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收集所有交通大學研究人員與學生個人或團體所發表之各項學術著作，涵蓋期刊論文、教師專書、學位論文等項。;;Collections of Publications of NCTU Researchers and Students Like Journal Papers and Thesis.

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Now showing 1 - 10 of 19

How NAT-Compatible Are VoIP Applications?
(2010-12-01)
Lin, Ying-Dar
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Tseng, Chien-Chao
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Ho, Cheng-Yuan
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Wu, Yu-Hsien
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資訊工程學系
Today, the Internet is very diversified, further complicating the classic NAT traversal problems. In order to solve these problems, there are many proposed methods classified into two categories. One enhances the NAT traversal techniques of applications, and the other tries to modify the behavior of NATs. In this article we focus on the former because NATs have been installed, and their behavior cannot be altered through endpoint users. Accordingly, in order to test NAT traversal techniques of five VoIP applications (Skype, MSN, Google Talk, X-Lite, and Linphone), three network topologies have been designed with two endpoints behind the same, different, or multilevel NATs. Through a series of experiments and from the experiment results, we observe that these VoIP applications use some traversal techniques, such as NAT mapped-address probe, peer discovery, path check, and relay first, proposed by STUN, TURN, and ICE to make a direct connection when endpoints are behind the same or different NATs with independent mapping rules. However, with multilevel NATs, no endpoints can establish a direct connection when they use the above mentioned techniques, even if hairpin behavior is supported by NATs.
To Call or To Be Called Behind NATs is Sensitive in Solving the Direct Connection Problem
(2011-01-01)
Ho, Cheng-Yuan
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Tseng, Chien-Chao
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Wang, Fu-Yu
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Wang, Jui-Tang
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Lin, Ying-Dar
In this article, we first depict the call-role sensitivity problem in Network Address Translation (NAT) traversal, and then propose an approach to resolving the problem. The problem is whether a direct connection can be found between two peers across NATs mainly depends on the NAT type at the caller's side. We propose the extra-candidate connectivity check where both peers initiate a direct connectivity check to eliminate the effect of the call role. We have implemented the extra-candidate connectivity check and conducted experiments with 18 different NATs. Experimental results show that our approach can indeed resolve the call-role sensitivity problem, and maximize the direct connectivity rate (DCR) which is improved by 18.71% from the original scheme.
NAT-Compatibility Testbed: An Environment to Automatically Verify Direct Connection Rate
(2011-01-01)
Ho, Cheng-Yuan
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Wang, Fu-Yu
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Tseng, Chien-Chao
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Lin, Ying-Dar
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資訊工程學系
In this article, an NAT-compatibility testbed is designed to automatically conduct the repeated experiments, collect the test results, and verify the direct connection rate (DCR) of any NAT traversal programs. Achieving a high DCR is important because using relays may unnecessarily increase the bandwidth cost, processing load of the relay servers, and the end-to-end packet delay. The NAT-compatibility testbed is constructed with 4 components: two peers, an automatic execution mechanism, NAT devices, and signaling/intermediate servers such as STUN, TURN, and SIP. It is also called the fully meshed testbed because the test result of all NAT combinations is a square. It measures the DCR of ICE, KeyStone, and PJNATH as 53.7%, 59.87%, and 50.93%, respectively. Experimental results show that asymmetric and unexpected direct connectivity check results occur in the real Internet. In order to enhance NAT traversal capability, the findings, like "port prediction" and "call-role sensitivity problem," are also described in the experimental results.
Bandwidth and Latency Aware Contribution Estimation in P2P Streaming System
(2014-09-01)
Ho, Cheng-Yun
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Huang, Ming-Hsiang
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Ho, Cheng-Yuan
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Tseng, Chien-Chao
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交大名義發表
In this article, a bandwidth and latency aware contribution estimation (BLACE) mechanism is proposed to enhance the efficiency of content distribution in a mesh peer-to-peer (P2P) streaming system. This is because the mesh P2P streaming system outperforms others in many aspects, but most content distribution mechanisms use only one of upload bandwidth and link latency as a factor, several contribution-aware schemes (CASs) just punish selfish peers, and some CASs only rearrange the content receiving order. Hence, the BLACE proposes a prevention way considering every peer\'s upload bandwidth, link latency, and the maximum playing delay of a stream at the same time to prioritize the content distribution. Moreover, BLACE is implemented on Coolstreaming with NS2 and experimental results show that BLACE could at the most shorten the receiving time about 15.44%, 13.94%, and 8.26%, and improve the whole performance about 7.05%, 2.81%, and 2.69% at the most, when it compares with the Coolstreaming, the Coolstreaming with bandwidth preference, and the Coolstreaming with latency preference, respectively.
