다양한 기술들이 하나로 융합된 VoIP(Voice over Internet Protocol) 서비스는 IP 망을 통해 음성뿐만 아니라 멀티미디어 서비스와 각종 부가서비스를 제공한다. 현재 대역폭 사용효율과 저비용성 등의 장점들 때문에 기존 PSTN 전화에서 VoIP 시스템으로 비즈니스가 전환되고 있다. 이러한 것이 가능한 이유는 기존의 회선교환 네트워크를 대신하여 디지털화된 정보가 IP 패킷 형태로 여러 계층의 컴퓨터로 구성된 패킷교환망을 통해 전달되기 때문이다. 반면에 이러한 형태의 시스템들이 기존 IP네트워크 환경에서의 취약점과 융합되어 발생되는 신규 취약점 등에 의해서 각종 Fraud가 발생하고 있다. 2012년 상반기 Fraud call의 46%가 VoIP 전화기에서 만들어지고 있다는 조사 결과도 있듯이 Fraud Call의 피해는 상당하다. 따라서 Fraud에 대한 손실예방을 위해 대책마련이 필요하다. 특히, Fraud Call의 피해는 주로 국제 통화를 이용할 때 과금 피해로 나타나고 있어, 이와 관련된 SIM Box에 의한 Toll Bypass Fraud에 대한 분석과 이를 검출할 수 있는 방안마련이 요구된다. 일반적으로는 DPI(Deep Packet Inspection)를 기반으로 주요 Signature 또는 통계정보를 이용한 다양한 검출 방안이 제안되었으나, Fraudster 역시 이를 회피하기 위해 다양한 방법을 사용하고 있다. 특히, VoIP에서 Call Setup과 Termination과정을 수행하는 SIP Signal을 암호화 하거나 여러 경로로 전송하는 방식을 사용함으로써 감지를 회피하고 있다. 본 논문은 Fraud call의 감지 회피를 효과적으로 방지할 수 있도록 VoIP 트래픽의 특성과 VoIP Fraud 중 SIM Box Fraud의 행위분석을 결합한 방법론을 제안한다. 또한 제안된 방법론을 적용하여 Toll Bypass Fraud와 관련된 VoIP 서비스 제공자의 장비를 검출하는 방법을 제시한다. Voice over IP (VoIP) is a technology for the delivery of voice communications and multimedia sessions over Internet Protocol (IP) networks. Instead of being transmitted over a circuit-switched network, however, the digital information is packetized, and transmission occurs in the form of IP packets over a packet-switched network which consist of several layers of computers. VoIP Service that used the various techniques has many advantages such as a voice Service, multimedia and additional service with cheap cost and so on. But the various frauds arises using VoIP because VoIP has the existing vulnerabilities at the Internet and based on complex technologies, which in turn, involve different components, protocols, and interfaces. According to research results, during in 2012, 46 % of fraud calls being made in VoIP. The revenue loss is considerable by fraud call. Among we will analyze for Toll Bypass Fraud by the SIM Box that occurs mainly on the international call, and propose the measures that can detect. Typically, proposed solutions to detect Toll Bypass fraud used DPI(Deep Packet Inspection) based on a variety of detection methods that using the Signature or statistical information, but Fraudster has used a number of countermeasures to avoid it as well. Particularly a Fraudster used countermeasure that encrypt VoIP Call Setup/Termination of SIP Signal or voice and both. This paper proposes the solution that is identifying equipment of Toll Bypass fraud using those countermeasures. Through feature of Voice traffic analysis, to detect involved equipment, and those behavior analysis to identifying SIM Box or Service Sever of VoIP Service Providers.

Time and frequency alignment is critical for ensuring QoS for application such as voice, real-time video, wireless hand-off, and data over a converged access medium. To satisfy the accuracy of time synchronization, both adjusting Communication path asymmetry and ratio of frequency between the time-aware systems are important. Network Time Protocol (NTP) is not satisfies time-sensitive applications. IEEE 1588 Precision Time Protocol (PTP) and IEEE 802.1AS don' t calculate the communication path asymmetry. We propose the Single-TimeSync frame for reducing the number of control frames, adjusting propagation delay asymmetry and ratio of frequency originated with slave time-aware station clock. We simulate with base model in OPNET.

Time and frequency alignment is critical for ensuring QoS for applications such as voice, real-time video, wireless hand-off, and data over a converged access medium. To satisfy the accuracy of time synchronization, propagation delay measurement is required between time-sensitive devices. There is existing network technology for time synchronization, such as network time protocol (NTP), IEEE 1588 precision time protocol (PTP), and IEEE 802.1AS. NTP, however, is not suitable for synchronization in time-sensitive applications. IEEE 1588 PTP and IEEE 802.1AS have problems where there are too many messages in LAN. We propose a single frame format and a method of propagation delay measurement using a single frame in bridged LANs. The experiment results show that the proposed method reduces time variation from NTP and control messages about 47% from IEEE 802.1AS.

