. The video in the memory is stored in the video proxy server depending on the consuming pattern by users. The simulation results show that the proposed algorithm performs better than other algorithms in terms of packet hit rate and number of packet replacement.

• Journal of Korea Multimedia Society
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• v.8 no.7
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• pp.943-952
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• 2005

This paper proposes a user's mobility based cooperative proxy caching policy for effective resource management of continuous media objects in mobile environments. This policy is different from the existing proxy caching policies in terms of how to exploit users' mobility. In other words, existing caching policies work based on the information about objects by referring to users' requests within a specified domain whereas the proposed caching policy runs by utilizing a number of users' requests across several domains. So, the proposed policy is applicable to random requests in mobile environments. Moreover, we also propose a replacement policy based on weights and playback time. To check the efficiency of the proposed caching policy, the proposed replacement policy is run with different size of caching unit: object or segment. The result of performance evaluation tells that segment sizes, ratio of users' mobility and weights are major factors for the efficient operation of the cooperative caching.

• Journal of the Korea Society of Computer and Information
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• v.15 no.11
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• pp.135-142
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• 2010

QoS in the proxy system are under heavy influence from interferences such as congestion, latency, and retransmission. Also, multi-level streaming services affects from temporal synchronization, which lead to degrade the service quality. This paper proposes a new segment-based buffer management mechanism which reduces performance degradation of streaming services and enhances throughput of streaming due to drawbacks of the proxy system. The proposed paper optimizes streaming services by: 1) Use of segment-based buffer management mechanism, 2) Minimization of overhead due to congestion and interference, and 3) Minimization of retransmission due to disconnection and delay. This paper utilizes fuzzy value $\mu$ and cost weight $\omega$ to process the result. The simulation result shows that the proposed mechanism has better performance in buffer cache control rate, average packet loss rate, and delay saving rate with stream relevance metric than the other existing methods of fixed segmentation method, pyramid segmentation method, and skyscraper segmentation method.

• The KIPS Transactions:PartA
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• v.15A no.1
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• pp.53-60
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• 2008

Streaming media has contributed to a significant amount of today's Internet Traffic. Like traditional web objects, rich media objects can benefit from proxy caching, but caching streaming media is more of challenging than caching simple web objects, because the streaming media have features such as huge size and high bandwidth. And to support various bandwidth requirements for the heterogeneous ubiquitous devices, a transcoding proxy is usually necessary to provide not only adapting multimedia streams to the client by transcoding, but also caching them for later use. The traditional proxy considers only a single version of the objects, whether they are to be cached or not. However the transcoding proxy has to evaluate the aggregate effect from caching multiple versions of the same object to determine an optimal set of cache objects. And recent researches about multimedia caching frequently store initial parts of videos on the proxy to reduce playback latency and archive better performance. Also lots of researches manage the contents with segments for efficient storage management. In this paper, we define the 9-events of transcoding proxy using 4-atomic events. According to these events, the transcoding proxy can define the next actions. Then, we also propose the segment-based caching policy for the transcoding proxy system. The performance results show that the proposing policy have a low delayed start time, high byte-hit ratio and less transcoding data.

• Proceedings of the Korean Information Science Society Conference
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• 2002.04a
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• pp.286-288
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• 2002

SIP는 인터넷 텔레포니 신호(Internet Telephony Call)와 같은 멀티미디어 세션을 성립, 변경, 종료시킬 수 있는 응용계층의 호 제어 프로토콜이다. 또한, SIP 프록시 서버(Proxy Server)라는 네트일 호스트로 구축된 인프라를 통해 멀티미디어 통신을 원하는 네트윅상의 사용자를 찾아 멀티미디어 세션(Session)이 성립될 수 있도록 도와준다. SIP는 Request-Response 방식의 프로토콜이기 때문에 요청(Request)과 응답(Response)을 주고받는 일련의 트랜잭션(Transaction)으로 하나의 Task를 완성한다. 본 논문에서는 rfc2543을 기반으로 기본적인 SIP 트랜잭션을 위한 SIP 스택(Stack)의 설계 및 그 구현 방안을 제지한다.

• Journal of Internet Computing and Services
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• v.9 no.6
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• pp.37-48
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• 2008

VoIP service is a transmission of voice data using SIP protocol on IP based network, The SIP protocol has many advantages such as providing IP based voice communication and multimedia service with cheap communication cost and so on. Therefore the SIP protocol spread out very quickly. But, SIP protocol exposes new forms of vulnerabilities on malicious attacks such as Message Flooding attack and protocol parsing attack. And it also suffers threats from many existing vulnerabilities like on IP based protocol. In this paper, we propose a new Virtual Proxy Server system in front of the existed Proxy Server for anomaly detection of SIP attack and stateful management of SIP session with enhanced security. Based on stateful virtual proxy server, out solution shows promising SIP Message Flooding attack verification and detection performance with minimized latency on SIP packet transmission.