비동기식전송모드(ATM)망에서 흐름제어 셀 다중화기

강구홍 서원대학교 응용과학연구소 2001 응용과학연구 Vol.10 No.1

Since First-Come-First-Served discipline makes it is difficult to satisfy the diverse quality of service(QoS) requirements for each connection, traffic isolation has been proposed for guaranteeing the desired QoS throught explicit bandwidth allocation to each virtual connection(VC) in ATM networks. For this purpose, we propose a rate-controlled cell multiplexer using a simple "periodic token-based regulator" per-VC the proposed multiplexer realizes VC isolation, while still operating work-conservingly. We first discuss its major properties, and then examine its features with respect to the characteristics of the output traffic streams and the traffic isolation of individual VC's. We also propose some variants schemes to accommodate the constant bit rate or best-effort services.

NetFlow 데이터를 이용한 실시간 네트워크 트래픽 어노멀리 검출 기법

강구홍,장종수,김기영,Kang Koo-Hong,Jang Jong-Soo,Kim Ki-Young 한국정보처리학회 2005 정보처리학회논문지 C : 정보통신,정보보안 Vol.11 No.1

최근 알려지지 않은 공격(unknown attack)으로부터 네트워크를 보호하기 위한 네트워크 트래픽 어노멀리(anomaly) 검출에 대한 관심이 고조되고 있다. 본 논문에서는 캠퍼스 네트워크의 보드라우터(border router)의 NetFlow 데이터로 제공되는 초당비트수(bits per second)와 초당플로수(flows per second)의 상관관계를 단순회귀분석을 통하여 새로운 어노멀리 검출 기법을 제시하였다. 새로이 제안된 기법을 검증하기 위해 실지 캠퍼스 네트워크에 적용하였으며 그 결과론 Holt-Winters seasonal(HWS) 알고리즘과 비교하였다. 특히, 제안된 기법은 기존 RRDtool에 통합시켜 실시간 검출이 가능하도록 설계하였다. Recently, it has been sharply increased the interests to detect the network traffic anomalies to help protect the computer network from unknown attacks. In this paper, we propose a new anomaly detection scheme using the simple linear regression analysis for the exported LetFlow data, such as bits per second and flows per second, from a border router at a campus network. In order to verify the proposed scheme, we apply it to a real campus network and compare the results with the Holt-Winters seasonal algorithm. In particular, we integrate it into the RRDtooi for detecting the anomalies in real time.

고속망 적합한 NP 기반 인-라인 모드 IDS에 관한 실험

강구홍 서원대학교 미래창조연구소 2004 과학과 문화 Vol.1 No.1

In this paper we propose an In-Line mode network intrusion detection system (NIDS) using Agere network processors, which supports the packet payload inspection to detect the malicious behaviors of attackers based on the well-known attack signatures from Snort, the traffic metering to gather the diverse network traffic statistics via network monitoring, and the packet filtering to protect some specific traffic via access control list. In particular, the mentioned three functions should be done wire-speed under two giga-bit ethernet ports so that we can prevent the intrusions in real-time. We use an industrial PC platform with an x86 processor running Linux, two Gigabit Ethernet ports, and Agere PayloadPlus (APP) 2.5G NP solution. In this prototype system we adapt a two-level searching scheme for guaranteeing fully the wire-speed intrusion detection operation and getting rid of the weakness of In-line mode NIDS, which separates the packet forwarding and the packet payload inspection. We believe this paper describers the approach and presents a first experimental evaluation of NP effectiveness for NIDS.

대용량 ATM 스위치를 위한 2단 구조 ( A2-Stage Architecture for Very Large Scale ATM Switch )

강구홍,이정희,박권철 대한전자공학회 1992 대한전자공학회 학술대회 Vol.1992 No.7

ATM 노드를 위한 WCSFQ-유사 공간 우선순위 정책의 성능분석

강구홍 한국정보처리학회 2005 정보처리학회논문지 C : 정보통신,정보보안 Vol.12 No.6

In ATM and IP networks, high priority packets should be selectively favored over low priority packets in case of congestion. For this purpose, we introduce a space priority policy for ATM nodes in this paper which is very similar to the weighted core-stateless fair queueing(WCSFQ) in IP nodes. We also analyze the loss probabilities for different classes of cells for MMPP/D/1/K with a threshold level, and discuss the numerical results. The numerical results illustrate that the WCSFQ scheme can be used to support the differentiated services in ATM or IP nodes. ATM과 IP 망에서 혼잡발생시 높은 우선순위를 가진 패킷은 낮은 우선순위를 가진 패킷에 비해 영향을 적게 받도록 설계되어야 한다. 이러한 문제 해결을 위해, 본 논문에서는 기존 IP 망에서 사용되는 가중치 CSFQ(Weighted Core-Stateless Fair Queueing)를 ATM 노드의 공간 우선순위(space priority) 정책에 적용하였다. 성능분석을 위해 임계치(threshold)를 갖는 MMPP/D/1/K 큐잉모델의 트래픽 클래스별 셀 손실률을 유도하고 그 결과를 논하였다. 분석결과를 통해 가중치 CSFQ 기법이 ATM 혹은 IP 노드에서 차별화된 서비스 제공에 매우 유용함을 보였다.

