가상팀의 지식네트워크, IT 활용, 성과 간의 관계에 관한 연구

신경식(Kyung Shik Shin),서아영(A Young Suh) 한국경영학회 2009 經營學硏究 Vol.38 No.1

A virtual team is defined as a group of people that works across space, time, and organizational boundaries with links strengthened by the diverse computer-mediated communication media. By forming virtual teams, people can easily collaborate with other people and acquire information and knowledge from anywhere and at anytime. However, managing virtual teams is far more challenging than managing traditional teams because ad hoc virtual teams may engage in a lower level of social interacts and supports than their counterparts in face-to-face environments. The problem of how to manage social relationships among virtual team members to increase their performance is considered to be very pivotal and still remains unsolved. Through the lens of social networks, this study examines the following specific questions: (1) to what extent should ad hoc virtual teams maintain internal cohesion; (2) whether do virtual team members’ external bridging ties guarantee the higher level of team performance; and (3) how does IT play the role in balancing and harmonizing internal cohesion and external bridging ties for increasing the performance of a virtual team. We investigate these questions with the specific type of social networks; the knowledge networks which contain knowledge or task-related intelligence in the networks. These knowledge networks contain the collective competencies that enable organizational members to produce products and services. By examining the influence of knowledge networks of virtual teams on their performance, this study aims to reveal how to manage knowledge network among members to maximize the performance of a virtual team. The contributions of this study are three-fold. First, we conceptually clarify the properties of knowledge networks that individuals maintain within and outside their work groups: network density and group-level structural holes. Next, by integrating social network theory and CMC related theories, we develop a theoretical framework linking knowledge networks, IT use, and team performance. Third, we examine the interplay among the research constructs and elucidate a complex phenomenon in relations to the forming and managing knowledge networks of a virtual team, which is in short supply in the current literature. The proposed model was tested with 172 consultants and 42 virtual teams in 5 global consulting companies in Korea. The study found that increasing network intra-group network density was crucial for better team performance. On the contrary, increasing extra-group structural holes decreased the team performance, contradicting the prevailing wisdom. The most important standpoint is that the effect of knowledge network of virtual teams varied along the level of IT use that is related to communal CMC such as group ware or group decision support systems (GDSS). This study is meaningful in that it examined how to manage knowledge network by integrating social network theory and computer-mediation communication theory, and by analyzing the moderating effect between knowledge network and IT use in the context of virtual teams. Based on these findings, the study suggests that optimal knowledge network configurations to maximize the performance of a virtual team should be considered along with the IT use.

Virtual Network Mapping Algorithm Based on Load Balancing

Ming Jiang,Xijie Tang,Min Zhang,Ziyang Li 보안공학연구지원센터 2016 International Journal of Grid and Distributed Comp Vol.9 No.9

Recent studies for network virtualization have shown a promising way to overcome the Internet ossification. The one of the key issues in network virtualization is a virtual network mapping problem, i.e., mapping a virtual network to the physical network. The situations of dynamic arrivals of virtual network request and the limited life cycle of the virtual networks pose significant challenges to the virtual network mapping problem. A balance between the resource allocation of the physical network and the number of mapped virtual networks. In this paper, we have considered the time characteristics that virtual network requests when mapping algorithms so as to achieve the objective that the node load and link load can simultaneously reach a balance. Giving full consideration to mutual restraints of time and resources, we propose a two-dimensional discrete weighted model based on time and resources, and establish a mathematical programming model of minimizing the degree of two-dimensional load balancing. Moreover, we devise a VN embedding algorithms LB-VNE. Simulation experiments show that the proposed algorithms can increase the acceptance ratio and the revenue by the substrate network in the long term.

Isolation Schemes of Virtual Network Platform for Cloud Computing

( Sungwon Ahn ),( Shinhyoung Lee ),( Seehwan Yoo ),( Daeyoung Park ),( Dojung Kim ),( Chuck Yoo ) 한국인터넷정보학회 2012 KSII Transactions on Internet and Information Syst Vol.6 No.11

Network virtualization supports future Internet environments and cloud computing. Virtualization can mitigate many hardware restrictions and provide variable network topologies to support variable cloud services. Owing to several advantages such as low cost, high flexibility, and better manageability, virtualization has been widely adopted for use in network virtualization platforms. Among the many issues related to cloud computing, to achieve a suitable cloud service quality we specifically focus on network and performance isolation schemes, which ensure the integrity and QoS of each virtual cloud network. In this study, we suggest a virtual network platform that uses Xen-based virtualization, and implement multiple virtualized networks to provide variable cloud services on a physical network. In addition, we describe the isolation of virtual networks by assigning a different virtualized network ID (VLAN ID) to each network to ensure the integrity of the service contents. We also provide a method for efficiently isolating the performance of each virtual network in terms of network bandwidth. Our performance isolation method supports multiple virtual networks with different levels of service quality.

