• Journal of the Korea Computer Industry Society
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• v.6 no.3
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• pp.379-390
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• 2005

Intensive studies have been made in the area of VOD server Multimedia files in the VOD sever are characterized with the large volume of data, the requirements of synchronization and real-time playback of streams. The basic goal of the study is to find an efficient mechanism to allow maximum number of users under the limited resources such as Buffer size and disk bandwidth. we propose a efficient $pre\_fetching$ policy for multimedia services with dynamic monitoring and management of VOD sever resources. Simulation results show that the rate of buffer usage and service time of proposed scheme are about $28\%$ performance improved than that of traditional methods. This implies that our method can allow much more users for given resources.

• Journal of Broadcast Engineering
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• v.24 no.2
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• pp.329-340
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• 2019

Recently, broadcasting technologies have evolved as high-quality AV services such as domestic terrestrial UHD(Ultra-High Definition) broadcasting have been increasing, and broadcasting standards have been newly defined. Also, as network technology develops, contents are consumed not only in the country but also the world. Accordingly, content insertion technology, which is a method of providing suitable contents in accordance with the national and local environments, will be needed. This paper proposes a content insertion service system model and synchronization scheme using ATSC(Advanced Television Systems Committee) 3.0 Event Signaling standard under heterogeneous network environment of broadcasting network and internet network based on transmission standard DASH(Dynamic Adaptive Streaming over HTTP)/ROUTE(Real time Object delivery Over Unidirectional Transport) and MMT(MPEG Media Transport) of terrestrial UHD broadcasting. It also verifies that the service operates in an environment that meets the broadcast standard.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.9 no.5
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• pp.943-950
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• 2005

Recently, many of researches on stream transmission for satisfying each of different real-time transmission condition of the multimedia data that demands various service quality through high-speed networks have been studied actively. In this paper, we design a scheme that discriminately reserves the network resources for the transmission of each multimedia application and propose a bandwidth allocation scheme for improving the utilization ratio of free resources. And we also propose a pipelining scheme for providing flexible real-time transmission. The proposed schemes can be used to support a real-time transmission by applying feedback transmission control method based on receiving buffer for guaranteeing the synchronization conditions requested by the multimedia data. Moreover, we propose a transmission control scheme that can take the amount of network resources down to the minimum amount within the range of permissible error-range under the guarantee with no quality degradation simultaneously when the bottleneck is caused by the network congestion. Finally, we propose a dynamic bandwidth smoothing scheme that can smooth the maximum bandwidth to the demand of each video steam for giving continuous transmission to the delay sensitive video steam between senders and receivers.

• Journal of the Korea Society of Computer and Information
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• v.8 no.3
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• pp.53-60
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• 2003

In these day, Digital Contents is authorized in forms of HTML and various kind of multi-media by an enterprise and/or organization. At this circumstances, it is very hard or impossible to search a contents between them. Futhermore, you may have to change your contents service systems to extend to cover more user services needs. On this paper, we propose a new architecture to get extendability and empowered interoperability without any maintenance, update or changes. And we introduce the OMG's CORBA to make fault resilient system and to provide a load balancing using a distributed process mechanism. Even more, we adopted the SyncML specification. It can help us to make it real to synchronize between DBMS at real-time. So all these are support easy content synchronization and user-friendness.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.17 no.1
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• pp.68-75
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• 2013

Recently IPTV that transmits multimedia contents in real time through internet, cable TV net and satelite net gets the limelight. But IPTV service that gives service to users by various media has a problem of not supporting user certification fully. This paper suggests a certification model which prevents getting access permission of IPTV service by sending illegal certification information by adolescent through integrating mobile communication technique with RFID(Radio Frequency IDentification) technique which is a key technique of Ubiquitous environment. This model performs the process of adult certification by keeping synchronization with user's certificaiton information that is saved in data-base of certification server and contents server after getting the system of class categorization in contents server to overcome disadvantage of simple adult certification system that is popular in the existing internet. Also, it adapts double hash chain technique not to down load illegally contents without the permission of manager even if an adolescent gets manager's approval key.

