• Information and Communications Magazine
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• v.30 no.3
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• pp.43-50
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• 2013

현존하는 프로토콜 중심의 네트워킹이 가지는 근본적인 한계를 인식하고 이를 소프트웨어-정의 네트워킹(Software Defined Networking: SDN)이라는 새로운 흐름으로 해소하자는 노력이 확산되고 있다. 즉 실험자들이 점차 복잡해지는 네트워킹 문제들을 논리적으로 집중화된 단순함으로 재편하여 손쉽게 해결하자는 것이다. 본 논문에서는 SDN에 기반한 미래형 서비스 실증을 위해 핵심적인 도구로 대두된 시험환경(또는 테스트베드)의 구축 방향과 사례를 살펴본다. 먼저 가상화되고 프로그램이 가능한 융합형 실험자원들을 다수의 실험자들이 공용하는 환경을 구축하고, 개별적으로 서비스 실증을 자유롭게 시도하는 전체 프레임워크를 제시한다. 특히 융합형 자원을 Rack 방식으로 구성하고 이를 연동하여 시험환경을 구축하는 추세에 따라, 독자적인 SmartX Rack을 사용한 SDN 기반 서비스 실증을 위한 시험환경 구축 사례를 설명한다.

• Electronics and Telecommunications Trends
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• v.28 no.5
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• pp.43-56
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• 2013

최근 대규모 데이터 센터 설립, 클라우드 컴퓨팅의 확산 등 ICT(Information and Communication Technology) 기반 다양한 비즈니스 요구 증가에 따라 SDN(Software Defined Networking)에 대한 관심이 크게 증가하고 있다. 본고에서는 망의 구성과 동작을 개방화하고 소프트웨어로 유연하게 인프라를 제어 및 관리할 수 있는 SDN 기술이 광통신망에 도입되어 구현될 때 요구되는 광통신의 핵심 요소 기술들의 동향을 분석한다. 그 중에서도 차세대 ROADM(Reconfigurable Optical Add/Drop Multiplexer) 기술, 100G급 이상의 라인 사이드 광트랜시버와 클라이언터 사이드 광트랜시버 기술, 변조방식과 전송속도를 유연하게 가변 할 수 있는 디지털 신호 처리 기술들의 현황 및 동향에 대해서 기술한다.

• Journal of Internet Computing and Services
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• v.23 no.5
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• pp.17-23
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• 2022

Network slicing is a promising paradigm and significant evolution for adjusting the heterogeneous services based on different requirements by placing dynamic virtual network functions (VNF) forwarding graph (VNFFG) and orchestrating service function chaining (SFC) based on criticalities of Quality of Service (QoS) classes. In system architecture, software-defined networks (SDN), network functions virtualization (NFV), and edge computing are used to provide resourceful data view, configurable virtual resources, and control interfaces for developing the modified deep reinforcement learning agent (MDRL-A). In this paper, task requests, tolerable delays, and required resources are differentiated for input state observations to identify the non-critical/critical classes, since each user equipment can execute different QoS application services. We design intelligent slicing for handing the cross-domain resource with MDRL-A in solving network problems and eliminating resource usage. The agent interacts with controllers and orchestrators to manage the flow rule installation and physical resource allocation in NFV infrastructure (NFVI) with the proposed formulation of completion time and criticality criteria. Simulation is conducted in SDN/NFV environment and capturing the QoS performances between conventional and MDRL-A approaches.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.13 no.2
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• pp.733-750
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• 2019

Software Defined Networking (SDN) is a new network paradigm, allowing administrators to manage networks through central controllers by separating control plane from data plane. So, one or more controllers must locate outside switches. However, this separation may cause delay problems between controllers and switches. In this paper, we therefore propose a Priority-based Scheduling policy for OpenFlow (PSO) to reduce the delay of some significant traffic. Our PSO is based on packet prioritization mechanisms in both OpenFlow switches and controllers. In addition, we have prototyped and experimented on PSO using a network simulator (ns-3). From the experimental results, PSO has demonstrated low delay for targeted traffic in the out-of-brand control network. The targeted traffic can acquire forwarding rules with lower delay under network congestion in control links (with normalized load > 0.8), comparing to traditional OpenFlow. Furthermore, PSO is helpful in the in-band control network to prioritize OpenFlow messages over data packets.