Today, A matter of concern of home network technology increase. The standard of communication between home network devices are required. IEEE 802.1 AVB(Audio/Video Bridging) specifies transmission method for time-sensitive data between these devices using Ethernet in bridged local area networks. IEEE 802.1 AVB and IEEE 1588 PTP(Precision Time Protocol) have various message type for grandmaster selection and synchronize the devices. These messages bring on complexity protocol. We propose a method that uses Single TimeSync frame in order to the problem. Our proposal is appropriate process complexity and low transmission delay for home network by using the TimeSync frame. Furthermore, after all devices are adjusted to the single TimeSync frame, a resource reservation, a forwarding and queueing rule are needed for a time-sensitive application.

With the growth of digital media devices, researchers are developing techniques for transmission of real-time trafficover the network. Above all, network techniques that utilize Ethernet are in the limelight because of the advantages of Ethernet. A standardized network technique for isochronous traffic over Ethernet is in progress in IEEE 802.1 Audio/Video Bridge Task Group (AVB TG). This paper proposes a network technique for real-time traffic over an Ethernet model, that is, a AVB model with a synchronization method between devices. This paper proposes time synchronization and resource reservation for transmission of real-time traffic in synchronized devices. In this paper, we implement a AVB model through OPNET, and analyze the efficiency of the proposed methods.

By growth of digital media devices, a number of researches are in progress for transmission of isochronous traffic over network. Above all, network techniques that apply Ethernet, are in the limelight because of advantages of Ethernet. A standardization of network technique for isochronous traffic over Ethernet is in progress in IEEE 802.1 AVB TG. This paper proposed network technique for isochronous traffic over Ethernet model, that is, synchronous Ethernet model with synchronization method between devices. And this paper proposed bandwidth reservation method for transmission of isochronous traffic in synchronized devices. In this paper, synchronous Ethernet model is implemented through OPNET, efficiency of proposed methods is analyzed.

An Ethernet PON (Passive Optical Network) is an economical and efficient access network that has received significant research attention in recent years. A MAC (Media Access Control) protocol of the PON, the next generation access network, is based primarily on TDMA (Time Division Multiple Access). In this paper, we addressed the problem of a dynamic bandwidth allocation in QoS (Quality-of-Service) based Ethernet PONs. We augmented the bandwidth allocation algorithms to support QoS in a differentiated service framework. Our differentiated bandwidth guarantee allocation (DBGA) algorithm allocates effectively and fairly the bandwidths between end-users. Moreover, we showed that a DBGA algorithm that perform weighted bandwidth allocation for high priority packets results in a better performance in terms of average and maximum packet delay, as well as the network throughput compared with some other dynamic allocation algorithms. We used the simulation to study the performance and validate the effectiveness of the proposed algorithm.

Ethernet passive optical network is an economical and efficient access network that has received significant research attention in recent years. A MAC(Media Access Control) protocol of PON, the next generation access network, is based on TDMA(Time Division Multiple Access) basically. In this thesis, we addressed the problem of dynamic bandwidth allocation in QoS based Ethernet PONs. We augmented the bandwidth allocation to support QoS in a differentiated services framework. Our differentiated bandwidth guarantee allocation(DBGA) allocates effectively and fairly bandwidths among end users. Moreover, we showed that DBGA that perform weighted bandwidth allocation for high priority packets result in better performance in terms of average and maximum packet delay, as well as network throughput compared with existing dynamic bandwidth allocations. We used simulation experiments to study the performance and validate the effectiveness of the proposed bandwidth allocations.

An Ethernet PON (Passive Optical Network) is an economical and efficient access network that has received significant research attention in recent years. A MAC (Media Access Control) protocol of the PON, the next generation access network, is based primarily on TDMA (Time Division Multiple Access). In this paper, we addressed the problem of a dynamic bandwidth allocation in QoS (Quality-of-Service) based Ethernet PONs. We augmented the bandwidth allocation algorithms to support QoS in a differentiated service framework. Our differentiated bandwidth guarantee allocation (DBGA) algorithm allocates effectively and fairly the bandwidths between end-users. Moreover, we showed that a DBGA algorithm that perform weighted bandwidth allocation for high priority packets results in a better performance in terms of average and maximum packet delay, as well as the network throughput compared with some other dynamic allocation algorithms. We used the simulation to study the performance and validate the effectiveness of the proposed algorithm.

An N/spl times/N star coupler and N optical network units with a circulator and two fiber Bragg gratings were employed to form a fully transparent, 155 Mb/s optical star network over the existing asynchronous transfer mode (ATM) passive optical network (PON) system.

We propose a method to implement a 155-Mb/s optical star network using existing passive optical network (PON) cable plant and demonstrate its feasibility experimentally. The light-emitting diode- (LED) based optical star network, wavelength-compatible with the asynchronous transfer mode (ATM) PON system, showed a power penalty of 1.1 dB compared to back-to-back connection. The overlay network had little effect on ATM PON signals.

We propose a lightpath routing reconfiguration algorithm minimizing the number of OXCs. We present the exact problem description in integer linear programming formulation and show several examples. From experimental results, we found that a considerable number of OXCs can be saved.