Calibrating parameters and formulas for process-level energy consumption profiling in smartphones
(2014-09-01)
Lin, Ying-Dar
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Rattagan, Ekarat
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Lai, Yuan-Cheng
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Chang, Li-Pin
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Yo, Yun-Chien
Battery-powered mobile devices substantially constrain energy resources. Process-level energy profiling tools can identify the most energy-consuming process and detail the energy usage of hardware components. With the help of energy profiling tools, programmers can fine-tune the energy consumption of processes to extend battery lifetime. However, profiling tools are highly dependent on hardware and must be calibrated for each hardware platform. Furthermore, for any new hardware components, new energy estimation formulas must be created. To solve these two problems regarding off-the-shelf products, this work proposes a two-phase calibrating approach. The first phase reconstructs the power table with a power meter, while the second creates new energy estimation formulas using linear regression analysis. The accuracy of the calibrated tool was evaluated in five scenarios and its error ratio is proven to be below 10%, occasionally less than 5%. Hence, this proposed approach to energy consumption profiling represents a major step in off-the-shelf devices. (C) 2014 Elsevier Ltd. All rights reserved.
Creditability-based weighted voting for reducing false positives and negatives in intrusion detection
(2013-11-01)
Lin, Ying-Dar
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Lai, Yuan-Cheng
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Ho, Cheng-Yuan
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Tai, Wei-Hsuan
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資訊工程學系
False positives (FPs) and false negatives (FNs) happen in every Intrusion Detection System (IDS). How often they occur is regarded as a measurement of the accuracy of the system. Frequent occurrences of FPs not only reduce the throughput of an IDS as FPs block the normal traffic and also degrade its trustworthiness. It is also difficult to eradicate all FNs from an IDS. One way to overcome the shortcomings of a single IDS is to employ multiple IDSs in its place and leverage the different capabilities and domain knowledge of these systems. Nonetheless, making a correct intrusion decision based on the outcomes of multiple IDSs has been a challenging task, as different IDSs may respond differently to the same packet trace. In this paper, we propose a method to reduce FPs and FNs by applying a creditability-based weighted voting (CWV) scheme to the outcomes of multiple IDSs. First, the CWV scheme evaluates the creditability of each individual IDS by monitoring its response to a large collection of pre-recorded packet traces containing various types of intrusions. For each IDS, our scheme then assigns different weights to each intrusion type according to its FP and FN ratios. Later, after their operations, the outcomes of individual IDSs are merged using a weighted voting scheme. In benchmarking tests, our CWV-based multiple IDSs demonstrated significant improvement in accuracy and efficiency when compared with multiple IDSs employing an ordinary majority voting (MV) scheme. The accuracy is the percentage of whole traces that are determined accurately, while the efficiency indicates that the voting algorithm performs better on reducing both FP and FN ratios. The CWV scheme achieved 95% accuracy and 94% efficiency while the MV scheme produced only 66% accuracy and 41% efficiency; the average percentages of FP/FN reduction were 21% and 58% respectively. (C) 2013 Elsevier Ltd. All rights reserved.
Booting, browsing and streaming time profiling, and bottleneck analysis on android-based systems
(2013-07-01)
Lin, Ying-Dar
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Ho, Cheng-Yuan
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Lai, Yuan-Cheng
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Du, Tzu-Hsiung
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Chang, Shun-Lee
Android-based systems perform slowly in three scenarios: booting, browsing, and streaming. Time profiling on Android devices involves three unique constraints: (1) the execution flow of a scenario invokes multiple software layers, (2) these software layers are implemented in different programming languages, and (3) log space is limited. To compensate for the first and second constraints, we assumed a staged approach using different profiling tools applied to different layers and programming languages. As for the last constraint and to avoid generating enormous quantities of irrelevant log data, we began profiling scenarios from an individual module, and then iteratively profiled an increased number of modules and layers, and finally consolidated the logs from different layers to identify bottlenecks. Because of this iteration, we called this approach a staged iterative instrumentation approach. To analyze the time required to boot the devices, we conducted experiments using off-the-shelf Android products. We determined that 72% of the booting time was spent initializing the user-space environment, with 44.4% and 39.2% required to start Android services and managers, and preload Java classes and resources, respectively. Results from analyzing browsing performance indicate that networking is the most significant factor, accounting for at least 90% of the delay in browsing. With regard to online streaming, networking and decoding technologies are two most important factors occupying 77% of the time required to prepare a 22 MB video file over a Wi-Fi connection. Furthermore, the overhead of this approach is low. For example, the overhead of CPU loading is about 5% in the browsing scenario. We believe that this proposed approach to time profiling represents a major step in the optimization and future development of Android-based devices. (c) 2013 Elsevier Ltd. All rights reserved.