라우터 가상화 환경에서의 10G 이더넷 카드를 위한 네트워크 성능 분석

이치영(Chiyoung Lee),김도중(Dojung Kim),이종원(Jong-Won Lee),유혁(Hyuck Yoo) 한국정보과학회 2011 정보과학회논문지 : 정보통신 Vol.38 No.6

가상 네트워크는 논리적인 네트워크로, 다수의 가상 네트워크가 하나의 물리적 자원을 공유하여 동작한다. 따라서 가상 네트워크는 물리적인 네트워크의 구축에 비해 적은 비용으로 네트워크를 구축할 수 있다. 이러한 가상 네트워크를 구축하기 위해 요구되는 요소 중의 하나가 가상 라우터이다. 최근에는 고성능 PC 기반 플랫폼 상에서 가상 라우터를 구현하려는 연구도 진행되고 있다. 가상 라우터에서는, 한 가상 라우터의 동작 상태에 의해, 자원을 공유하고 있는 다른 가상 라우터가 영향을 받지 않아야 한다. 이러한 고립을 제공하기 위해 시스템 가상화 기술을 사용한다. 하지만 가상화 기술은 가상화에 따른 I/O 성능 열화의 문제가 있다. 특히, 라우터에서는 패킷의 송수신에 따른 I/O 작업이 많기 때문에, 이 I/O 성능 문제를 반드시 해결해야 한다. 본 논문에서는 가상 라우터 간의 고립을 보장하면서 가상화에 따른 I/O 오버헤드를 극복하기 위하여, Xen 기반 SR-IOV 기술을 적용한다. 그리고 실험을 통하여 SR-IOV 기술이 가상 라우터의 성능 향상에 효과가 있음을 보인다. 또한, 구축한 가상 라우터 상에서의 네트워크 성능을 측정하고 이를 분석한다. 이를 통해, 가상화 오버헤드 외에, 라우팅 과정과 멀티 코어 환경의 동기화 작업이 가상 라우터 성능 저하의 주요 원인임을 보인다. A virtual network is a kind of a logical network, and several virtual networks shares common physical resources. Therefore, compared to implement a physical network, a virtual network has a merit to be efficiently implemented in cost. A virtual router is a key component to implement virtual networks. Recently, researches of virtual routers on high performance commodity HW have been conducted. To support stable virtual networks, each virtual router does not affected by other virtual routers on the same physical platform. Generally, server virtualization techniques can be used to support isolation among virtual routers. However, the virtualization technique shows low I/O performance due to virtualization overhead. Because routers have executed many I/O operations to receive and transmit packets, the I/O overhead in virtualization should be avoided to implement high performance virtual routers This paper implements the Xen-based virtual router for isolation among routers, and reduces the virtualization overheads using SR-IOV to improve the I/O performance. And we show the performance effects by SR-IOV through an experiment. Also, we measure and analyze the performance of our virtual router. In here, We certificate a fact that the routing process and multi-core environment are reasons of the low network performance in the virtual router. This fact will be a foundation to develop some methods for network performance improvement in the virtual router.

Design of an Efficient Method for Identifying Virtual Machines Compatible with Service Chain in a Virtual Network Environment

Hyeonseok Oh,Daeun Yu,Yoon-Ho Choi,Namgi Kim 보안공학연구지원센터 2014 International Journal of Multimedia and Ubiquitous Vol.9 No.11

With advancements in network technologies, network virtualization has been proposed to efficiently provide a large number of services and flexible management by utilizing limited resources over existing networks as much as possible. Network virtualization has been proposed as a new paradigm for networks, as it simplifies complicated network configurations for convenient maintenance through the maximum utilization of limited network resources. However, problems have arisen due to network virtualization, such as how to assign real network components that are compatible with virtual network components over a large number of virtual machines existing in a network. In particular, the service-chaining concept—where a network flow only passes through needed services—has been newly introduced by combining the recently highlighted Software-Defined Network with a virtualization concept called Network Function Virtualization. As a result, studies on which virtual machines are selected and how to connect them have increased ever more. Accordingly, this paper aims to identify virtual machines that are compatible with service chaining in a virtual network environment where virtual machines are dispersed, and it proposes a method of how to create a path by connecting virtual machines.