• Proceedings of the Korea Information Processing Society Conference
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• 2015.04a
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• pp.203-204
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• 2015

하나의 AP에 다수의 사용자가 연결되어 AP의 부하가 가중될 경우 해당 AP에 연결되어 있는 사용자들의 무선데이터 전송속도는 현저하게 떨어진다. 이를 방지하기 위해 본 논문에서는 SDN 기술을 사용하여 SDN 제어기에서 연결된 AP들의 부하분산을 지원하는 시스템을 제안하였으며, 해당 시스템은 SDN 제어기와 AP 그리고 안드로이드 스마트폰으로 구성되었다. 본 논문에서 제안하는 시스템을 지원하기 위해 각각의 AP들은 SDN 제어기와의 통신을 담당하는 SDN Agent를 설치한다. 또한 현재 이동통신단말기가 연결이 가능한 AP들의 목록을 작성하기 위해 이동통신 단말기에도 SDN Agent를 설치한다. SDN 제어기는 각각의 Agent로부터 받은 정보들을 통해 적합한 AP로 이동통신 단말기가 다시 연결될 수 있도록 한다. 본 논문에서는 제안한 시스템의 검증을 위해 실험환경을 구성하여 실험을 수행하였으며 효과적으로 동작하는 것을 확인하였다.

• KNOM Review
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• v.22 no.1
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• pp.30-41
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• 2019

MQTT protocol is one of open Publish / Subscribe systems for IoT information transmission. In this paper, we are proposing an algorithm to assign a subscriber, which dynamically participate in MQTT clustering system, to an appropriate broker. In MQTT systems with a centralized broker, there are losses of connectivity and messages between subscribers and brokers. In this paper, we addressed this issue for developing scalable open IoT systems and consider clustering MQTT brokers on the SDN infrastructure. In particular, this paper focuses on the problem of allocating subscribers to brokers in accordance with sharing brokers' topics to reduce brokers' load and communication cost in SDN based MQTT cluster. The Experimental results show that the proposed algorithm will reduce the load and the cost as compared to existing methods.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.39B no.6
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• pp.406-413
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• 2014

In recent years, various contents traffics are increasing according to the various internet connectable devices which have become contents provider. Because these contents traffics show different pattern from previous one, many researches for efficient contents delivery system are in progress. CCN(Contents Centric Network), one of the representative research subject, has inter operation problem with a current network because it has clean-state architecture. In this point of view, this paper suggests the SaNA(Service adaptive Network Architecture) for efficient contents delivery when it inter operates with current network architecture. SaNA is a convergence system which can be gradually applied to current network using CCN and SDN(Software Defined Network) which are core future internet technologies. Appling this system on the contents delivery service, it can increase the network bandwidth utilization by two times and decrease the contents delivery time by 1.7 times.

• KIPS Transactions on Computer and Communication Systems
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• v.6 no.11
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• pp.453-462
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• 2017

OpenDaylight is an SDN (Software Defined Networking) open source framework, which is popular in network fields recently. This paper analyzes the performance of a controller cluster architecture by focusing on distributed datastore and Raft leader election algorithm. In addition, we propose an enhanced version of Raft algorithm in order to improve the performance of distributed datastore by distributing shard leaders over controller cluster. This paper compares the conventional Raft algorithm with the proposed version of the Raft algorithm. Moreover, we compare the performance of distributed datastore according to shard roles such as leader and follower. Experimental results show that Shard leaders provide better performance than followers and Shard updating requests need to be distributed over multiple controllers. So, by using proposed version of Raft algorithm, controller performance can be improved. The details of the experiment results are cleary described.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.13 no.7
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• pp.3671-3689
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• 2019

Software defined networking brings unique security risks such as control plane saturation attack while enhancing the performance of wireless sensor networks. The attack is a new type of distributed denial of service (DDoS) attack, which is easy to launch. However, it is difficult to detect and hard to defend. In response to this, the attack threat model is discussed firstly, and then a DDoS attack prevention extension, called FuzzyGuard, is proposed. In FuzzyGuard, a control network with both the protection of data flow and the convergence of attack flow is constructed in the data plane by using the idea of independent routing control flow. Then, the attack detection is implemented by fuzzy inference method to output the current security state of the network. Different probabilistic suppression modes are adopted subsequently to deal with the attack flow to cost-effectively reduce the impact of the attack on the network. The prototype is implemented on SDN-WISE and the simulation experiment is carried out. The evaluation results show that FuzzyGuard could effectively protect the normal forwarding of data flow in the attacked state and has a good defensive effect on the control plane saturation attack with lower resource requirements.

• Information and Communications Magazine
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• v.31 no.6
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• pp.3-11
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• 2014

Mobile operators today face yet another critical challenge as technology lifecycle becomes increasingly short and also as heterogeneous and complex network becomes exceedingly expensive and difficult to manage. With extremely competitive market and demanding users, the overall revenue structure is expected to get worse. A network architecture based on software-defined networking (SDN) and virtualization techniques gives operators greater opportunity to build cost-effective and efficient alternative to the legacy. In this work we review our Carrier Cloud as a future mobile network infrastructure that exploits both SDN and NFV in order to increase the operator agility, reduce the cost, and even disrupt the vendor landscape. This new architecture will not be fully adopted by the conservative operators at once. Technological hurdles have to be overcome, and a clear understanding of operational differences must be preceded.