Can: A context-aware NAT traversal scheme
(2013-07-01)
Tseng, Chien-Chao
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Lin, Chia-Liang
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Yen, Li-Hsing
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Liu, Jyun-Yan
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Ho, Cheng-Yuan
Network Address Translation (NAT) is a technique commonly used to share one public IPv4 address among several hosts located behind a NAT device. NAT devices typically block session requests originating from outside, causing NAT traversal problem that prevents the establishment of peer-to-peer (P2P) sessions. There have been many proposals for the NAT traversal problem. However, existing methods induce high connectivity check delay and resource demand when finding a communicating path, calling for a routine that determines the path best suited for a given pair of communicating peers. This study proposes CAN, a Context-Aware NAT traversal scheme which gathers and exchanges network-context information to find the most appropriate path for two communicating peers behind NAT devices. We have implemented CAN and conducted extensive experiments with off-the-shelf NAT devices to compare the performance of CAN with Interactivity Connectivity Establishment (ICE), the most acknowledged approach to creating a session across NATs. Experimental results show that CAN outperforms ICE in terms of direct communication ratio, connectivity check delay and message overload when checking connectivity. (c) 2013 Elsevier Ltd. All rights reserved.
A cross-layer approach for real-time multimedia streaming on wireless peer-to-peer ad hoc network
(2013-01-01)
Kuo, Jun-Li
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Shih, Chen-Hua
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Ho, Cheng-Yuan
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Chen, Yaw-Chung
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資訊工程學系
Peer-to-peer (P2P) live streaming over mobile ad hoc network (MANET) is a state-of-the-art technique for wireless multimedia applications, such as entertainments and disaster recovery. The peers share the live streaming over MANET via multi-hop wireless link, so an efficient data delivery scheme must be required. However, the high churn rate and the frequent mobility baffle the P2P membership management and overlay maintenance. The unreliable wireless connection of MANET leads to the difficulties of large-scale and real-time streaming distribution, and a lack of overlay proximity leads to the inefficient streaming delivery. We present a cross-layer design for P2P over MANET to manage and maintain the overlay, and select efficient routing path to multicast media streams. Our proposed scheme (COME-P2P) integrates both P2P DHT-based lookup and IPv6 routing header to improve the delivery efficiency. Through the cross-layer design, the low layer detects mobility for informing high layer to refine the finger table, and high layer maintains the efficient multicast path for informing low layer to refine the routing table. How to keep stable routing paths for live streaming via IPv6 routing is the main contribution of this paper. The overlay proximity can shorten routing propagation delay, and the hop-by-hop routing can avoid the traffic bottleneck. Through the mathematical analysis and simulation results, COME-P2P can be demonstrated to achieve high smoothness and reduce signaling overhead for live streaming. (C) 2012 Elsevier B.V. All rights reserved.
Media-Independent Handover Design for Seamless Mobility in Heterogeneous WiMAX/Wi-Fi Networks
(2012-10-01)
Shih, Chen-Hua
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Kuo, Jun-Li
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Ho, Cheng-Yuan
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Chen, Yaw-Chung
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友訊交大聯合研發中心
As we are moving toward next generation wireless networks, we are facing the integration of heterogeneous access networks. The main challenge is to provide mobile users moving freely across different radio access technologies with satisfactory quality of services for a variety of applications. Consequently, the seamless roaming over heterogeneous networks is an important concern. To minimize the disruption to the ongoing session when a mobile user is moving from one access network to another, we propose a framework that integrates IEEE 802.11 WLANs and IEEE 802.16 WMANs based on the IEEE 802.21, so-called Media Independent Handover (MIH), to facilitate both homogeneous and heterogeneous handovers. Both numerical analysis and simulation results show that seamless roaming between WLAN and WMAN can be achieved and much better performance can be obtained compared with the IEEE 802.21 standard approach.

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