Providing survivability for virtual networks against substrate network failure

( Ying Wang ),( Qingyun Chen ),( Wenjing Li ),( Xuesong Qiu ) 한국인터넷정보학회 2016 KSII Transactions on Internet and Information Syst Vol.10 No.9

Network virtualization has been regarded as a core attribute of the Future Internet. In a network virtualization environment (NVE), multiple heterogeneous virtual networks can coexist on a shared substrate network. Thus, a substrate network failure may affect multiple virtual networks. In this case, it is increasingly critical to provide survivability for the virtual networks against the substrate network failures. Previous research focused on mechanisms that ensure the resilience of the virtual network. However, the resource efficiency is still important to make the mapping scheme practical. In this paper, we study the survivable virtual network embedding mechanisms against substrate link and node failure from the perspective of improving the resource efficiency. For substrate link survivability, we propose a load-balancing and re-configuration strategy to improve the acceptance ratio and bandwidth utilization ratio. For substrate node survivability, we develop a minimum cost heuristic based on a divided network model and a backup resource cost model, which can both satisfy the location constraints of virtual node and increase the sharing degree of the backup resources. Simulations are conducted to evaluate the performance of the solutions. The proposed load balancing and re-configuration strategy for substrate link survivability outperforms other approaches in terms of acceptance ratio and bandwidth utilization ratio. And the proposed minimum cost heuristic for substrate node survivability gets a good performance in term of acceptance ratio.

Virtual Network Embedding with Multi-attribute Node Ranking Based on TOPSIS

( Shuiqing Gong ),( Jing Chen ),( Siyi Zhao ),( Qingchao Zhu ) 한국인터넷정보학회 2016 KSII Transactions on Internet and Information Syst Vol.10 No.2

Network virtualization provides an effective way to overcome the Internet ossification problem. As one of the main challenges in network virtualization, virtual network embedding refers to mapping multiple virtual networks onto a shared substrate network. However, existing heuristic embedding algorithms evaluate the embedding potential of the nodes simply by the product of different resource attributes, which would result in an unbalanced embedding. Furthermore, ignoring the hops of substrate paths that the virtual links would be mapped onto may restrict the ability of the substrate network to accept additional virtual network requests, and lead to low utilization rate of resource. In this paper, we introduce and extend five node attributes that quantify the embedding potential of the nodes from both the local and global views, and adopt the technique for order preference by similarity ideal solution (TOPSIS) to rank the nodes, aiming at balancing different node attributes to increase the utilization rate of resource. Moreover, we propose a novel two-stage virtual network embedding algorithm, which maps the virtual nodes onto the substrate nodes according to the node ranks, and adopts a shortest path-based algorithm to map the virtual links. Simulation results show that the new algorithm significantly increases the long-term average revenue, the long-term revenue to cost ratio and the acceptance ratio.

가상화된 SDN에서 효과적인 자원 활용을 위한 LISP 기반 IP 주소 가상화 기법

고영근(Youngkeun Go),양경식(Gyeongsik Yang),유봉열(Bong-yeol Yu),유혁(Chuck Yoo) Korean Institute of Information Scientists and Eng 2016 정보과학회논문지 Vol.43 No.12

Network virtualization is a technique that abstracts the physical network to provide multiple virtual networks to users. Virtualized network has the advantage to offer flexible services and improve resource utilization. In SDN architecture, network hypervisor serves to virtualize the network through address virtualization, topology virtualization and policy virtualization. Among them, address virtualization refers to the technique that provides an independent address space for each virtual network. Previous work divided the physical address space, and assigned an individual division to each virtual network. Each virtual address is then mapped one-to-one to a physical address. However, this approach requires a lot of flow entries, thus making it disadvantageous. Since SDN switches use TCAM (Ternary Contents Addressable Memory) for the flow table, it is very important to reduce the number of flow entries in the aspect of cost and scalability. In this paper, we propose a LISP based address virtualization, which separates address spaces for the physical and virtual addresses and transmits packet through tunneling, in order to resolve the limitation of the previous studies. By implementing a prototype, we show that the proposed scheme provides better scalability.