ISDN U-접속 선로부호 시뮬레이션 비교연구 ( A Comparative Study of Line Code for ISDN U-Interface )

강구홍,김대영 대한전자공학회 1989 대한전자공학회 학술대회 Vol.1989 No.1

Performance Anomaly of the IEEE 802.11 DCF in Different Frame Error Rate Conditions

강구홍 한국정보처리학회 2012 Journal of information processing systems Vol.8 No.4

We propose an analytic model to compute the station’s saturated throughput and packet delay performance of the IEEE 802.11 DCF (Distributed Coordination Function) in which frame transmission error rates in the channel are different from each other. Our analytic model shows that a station experiencing worse frame error rates than the others suffers severe performance degradation below its deserved throughput and delay performance. 802.11 DCF adopts an exponential back-off scheme. When some stations suffer from high frame error rates, their back-off stages should be increased so that others get the benefit from the smaller collision probabilities. This impact is then recursively applied to degrade the performance of the victim stations. In particular, we show that the performance is considerably degraded even if the frame error rate of the victim station satisfies the receiver input level sensitivity that has been specified in the IEEE 802.11 standard. We also verify the analytic results by the OPNET simulations.

Java Media Framework API를 이용한 방송시스템 구현

강구홍 서원대학교 응용과학연구소 2003 응용과학연구 Vol.12 No.1

Due to the increasing number of real-time multimedia stream type applications like Internet TV, there has been renewed interest in multicast protocols that can reduce the network load greatly compare to the unicast ones. In this paper, we have designed and implemented an IP multicast broadcasting system for these applications especially for On-Air broadcasting and video on demand services. The IP multicast model allows scalable and efficient multi-party communication. However, deployment of IP multicast requires substantial infrastructure modifications for widespread deployment of IGMP and routing protocols as well as complex modifications to IP router's software. Motivated by these programs, we have proposed a limited IP multicasting approach which only supports a local multicasting relying on the multicasting server. We have implemented a client and a server program by Java Media Framework API. In particular, the server program can be running on a web server so that the multicasing server can be implemented on an embeded system and we manage the multicasting server via Internet at remote site. This web server base approach also allows us to manage the media contents separately from the multicasting server system.

ATM망에서 실용적 연결수락제어 기법

강구홍,박상조 한국정보과학회 2002 정보과학회논문지 : 정보통신 Vol.28 No.4

Connection admission control(CAC), which decides whether or not to accept a new call request, is one of the most important preventive congestion control techniques in asynchronous transfer mode(ATM) networks. To develop a practical CAC scheme, first we propose a "Modified Cell Loss Probability MPv", which is based on "Virtual Cell Loss Probability Pv", taking into account mean burst duration of input traffic source and buffer size in ATM networks. MPv computes more accurate cell loss probability than Pv without increasing computational complexity, since Pv is formulated simply form the maximum and the average cell rate of input traffic. Pv is overestimated as compared to the real cell loss probability when the mean burst duration is relatively small to the buffer capacity.Then, we propose a CAC scheme, based on "Modified Virtual Bandwidth(MVB)" method, which may individualize the cell loss probabilities in heterogeneous traffic environments. For the proposed approach, we define the interference intensity to identify interferences between heterogeneous traffic sources and use it as well as MPv to compute MVB. Our approach is well suitable for ATM networks since it provides high bandwidth utilization and guarantees simple and real time CAC computation for heterogeneous traffic environments. 하나의 새로운 호 접속 여부를 결정하는 연결수락제어(CAC:Connection Admission Control)는 비동기식전송모드(ATM:Asynchronous Transfer Mode) 망에서 예방적 과잉밀집제어 기술 중 하나다. 본 논문에서는 실용적 CAC를 개발하기 위해, "가상 셀 손실률 Pv"을 근거로 입력 트래픽 원의 평균 버스트 구간과 ATM 망의 버퍼크기를 고려한 "변형된 가상 셀 손실률 MPv"를 제안한다. Pv는 입력 트래픽의 최대 및 평균 셀 율만으로 계산되기 때문에 트래픽의 평균 버스트 구간이 버퍼 크기에 비해 작으면 Pv는 실질적인 셀 손실률에 비해 과대 평가된다. 제안된 MPv는 계산의 복잡도를 증가시키지 않으면서 Pv보다 더 정확한 셀 손실률을 구할 수 있다.또한, 이질 호원(heterogeneous) 환경에서 각각의 셀 손실률을 계산하는 "변형된 가상 대역폭(MVB: modified virtual bandwidth)" 방법에 근거한 CAC를 제안한다. 이와 같은 새로운 CAC를 제안하기 위해 이질 호 원간 "간섭 강도(interference intensity)"를 정의하고 MVB를 계산할 때 MPv와 더불어 이를 사용한다. 제안된 기법은 이질 호 원 환경 하에서 대역폭 효율을 극대화하고 실현이 간단하며 실시간 계산이 가능하기 때문에 ATM 망에서 유용하게 사용될 수 있다.

ATM망에서 실용적 연결수락제어 기법

강구홍 서원대학교 응용과학연구소 2002 응용과학연구 Vol.11 No.1

Connection admission control(CAC), which decides whether or not to accept a new call request, is one of the most important preventive congestion control techniques in asynchronous transfer mode(ATM) networks. To develop a practical CAC scheme, first we propose a "Modified Cell Loss Probability MP_v", which is based on "Virtual Cell Loss Probability P_v", taking into account mean burst duration of input traffic source and buffer size in ATM networks. MP_v computes more accurate cell loss probability than P_v without increasing computational complexity, since P_v, is formulated simply form the maximum and the average cell rate of input traffic. P_v is overestimated as compared to the real cell loss probability when the mean burst duration is relatively small to the buffer capacity. Then, we propose a CAC scheme, based on "Modified Virtual Bandwidth(MVB)" method, which may individualize the cell loss probabilities in heterogeneous traffic environments. For the proposed approach, we define the interference intensity to identify interferences between heterogeneous traffic sources and use it as well as MP_v to compute MVB. Our approach is well suitable for ATM networks since it provides high bandwidth utilization and guarantees simple and real time CAC computation for heterogeneous traffic environments.