• Journal of Digital Contents Society
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• v.19 no.8
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• pp.1545-1554
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• 2018

In order to support the mobility of the wireless devices, at least two APs (Access Points) must be arranged in a single AP area to maintain communication area. In the WLAN (Wireless LAN) environment, seamless handover is one of the most important issues in terms of effective utilization of wireless networks and maximization of services for users. On the other hand, SDN (Software-Defined Networking), which is emerging rapidly in recent years, is revolutionizing network management in terms of flexibility, fine control, and convenience. SDN originally reduces latency time or increases network robustness by real-time flow table control reducing or bypassing paths between switches in LAN-based data centers. In this study, we apply OpenFlow, a SDN platform focused on wired LAN, to a dense WLAN environment using legacy APs to implement and evaluate seamless handover for streaming services of digital contents.

• The Journal of Korean Institute of Next Generation Computing
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• v.13 no.6
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• pp.7-20
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• 2017

The advancement of cloud and big data and the considerable growth of traffic have increased the complexity and problems in the management inefficiency of existing networks. The software-defined networking (SDN) environment has been developed to solve this problem. SDN enables us to control network equipment through programming by separating the transmission and control functions of the equipment. Accordingly, several studies have been conducted to improve the performance of SDN controllers, such as the method of connecting existing legacy equipment with SDN, the packet management method for efficient data communication, and the method of distributing controller load in a centralized architecture. However, there is insufficient research on the control of SDN in terms of the quality of network-using applications. To support the establishment and change of the routing paths that meet the required network service quality, we require a mechanism to identify network requirements based on a contract for application network service quality and to collect information about the current network status and identify the violations of network service quality. This study proposes a method of identifying the quality violations of network paths through ontology to ensure the network service quality of applications and provide efficient services in an SDN environment.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.28 no.2
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• pp.485-500
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• 2018

As the size of the system and network environment grows and the network structure and the system configuration change frequently, network administrators have difficulty managing the status manually and identifying real-time changes. In this paper, we suggest a system that scans dynamic network information in real time, scores vulnerability of network devices, generates all potential attack paths, and visualizes them using attack graph. We implemented the proposed algorithm based attack graph; and we demonstrated that it can be applicable in MTD concept based defense system by simulating on dynamic virtual network environment with SDN.

• Smart Media Journal
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• v.4 no.4
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• pp.24-32
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• 2015

Recently, SDN is actively used as datacenter networks and gradually increase its applied areas. Along with this change of networking environment, research of deploying network security systems on SDN becomes highlighted. Especially, systems for detecting network flooding attacks by monitoring every packets through ports of OpenFlow switches have been proposed. However, because of the centralized management of a SDN controller which manage multiple switches, it may be substantial overhead that the attack detection system continuously monitors all the flows. In this paper, a sampling based network flooding attack detection and prevention system is proposed to reduce the overhead of monitoring packets and to achieve reasonable functionality of attack detection and prevention. The proposed system periodically takes sample packets of network flows with the given sampling conditions, analyzes the sampled packets to detect network flooding attacks, and block the attack flows actively by managing the flow entries in OpenFlow switches. As network traffic sampler, sFlow agent is used, and snort, an opensource IDS, is used to detect network flooding attack from the sampled packets. For active prevention of the detected attacks, an OpenDaylight application is developed and applied. The proposed system is evaluated on the local testbed composed with multiple OVSes (Open Virtual Switch), and the performance and overhead of the proposed system under various sampling condition is analyzed.

