HFC(Hybrid Fiber Coax)망을 통한 인터넷 접속에서 Split connection에 의한 TCP 성능 향상 방안

정충교,전재익 강원대학교 정보통신연구소 2000 정보통신논문지 Vol.4 No.-

For using services like internet in an HFC(Hybrid Fiber Coax) network, end-to-end Direct connection is normally established between a subscriber's PC and a remote server in the external networks. It may increase round trip delay. However, in an HFC network, there is typically a single, static route between a subscriber's PC and the local server complex, whereas in the Internet packets transmitted over the same connection can be routed over different paths. This paper proposes a method to improve the performance by using gateway model to split the end-to-end connection between a subscriber's PC and a external internet server into two distinct connections by reducing the round trip latency for each connection, the gateway speeds up end-to-end performance. By handling packet losses that occur in the HFC network locally, at low latencies and without the remote server even being aware of the loss, the gateway enables faster recovery from packet loss. Furthermore, since it controls data transmissions over the local connection, the gateway's TCP implementation can be optimized for the loss characteristics of the HFC access network, enabling a significant increase in performance when the access network is lossy. Especially in the simulation, by modification of local server complex in an HFC network, it is confirmed that TCP performance in throughput with different round trip delay and with different packet loss rate, is improved when using Split connection other than existing Direct connection network model.

TCP와 유사한 신뢰성이 있는 멀티캐스트

정충교,김홍락 강원대학교 정보통신연구소 2000 정보통신논문지 Vol.4 No.-

IP multicast is an efficient means of sending the same data to a group, but the packets are sent unreliably. Some applications require full reliability, so transport multicast protocols which support full reliability take a growing interest. In this paper, we propose a TCP-like reliable multicast protocol which guarantees reliable, sequenced, and loosely synchronized delivery of multicast streams. We add TCP-like flow control to LMS(Lightweight Multidcast services) error control without any architecture changes of LMS. LMS has been proposed for local recovery and high scalability, but it doesn't support flow control. In order to add TCP flow control to LMS and to avoid feedback implosion, ACK aggregation is necessary. We showed high performance of the proposed protocol via simulation.

인터넷에서의 품질지원형 서비스 전망

정충교 江原大學校 産業技術硏究所 2004 産業技術硏究 Vol.24 No.B

Quality services such as the integrated service and the differentiated service have been expected to be supported by public Internet as multimedia applications proliferate. Despite a lot of techniques for quality services have been devised, the prospect for the deployment of these techniques is not clear yet. In this research feasibility of real world quality service is investigated based on former experiments and recent trends in Internet applications. User network-based quality services are considered as the most feasible and economic short-term solution, which are also flexible in nature. Milestones and key technologies for some specific public network-based quality services are also described.

TCP over ATM에서 non-ATM 접속구간에 의한 성능저하 문제를 해결하기 위한 역방향 제어

정충교,신우근 강원대학교 정보통신연구소 2000 정보통신논문지 Vol.4 No.-

The availble bit rate (ABR) service has been developed to support data traffic over ATM networks and provide end-to-end congestion control at the ATM layer. However, most data applications use to ATM through legacy networks. ABR still experiences congestion at network edges and cannot provide adequate flow control on an end-to-end basis. In this paper, we propose a backward control for solving performance degradation problem at the non-ATM connection point. This is defferent from the conventional end-to-end control, using backward(from congestion point to source) congestion control. This method improves goodput and reduces buffer requirement at the connection point.

ISDN을 통한 인터넷 접속망의 구조

정충교 강원대학교 정보통신연구소 1997 정보통신논문지 Vol.1 No.-

Integration of ISDN and Internet service will promote networking of home PC's and change the PC networking architecture. In a new PC network architecture, the relationship between various network service elements will also change. In this paper, the direction of change in PC network configuration and protocol architecture is investigated, based on the closedness of existing PC network and open characteristics of Internet. Key requirements for the new network environment among general features of ISDN are also provided.

공격자의 자원소진특성을 이용한 분산서비스불능화 (DDoS) 공격에 대한 방어

정충교 江原大學校 産業技術硏究所 2007 産業技術硏究 Vol.27 No.B

A novel DDoS (Distributed Denial-of-Service) defense technique, Exaustiveness-Based Detection, is proposed in this work. It dispenses with the network congestion and the unfairness between users of the Defense-by-Offense technique by incorporating a kind of simple Detect-and-Block scheme (user identification), still improving the effectiveness of the defense in comparison to the original Defense-by-Offense technique, It uses SYN cookies to identify users in the granularity of ip address and to prevent ip address spoofing by the attacker. There can be, however, some probability of false negative (denying service to good clients), if the attacker wisely adapt to the new technique by saving some portion of its bandwidth resource and later mimicking good clients. Quandtadve analysis the requirement for the good clients to be safe from the false negative is provided and a procedure to design the server capacity is explained.

태국어 수사 어원에 관한 연구

이교충 한국외국어대학교 동남아연구소 1996 東南亞硏究 Vol.- No.5

패킷부분재전송기법의 수율 최저 한계

정충교 江原大學校 産業技術硏究所 2008 産業技術硏究 Vol.28 No.A

Wireless carrier sense multiple access (CSMA) systems are widely used but show extremely different transmission efficiency according to the operation environment. Simulation or prototype deployment is needed to see the transmission efficiency of a wireless CSMA system with the partial packet retransmission scheme. The lower bound for the transmission efficiency of such a system is found mathematically in this work. This shows how much the partial packet retransmission scheme improves the transmission efficiency quantitatively. It also shows that the maximum throughput is obtained at higher offered load compared to the conventional CSMA system without the partial packet transmission. The result of this work can be applied to IEEE 802.11 networks or wireless mesh networks.

차별화 서비스에서 공정한 대역폭 보장 방안

정충교,유용수 강원대학교 정보통신연구소 2000 정보통신논문지 Vol.4 No.-

It has been observed that assured service in the differentiated service network cannot guarantee the contracted profile rate fairly. Achieved throughput depends on the profile rates. TCP's congestion avoidance algrorithm causes this. In this paper we proposed 3-drop precedence scheme which is using token bucket and TSW(Time Sliding Window) marker to solve this problem. we showed proposed scheme improves the performance of assured service and this scheme is effective also when the non-responsive UDP traffic sources exist.

한국산 독말풀에 대한연구(Ⅰ) : HPLC에 의한 Hyoscyamine 과 Scopolamine의 정량

도경삼,신민교,송호준,선중기,손인경,백승화 원광대학교기초자연과학연구소 1992 基礎科學硏究誌 Vol.11 No.3

A new method for quantitative determination of Hyoscyamine and Scopolamine in Datura stramonium L. by High Performance Liquid Chromatography(HPLC) was established. A reversed-phase system with a μ Bondapak C18 column using methanol in 0.2% aqueous phosphoric acid(40:60) with PIC A as a mobile phase was developed. Hyoscyamine and Scopolamine were detected at 254nm and the analysis was successfully carried out within 20min.