Browsing by Author "Li, Chi-Yu"

Now showing 1 - 16 of 16

A Fast Converging Mechanism for Load Balancing among SDN Multiple Controllers
(2018-01-01)
Chen, Yan-Ting
;
Li, Chi-Yu
;
Wang, Kuochen
;
資訊工程學系
;
Department of Computer Science
Load balancing among multiple controllers is a critical issue in the software-defined networking (SDN), since traffic dynamics prevent control-plane loads from being evenly distributed among controllers. Load imbalance may cause some controllers to be overloaded while the other controllers are still underutilized. Though there have been several proposed solutions, they do not consider the convergence time of load balancing. We thus propose a fast-converging load balancing (FCLB) mechanism that seeks to achieve fast convergence for balancing loads (i.e., assigning switches) among the SDN controllers. Fast convergence can rapidly release controllers from being overloaded, thereby shortly recovering network performance and preventing some unanticipated results (e.g., controller crash). Searching for the optimal solution from a large set of switch-controller combinations can lead to a large delay, which can aggravate negative impacts from overloading. We thus leverage the genetic algorithm to find a near-optimal solution. Our simulation results show that FCLB has at least 20.7% faster convergence time than the other mechanisms while achieving better load balancing performance.
A MAC protocol for multi-channel multi-interface wireless mesh network using hybrid channel assignment scheme
(2007-07-01)
Li, Chi-Yu
;
Jeng, An-Kai
;
Jan, Rong-Hong
;
資訊工程學系
;
Department of Computer Science
In recent years, Wireless Mesh Network (WMN) which uses a multi-hop configuration to extend the reach of the last-mile access to Internet has come into public notice. WMN improves network performance by the use of multiple orthogonal (non-overlapping) channels and multiple wireless interfaces. However, the Medium Access Control (MAC) protocol in IEEE 802.11 standard was designed and suited for only one channel and one interface. In this paper, we present a new MAC protocol which is specially designed for multi-channel and multi-interface WMNs. The proposed MAC protocol employs a hybrid channel assignment strategy to solve the rendezvous problem and a waiting time scheme for updating network allocation vectors (NAVs) to solve the multi-channel hidden terminal problem. Simulation results show that the proposed protocol can achieve a better utilization of both interfaces and channels.
An Integrated Edge and Fog System for Future Communication Networks
(2018-01-01)
Kuo, Ping-Heng
;
Mourad, Alain
;
Lu, Chenguang
;
Berg, Miguel
;
Duquennoy, Simon
Put together, the edge and fog form a large diverse pool of computing and networking resources from different owners that can be leveraged towards low latency applications as well as for alleviating high traffic volume in future networks including 5G and beyond. This paper sets out a framework for the integration of edge and fog computing and networking leveraging on ongoing specifications by ETSI MEC ISG and the OpenFog Consortium. It also presents the technological gaps that need to be addressed before such an integrated solution can be developed. These noticeably include challenges relating to the volatility of resources, heterogeneity of underlying technologies, virtualization of devices, and security issues. The framework presented is a Launchpad for a complete solution under development by the 5G-CORAL consortium.
An Integrated, Virtualized Joint Edge and Fog Computing System with Multi-RAT Convergence
(2018-01-01)
Rapone, Damiano
;
Quasso, Roberto
;
Chundrigar, Shahzoob Bilal
;
Talat, Samer T.
;
Cominardi, Luca
Notably, developing an innovative architectural network paradigm is essential to address the technical challenging of 5G applications' requirements in a unified platform. Forthcoming applications will provide a wide range of networking, computing and storage capabilities closer to the endusers. In this context, the 5G-PPP Phase two project named "5G-CORAL: A 5G Convergent Virtualized Radio Access Network Living at the Edge" aims at identifying and experimentally validating which are the key technology innovations allowing for the development of a convergent 5G multi-RAT access based on a virtualized Edge and Fog architecture being scalable, flexible and interoperable with other domains including transport, core network and distant Clouds. In 5G-CORAL, an architecture is proposed based on ETSI MEC and ETSI NFV frameworks in a unified platform. Then, a set of exemplary use cases benefiting from Edge and Fog networks in near proximity of the end-user are proposed for demonstration on top of connected car, shopping mall and high-speed train platforms.
Communications and Networking Technologies for Intelligent Drone Cruisers
(2019-01-01)
Wang, Li-Chun
;
Lai, Chuan-Chi
;
Shuai, Hong-Han
;
Lin, Hsin-Piao
;
Li, Chi-Yu
Future mobile communication networks require an Aerial Base Station (ABS) with fast mobility and long-term hovering capabilities. At present, unmanned aerial vehicles (UAV) or drones do not have long flight times and are mainly used for monitoring, surveillance, and image post-processing. On the other hand, the traditional airship is too large and not easy to take off and land. Therefore, we propose to develop an "Artificial Intelligence (AI) Drone-Cruiser" base station that can help 5G mobile communication systems and beyond quickly recover the network after a disaster and handle the instant communications by the flash crowd. The drone-cruiser base station can overcome the communications problem for three types of flash crowds, such as in stadiums, parades, and large plaza so that an appropriate number of aerial base stations can be accurately deployed to meet large and dynamic traffic demands. Artificial intelligence can solve these problems by analyzing the collected data, and then adjust the system parameters in the framework of Self-Organizing Network (SON) to achieve the goals of self-configuration, self-optimization, and self-healing. With the help of AI technologies, 5G networks can become more intelligent. This paper aims to provide a new type of service, On-Demand Aerial Base Station as a Service. This work needs to overcome the following live technical challenges: innovative design of drone-cruisers for the long-time hovering, crowd estimation and prediction, rapid 3D wireless channel learning and modeling, 3D placement of aerial base stations and the integration of WiFi front-haul and millimeter wave/WiGig back-haul networks.