• Electronics and Telecommunications Trends
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• v.29 no.6
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• pp.93-101
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• 2014

기존 하드웨어 중심의 네트워크 인프라를 소프트웨어 중심으로 진화시켜 서비스 유연성과 비즈니스 민첩성을 제고시킬 수 있는 새로운 네트워크 기술로 소프트웨어 정의 네트워킹(SDN: Software-Defined Networking)과 네트워크 기능 가상화(NFV: Network Functions Virtualisation) 기술이 최근 각광을 받고 있다. 빠르게 상용화 단계에 접어든 소프트웨어 정의 네트워킹 기술과 달리, 네트워크 기능 가상화 기술은 표준화 단체를 통한 기술 논의 및 상위 표준문서 작업에 많은 노력이 집중됨에 따라 네트워크 기능 가상화 기술을 개발하고 검증하며 운용할 수 있는 실질적인 플랫폼 개발에 대한 요구가 꾸준히 제기되어 왔다. 본고에서는 최근 Linux Foundation의 Collaborative Project로 발표된 공개 소프트웨어 기반의 네트워크 기능 가상화 플랫폼 개발 프로젝트인 OPNFV(Open Platform for NFV)의 목적과 개발범위 그리고 향후 개발방향을 중심으로 소개한다.

• Electronics and Telecommunications Trends
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• v.31 no.1
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• pp.86-98
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• 2016

초연결 사회는 Information & Communication Technology(ICT)를 바탕으로 하는 만물인터넷 또는 사물인터넷으로 사람, 프로세스, 데이터, 사물이 서로 연결되어 지능화된 통신인프라를 통해 새로운 가치와 혁신의 창출이 가능해지는 사회로 변화하게 된다. 이러한 초연결 사회의 유무선 통신서비스를 단일 통신인프라에서 제공할 수 있는 기술이 필요하다. 이를 구현하기 위해서는 분산된 네트워크 장비들을 소프트웨어적으로 용이하게 통합운영 관리할 수 있는 Software Defined Networking(SDN) 기술과 컴퓨팅, 서버 스토리지 및 네트워크 자원을 가상화하고, 오픈 인터페이스를 통하여 소프트웨어적으로 네트워크 기능제어가 가능한 Network Functions Virtualization(NFV) 기술에 의한 지능형 융합 통신인프라가 매우 중요하다. 본고에서는 초연결 통신인프라를 위한 클라우드 컴퓨팅 가상화 기술, NFV 기술동향 및 NFV Use Cases에 대한 내용을 통하여 향후 초연결 서비스 제공을 위한 통신인프라 구축 방향을 제시하고자 한다.

• Annual Conference of KIPS
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• 2016.04a
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• pp.133-135
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• 2016

현재 클라우드 네트워크는 복잡성 및 거대한 규모로 인해 기존 네트워크와는 차별화된 양상을 보이고 있다. 하드웨어 기반 보안 장비로만 보안 서비스를 제공하기에는 한정적 자원을 고려하였을 때 한계가 있으며, 온 디맨드 서비스와 멀티 테넌시로 인한 동적인 네트워크 환경은 관리자가 외부의 보안 위협뿐만 아니라 내부의 위협도 고려해야하도록 만든다. 본 논문에서는 SDN과 NFV를 이용하여 언급한 문제점들을 해결하고, 효과적인 보안 서비스를 제공할 수 있는 방법론을 제시하도록 한다.

• Journal of Information Processing Systems
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• v.16 no.4
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• pp.896-914
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• 2020

With the rapid growth of network traffic, a large number of connected devices, and higher application services, the traditional network is facing several challenges. In addition to improving the current network architecture and hardware specifications, effective resource management means the development trend of 5G. Although many existing potential technologies have been proposed to solve the some of 5G challenges, such as multiple-input multiple-output (MIMO), software-defined networking (SDN), network functions virtualization (NFV), edge computing, millimeter-wave, etc., research studies in 5G continue to enrich its function and move toward B5G mobile networks. In this paper, focusing on the resource allocation issues of 5G core networks and radio access networks, we address the latest technological developments and discuss the current challenges for resource management in 5G.

