• Journal of KIISE:Information Networking
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• v.32 no.6
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• pp.745-752
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• 2005

BGP is a unique routing protocol in broadband internet. It chooses routing paths considering internet hierarchy and local policies. As BGP routers selectively bypass routing information to a subset of neighboring BGP routers, connectivity by way of a series of links between source and destination nodes does not mean reachability of routing information of the two. In emergency when BGP routers or links over wide range are not available, BGP routers have to use links that are not normally used to keep reachability. This paper listed out the requirements for BGP backup routing and proposed a routing solution that hides most demerits in currently published ones. The proposed backup operates in three tiers according to network damage. Under this rule, BGP routers use tier-0 routing paths at normal. If networks are impaired, they choose tier-1 paths. If networks are seriously damaged, tier-2 paths are allowed to use. Also this paper proves that the proposed backup guarantees stability and safeness. As results, the proposed backup is very adaptive to light network damages as well as serious ones and provides strong routing reachability at all times.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.28 no.10B
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• pp.927-937
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• 2003

Network based VPN(Virtual Private Network) using MPLS(Multiprotocol Label Switching) technology is regarded as a good solution for intranets or extranets because of the low cost and the flexibility of the service provision. In this paper, we describea mechanism that allows the VPN users to move from one site to another site of the VPN network based on the BGP-E MPLS technology. This mechanism is designed for and implemented on PE(Provider Edge) routers of the backbone network. PE routers connected to the VPN sites establish a new MPLS path to the mobile node after they detect movement of the mobile VPN node. The new location may belong to the same VPN or to different VPN. We designed VPN management and control functions of the PE routers in order to interface with the Mobile IP protocol. The pilot implementation and performance measurement were carried out on a testbed.

• Electronics and Telecommunications Trends
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• v.15 no.5 s.65
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• pp.41-48
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• 2000

MPLS(Multiprotocol Label Switching)를 이용한 IP 기반의 VPN은 고수익을 원하는 서비스제공자들과 저비용을 원하는 기업들에게 인트라넷(intranet)과 익스트라넷(extranet)의 해결책으로서 많은 관심을 끌고 있다. MPLS VPN에 대한 표준화는 IETF에서 추진되고 있는데, BGP multiprotocol extension(BGP-E)이라는 프로토콜을 이용하는 구조와 Virtual Router(VR)라는 개념을 이용하는 구조가 제안되었다. BGP-E 방식은 시스코에 의해 제안되어 RFC2547로 채택되었다. 이 방식에서는 BGP-E를 이용하여 도달성과 멤버쉽 정보를 PE간에 교환한다. VR 방식은 노텔과 루슨트를 중심으로 여러 기업들이 지지하고 있고 드래프트 형태로 작업중이다. 이 방식에서는 PE들에 VPN별로 VR들을 배치하고 같은 VPN에 속하는 VR들끼리 기존의 라우팅 프로토콜을 이용하여 라우팅 정보를 교환한다. 두 방식의 근본적 차이는 도달성과 멤버쉽 메커니즘의 분리 여부이다. 세계적으로 이름 있는 통신 회사들이 경쟁적으로 MPLS 시스템을 개발하고 있는 상황에서 MPLS VPN 기술도 빠르게 시장에 확산될 것으로 전망된다. 그러나 서로 다른 기술적 접근을 하고 있는 서비스제공자들간의 MPLS VPN에 대한 호환성은 시급히 풀어야 할 숙제로 남아 있다.

• The Journal of Engineering Research
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• v.2 no.1
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• pp.83-94
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• 1997

This paper documents how the user modeling shell BGP-MS is adapted to suit the user-modeling requirements of the Intelligent Dialog Model(IDM) and descriebes the background information about building a user model framework within BGP-MS, i.e. how to configure the shell system with application specific needs.

• Journal of Communications and Networks
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• v.9 no.4
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• pp.490-498
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• 2007

BGP route flap damping(RFD) was anecdotally considered to be a key contributor to the stability of the global Internet inter-domain routing system. However, it was recently shown that RFD can incorrectly suppress for substantially long periods of time relatively stable routes, i.e., routes that only fail occasionally. This phenomenon can be attributed to the complex interaction between BGP path exploration and how the RFD algorithm identifies route flaps. In this paper we identify a distinct characteristic of BGP path exploration following a single network event such as a link or router failure. Based on this characteristic, we distinguish BGP route updates during BGP path exploration from route flaps and propose a novel BGP route flap damping algorithm, RFD+. RFD+ has a number of attractive properties in improving Internet routing stability. In particular, it can correctly suppress persistent route flaps without affecting routes that only fail occasionally. In addition to presenting the new algorithm and analyzing its properties, we also perform simulation studies to illustrate the performance of the algorithm.