A Prototype Virtual Network Embedding System using OpenStack

Yukinobu Fukushima,Kohei Sato,Itsuho Goda,Heung-Gyoon Ryu,Tokumi Yokohira 대한전자공학회 2017 IEIE Transactions on Smart Processing & Computing Vol.6 No.1

Network virtualization enables us to make efficient use of resources in a physical network by embedding multiple virtual networks in the physical network. In this paper, we develop a prototype of a virtual network embedding system. Our system consists of OpenStack, which is an open source cloud service platform, and shell scripts. Because OpenStack does not provide a quality of service control function, we realize bandwidth reservation for virtual links by making use of the ingress policing function of Open vSwitch, which is a virtual switch used in OpenStack. The shell scripts in our system automatically construct the required virtual network on the physical network using the OpenStack command-line interface, and they reserve bandwidth for virtual links using the Open vSwitch command. Experimental evaluation confirms that our system constructs the requested virtual network and appropriately allocates node and link resources to it.

서울특별시 네트워크 RTK 시스템의 NTRIP 데이터 전송 및 Virtual RINEX의 활용

곽인선,남대현,권재현 대한공간정보학회 2010 Spatial Information Research Vol.18 No.5

Since January 2009, Seoul Metro Government(SMG) is operating own Network RTK Systems connecting four(4) GNSS Reference Stations which are installed inside Seoul Metro City area. SMG is currently providing VRS data service via wireless internet for Network-RTK and RINEX data observed from GNSS Reference Stations. This paper will discuss utilization of data available from SMG Network-RTK System for various applications, and present the test results on practicalities of Virtual RINEX data. For the utilization of data available from SMG Network- RTK system, 1)NTRIP data delivery of GNSS realtime observables streaming and converting to RINEX at receiving side, 2) monitoring deformation of bulky structures using GNSS observation were discussed. In addition to those discussion, 3) broadcasting VRS correction data for job site via radio modem after acquiring such correction data on-line using NTRIP based GNSS Internet Radio from SMG Network-RTK System were introduced. For the test results on practicalities of Virtual RINEX data, 1) the post-processing results of the GNSS observation data on a certain point with GNSS Reference Station data have been compared to the post-processing results of Virtual RINEX data on the same point generated from SMG Network-RTK System, and 2) VRS RTK positioning results for a certain point and post-processing results of Virtual RINEX data for the point were compared. The results showed only a few mm difference, and the high possibility for using Virtual RINEX data for post-processing applications. 서울특별시는 2009년 초 4개의 GNSS 고정 기준국을 설치하고 네트워크 RTK 시스템을 구축하여 현재 운영 중에 있다. 현재는 무선인터넷을 이용한 VRS 측위 서비스와 후처리를 위한 고정 기준국 RINEX 데이터를 제공하고 있다. 본 연구에서는 서울특별시 네트워크 RTK 시스템의 활용성 증대 방안을 검토하고, Virtual RINEX 실용성 검토를 위한 실험을 수행하였다. 네트워크 RTK 시스템의 활용 다양화를 위한 검토는 1) GNSS 고정 기준국의 관측 데이터를 NTRIP을 통하여 타기관의 사용자 시스템으로 실시간 전송하고 수신측 기관에서는 이를 RINEX 데이터로 변환 생성하는 방법, 2) GNSS를 이용하여 주요 장대 시설물의 변위를 모니터링 하는 방법을 검토하였다. 또한 3) NTRIP을 이용한 GNSS Internet Radio로 VRS 보정 데이터를 네트워크 RTK 시스템으로부터 수신하고 무선모뎀을 이용, 소규모 작업 지역을 대상으로 방송하여 RTK측위를 실시하는 방법을 소개 하였다. Virtual RINEX 실용성 검토를 위한 실험은 1) GNSS고정 기준국에서 관측한 기준국 데이터와 특정 지점에서 실제로 관측한 GNSS 관측 데이터로 후처리한 성과와 그 지점의 Virtual RINEX 데이터를 이동국 데이터로 한 후처리 성과를 비교하였다. 또한 2) 특정 지점에 대한 VRS RTK 측위 결과와 이동국 측위 지점에 대한 Virtual RINEX 데이터의 후처리 성과를 비교하였다. 그 결과, Virtual RINEX와 GPS 관측 성과는 거의 동일하여 향후 Virtual RINEX도 후처리 데이터로 사용할 수 있는 가능성을 확인하였고, VRS RTK 측위 성과는 Virtual RINEX 후처리 성과와 수 mm 이내 차이를 보여 산출된 성과가 거의 같음을 확인할 수 있었다.