• Annual Conference of KIPS
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• 2020.11a
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• pp.128-130
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• 2020

소프트웨어 정의 네트워킹(SDN)은 기존 네트워크의 컨트롤 기능을 컨트롤러에 중앙 집중화하여 프로그램 가능하며 유연한 네트워크 관리 방식을 제공한다. 컨트롤러-스위치 간 인터페이스 표준 기술인 OpenFlow에서는 스위치 내부의 플로우 테이블을 이용하여 네트워크에 접근하는 패킷을 처리한다. 하지만 OpenFlow 스위치에 주로 사용되는 TCAM의 부족한 용량으로 인해, 많은 트래픽이 발생하는 환경에서 플로우 테이블에 충분한 양의 플로우 엔트리를 설치하지 못하는 문제가 발생한다. 이 경우 플로우 테이블 오버플로우가 발생하는데, 네트워크에 새로이 진입하는 플로우를 위하여 기존의 플로우 엔트리를 방출시킬 필요가 있다. 이때, 활성화된 플로우 엔트리를 방출하게 되면 네트워크 컨트롤 오버헤드가 크게 증가할 위험이 있다. 따라서 오버플로우가 발생했을 때 어떤 플로우 엔트리를 방출시킬지 정하는 것이 중요하다. 이에 본 논문은 플로우 프로토콜 타입에 기반한 플로우 엔트리 방출 정책을 제안하여 효율적인 플로우 테이블 사용을 목표로 한다.

• Journal of Intelligence and Information Systems
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• v.22 no.1
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• pp.107-118
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• 2016

The advent of 5G mobile communications, which is expected in 2020, will provide many services such as Internet of Things (IoT) and vehicle-to-infra/vehicle/nomadic (V2X) communication. There are many requirements to realizing these services: reduced latency, high data rate and reliability, and real-time service. In particular, a high level of reliability and delay sensitivity with an increased data rate are very important for M2M, IoT, and Factory 4.0. Around the world, 5G standardization organizations have considered these services and grouped them to finally derive the technical requirements and service scenarios. The first scenario is broadcast services that use a high data rate for multiple cases of sporting events or emergencies. The second scenario is as support for e-Health, car reliability, etc.; the third scenario is related to VR games with delay sensitivity and real-time techniques. Recently, these groups have been forming agreements on the requirements for such scenarios and the target level. Various techniques are being studied to satisfy such requirements and are being discussed in the context of software-defined networking (SDN) as the next-generation network architecture. SDN is being used to standardize ONF and basically refers to a structure that separates signals for the control plane from the packets for the data plane. One of the best examples for low latency and high reliability is an intelligent traffic system (ITS) using V2X. Because a car passes a small cell of the 5G network very rapidly, the messages to be delivered in the event of an emergency have to be transported in a very short time. This is a typical example requiring high delay sensitivity. 5G has to support a high reliability and delay sensitivity requirements for V2X in the field of traffic control. For these reasons, V2X is a major application of critical delay. V2X (vehicle-to-infra/vehicle/nomadic) represents all types of communication methods applicable to road and vehicles. It refers to a connected or networked vehicle. V2X can be divided into three kinds of communications. First is the communication between a vehicle and infrastructure (vehicle-to-infrastructure; V2I). Second is the communication between a vehicle and another vehicle (vehicle-to-vehicle; V2V). Third is the communication between a vehicle and mobile equipment (vehicle-to-nomadic devices; V2N). This will be added in the future in various fields. Because the SDN structure is under consideration as the next-generation network architecture, the SDN architecture is significant. However, the centralized architecture of SDN can be considered as an unfavorable structure for delay-sensitive services because a centralized architecture is needed to communicate with many nodes and provide processing power. Therefore, in the case of emergency V2X communications, delay-related control functions require a tree supporting structure. For such a scenario, the architecture of the network processing the vehicle information is a major variable affecting delay. Because it is difficult to meet the desired level of delay sensitivity with a typical fully centralized SDN structure, research on the optimal size of an SDN for processing information is needed. This study examined the SDN architecture considering the V2X emergency delay requirements of a 5G network in the worst-case scenario and performed a system-level simulation on the speed of the car, radius, and cell tier to derive a range of cells for information transfer in SDN network. In the simulation, because 5G provides a sufficiently high data rate, the information for neighboring vehicle support to the car was assumed to be without errors. Furthermore, the 5G small cell was assumed to have a cell radius of 50-100 m, and the maximum speed of the vehicle was considered to be 30-200 km/h in order to examine the network architecture to minimize the delay.