• Journal of Communications and Networks
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• v.14 no.3
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• pp.336-345
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• 2012

Autonomous system (AS) business relationships and their inference have been widely studied by network researchers in the past. An important application of inferred AS relationships can be the prediction of AS paths between a source and destination AS within a model. However, besides knowing the topology and inferred AS relationships, AS path prediction within a model needs to be understood in order for us to know how we can derive border gateway protocol (BGP) policies from AS relationships. In this paper, we shed light onto the predictive capabilities of AS relationships by investigating whether they can be translated into BGP policies such that inferred AS paths are consistent with real AS paths, e.g., paths observed from BGP routing tables. Our findings indicate that enforcing constraints such as the well-known valley-free property and the widely assumed preference of customer routes always results in a very low consistency for AS path inference. In addition, this is true irrespective of whether customer, peer, or provider routes are preferred. Apparently, applying such constraints eliminates many "correct" paths that are observed in BGP routing tables and that are propagated in a simple shortest path model where AS relationships are ignored. According to our findings, deriving BGP routing policies for predicting with high accuracy AS paths in a model directly from AS relationships is still difficult.

• ETRI Journal
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• v.24 no.2
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• pp.97-108
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• 2002

Optical Border Gateway Protocol (OBGP) is an extension to BGP for Optical Cross Connects (OXCs) to automatically setup multiple direct optical lightpaths between many different autonomous domains. With OBGP, the routing component of a network may be distributed to the edge of the network while the packet classification and forwarding is done in the core. However, it is necessary to analyze the stable convergence functions of OBGP in case of lightpath failures. In this paper, we first describe the architecture of the OBGP model and analyze the potential problems of OBGP, e.g., virtual BGP router convergence behavior in the presence of lightpath failure. We then propose an OBGP convergence model derived from an inter-AS (Autonomous System) relationship. The evaluation results show that the proposed model can be used for a stable OBGP routing policy and OBGP routing convergence under lightpath failures of the optical Internet.

• Proceedings of the Korea Information Processing Society Conference
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• 2003.05b
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• pp.1309-1312
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• 2003

VPN(Virtual Private Network)은 공중망(Public Network)을 통해서 사설망(Private Network) 서비스를 제공해준다. VPN의 발달과 더불어 여러 서비스를 제공하기 위해서는 VPN의 멀티캐스트 지원이 필수적이라 할 수 있다. 하지만 VPN에서 멀티캐스트를 제공하기 위해서는 많은 제약사항들이 존재한다. 본 논문에서는 이러한 제약사항을 고려하여 PE(Provider Edge)노드만으로 Tree를 구성하고 BGP-E를 통하여 멀티캐스트 정보를 공유하는 BGP-E기반 MPLS VPN의 멀티캐스트 방법을 제안한다.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.10 no.1
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• pp.65-73
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• 2006

Network based VPN(Virtual Private Network) using MPLS(Multiprotocol Label Switching) technology, called PE(Provider Edge router) based MPLS VPN, is regarded as a good solution for intranets or ext3nets because of the low cost and the flexibility of the service provision. In this paper, we describe a mechanism that allows the VPN users to move from one site to another site of the VPN network based on the BGP-E MPLS technology. This mechanism is designed for PE(Provider Edge) routers of the backbone network. PE routers connected to the VPN sites establish a new MPLS path to the mobile node after they detect movement of the mobile VPN node. The new location may belong to the same VPN or to different VPN. We desisted VPN management and control functions of the PE routers in order to interface with the Mobile IP protocol and support the QoS mechanism. The pilot implementation and performance measurement were carried out on a simulation using COVERS tool.

• Journal of The Korean Association For Science Education
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• v.26 no.4
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• pp.568-580
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• 2006

The purpose of this study was to investigate the brain activities by 4-types of Generating Process of Scientific Emotion (GPSE) in the hypothesis-generating biological phenomena by using fMRI. Four-types of GPSE were involved in the Basic Generating Process (BGP), Retrospective Generating Process (RGP), Cognitive Generating Process (CGP) and Attributive Generating Process (AGP). For this study, we made an experimental design capable of validating the 4-types of generating process (e.g. BGP, RGP, CGP and AGP), and then measured BOLD signals of 10 pre-service teachers' brain activities by 3.0T fMRI system. Subjects were 10 healthy females majoring in biology education. As a result, there were clear differences among 4-types of GPSE. Brain areas activated by BGP were at right occipital lobe (BA 17), at left thalamus and left parahippocampal gyrus, while in the case of RGP, at left superior parietal lobe (BA 8, 9), at left pulvinar and left globus pallidus were activated. Brain areas activated by CGP were the right posterior cingulate and left medial frontal gyrus (BA 6). In the case of AGP, the most distinctively activated brain areas were the right medial frontal gyrus (BA 8) and left inferior parietal lobule (BA 40). These results would mean that each of the 4-types of GPSE has a specific neural networks in the brain, respectively. Furthermore, it would provide the basis of brain-based learning in science education.