• Journal of the Korea Computer Industry Society
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• v.7 no.3
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• pp.217-226
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• 2006

Intensive studies have been made in the area of N-VOD server Multimedia files in the N-VOD sever are characterized with the large volume of data, the requirements of synchronization and real-time playback of streams. The basic goal of the study is to find an efficient mechanism to allow maximum number of users under the limited resources such as Buffer size and disk bandwidth. we propose a efficient VCR-LIKE operations and buffer, disk scheduling policy for multimedia services with management of VOD sever resources. Simulation results show that the rate of buffer usage and service time of proposed scheme are about 18% performance improved than that of traditional methods. This implies that our method can allow much more users for given resources.

• Journal of KIISE:Computing Practices and Letters
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• v.9 no.1
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• pp.13-24
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• 2003

MPEG-4 is a standard for multimedia applications and provides a set of technologies to satisfy the needs of authors, service providers and end users alike. In this paper, we suggest a Real-time Multiple Circular Buffer (M4RM Buffer) model, which is suitable for streaming these MPEG-4 contents efficiently. M4RM buffer generates each structure of the buffer, which matches well with each object composing an MPEG-4 content, according to the transferred information, and manipulates multiple read/write operations only by its reference. It divides the decoder buffer and the composition buffer, which are described in the standard, by the unit of frame allocated to minimize the range of access. This buffer unit of a frame is allocated according to the object description. Also, it processes the objects synchronization within the buffer and provides APIs for an efficient buffer management to process the real-time user events. Based on the performance evaluation, we show that M4RM buffer model decreases the waiting time in a buffer frame, and so allows the real-time streaming of an MPEG-4 content using the smaller size of the memory block than IM1-2D and Window Media Player.

• Journal of Internet Computing and Services
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• v.16 no.2
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• pp.1-6
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• 2015

In this paper, we designed an embedded audio video bridging (AVB) platform based on IEEE 802.1BA for real-time multimedia transmission in smart-car, smart-home, smart-theater, and then evaluated a performance of the implemented platform by analysis of IEEE 802.1AS (time synchronization protocol) and IEEE 802.1Qat (stream reservation protocol). Especially, the AVB Layer-2 protocol of MRP(Multiple Registration Protocol), MMAP(Multicast Address Acquisition Protocol), IEEE 1722, 1722.1 etc. was and implemented by linux based operating system. It is shown by interoperability tests with commercial products that the implemented platform transmits real-time multichannel AV data over AVB networks for Multichannel Multimedia Transmission.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.8 no.5
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• pp.1726-1743
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• 2014

DDoS (Distributed Denial of Service) has been a continuous threat to the cyber world with the growth in cyber technology. This technical evolution has given rise to a number of ultra-sophisticated ways for the attackers to perform their DDoS attack. In general, the attackers who generate the denial of service, use the vulnerabilities of the TCP. Some of the vulnerabilities like SYN (synchronization) flooding, and IP spoofing are used by the attacker to create these Distributed Reflected Denial of Service (DrDoS) attacks. An attacker, with the assistance of IP spoofing creates a number of attack packets, which reflects the flooded packets to an attacker's intended victim system, known as the primary target. The proposed scheme, Efficient Spoofed Flooding Defense (ESFD) provides two level checks which, consist of probing and non-repudiation, before allocating a service to the clients. The probing is used to determine the availability of the requested client. Non-repudiation is taken care of by the timestamp enabled in the packet, which is our major contribution. The real time experimental results showed the efficiency of our proposed ESFD scheme, by increasing the performance of the CPU up to 40%, the memory up to 52% and the network bandwidth up to 67%. This proves the fact that the proposed ESFD scheme is fast and efficient, negating the impact on the network, victim and primary target.

• Journal of KIISE
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• v.44 no.8
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• pp.767-773
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• 2017

In a distributed system environment, such as a cloud database, the tail latency needs to be kept short to ensure uniform quality of service. In this paper, through experiments on a Cassandra database, we show that long tail latency is caused by a lack of memory space because the database cannot receive any request until free space is reclaimed by writing the buffered data to the storage device. We observed that, since the performance of the storage device determines the amount of time required for writing the buffered data, the performance degradation of Solid State Drive (SSD) due to garbage collection results in a longer tail latency. We propose a garbage collection synchronization technique, called SyncGC, that simultaneously performs garbage collection in the java virtual machine and in the garbage collection in SSD concurrently, thus hiding garbage collection overheads in the SSD. Our evaluations on real SSDs show that SyncGC reduces the tail latency of $99.9^{th}$ and, $99.9^{th}-percentile$ by 31% and 36%, respectively.