Enabling Seamless WiGig/WiFi Handovers in Tri-band Wireless Systems
(2017-01-01)
Li, Yao-Yu
;
Li, Chi-Yu
;
Chen, Wei-Han
;
Yeh, Chia-Jui
;
Wang, Kuochen
WiGig enables wireless multi-gigabit communication over 60GHz band. However, its usage scenarios may be constrained by two major limitations: line-of-sight propagation and very short transmission range. We seek to boost the WiGig's usability by using WiFi to complement its limitations in triband (2.4/5/60GHz) wireless systems. Our goal is to let a triband client have multimedia services at the WiGig's very high speed without any hassle. When the WiGig link is down or performs bad, not only can the client temporarily handover to WiFi without service interruption, but its ongoing multimedia services can also adapt to the WiFi's slower link. Though the IEEE 802.11ad standard has proposed an FST (Fast Session Transfer) mechanism to support handover operations at the link layer, it does not satisfy our goal due to two reasons. First, it does not specify when to performWiGig/WiFi handovers. Second, it is not application-aware to achieve the service adaptation. To this end, we design and implement an application-aware, seamless WiGig/WiFi handover solution above the network layer. It ensures timely handover trigger for the WiGig's abrupt link interruption, keeps service continuity during handovers, and adapts multimedia service qualities to differentWiGig/WiFi links. Our demo confirms its viability. We show that a video streaming service at the client is not interrupted during WiGig/WiFi handovers, which are triggered by mobility or the WiGig's signal blockage, but smoothly switches between different resolutions according to different links.
Exploring the Insecurity of Google Account Registration Protocol via Model Checking
(2019-01-01)
Xie, Tian
;
Wang, Sihan
;
Tu, Guan-Hua
;
Li, Chi-Yu
;
Lei, Xinyu
People nowadays use online service accounts (e.g., Gongle, Facebook, Twitter) to access certain services. Among them, Google accounts have become increasingly important for users. Not only do many Google services (e.g., Gmail, Google Voice, Google Play, etc.) require them, but many online services also trust and rely on them for operational needs (e.g., login based on Google accounts). This trend introduces a new type of attacks that create a large number of fake, but valid, Google accounts. The fake Google accounts allow the adversary to launch various cyber attacks towards Google account-related services. It motivates us to conduct an empirical security study on the Google account registration service. In this paper, we apply model checking techniques to systematically analyze the insecurity of Google account registration service. We develop a model-checking tool, GAcctAnalyzer, which consists of two phases: (1) service screening phase, which generates counterexamples from the violation of desired properties, and (2) experimental validation phase, which validates the counterexamples through real experiments. We use GAcctAnalyzer to discover four security vulnerabilities including design defects, operational slips. etc. Based on the discovered vulnerabilities, we devise two practical attacks against mobile users and Google: fake Google account generation and Google text/voice spamming attack. They can not only threaten the security of mobile applications and online services, but also cause the Google company to receive user complaints and lawsuits. We finally confirm the feasibility of these attacks through experiments, assess the real-world impact, and propose recommended solutions.
How Voice Service Threatens Cellular-Connected IoT Devices in the Operational 4G LTE Networks
(2018-01-01)
Xie, Tian
;
Li, Chi-Yu
;
Tang, Jiliang
;
Tu, Guan-Hua
;
資訊工程學系
LTE networks are rolling out cellular Internetof-Things (IoT) services. Cellular-connected IoT devices are becoming increasingly popular and the number is forecasted to grow almost fourfold from 2015 to 2021. Since they share the same infrastructure with non-IoT devices such as smartphones, we may expect no big differences between them in terms of voice/data service accounting/charging (e.g., paying for what you get) and security risks. However, our study shows that cellular IoT users may pay more than what they get, as well as are vulnerable to voice signaling spams and thus suffer from an overcharging attack which leads to financial loss or denial of service. We validate our proof-of-concept attack in a major U.S. cellular network operator which takes higher than 35% market share. We finally propose a solution to address the identified security vulnerabilities.
New Security Threats Caused by IMS-based SMS Service in 4G LTE Networks
(2016)
Tu, Guan-Hua
;
Li, Chi-Yu
;
Peng, Chunyi
;
Li, Yuanjie
;
Lu, Songwu
SMS (Short Messaging Service) is a text messaging service for mobile users to exchange short text messages. It is also widely used to provide SMS-powered services (e.g., mobile banking). With the rapid deployment of all-IP 4G mobile networks, the underlying technology of SMS evolves from the legacy circuit-switched network to the IMS (IP Multimedia Subsystem) system over packet-switched network. In this work, we study the insecurity of the IMS-based SMS. We uncover its security vulnerabilities and exploit them to devise four SMS attacks: silent SMS abuse, SMS spoofing, SMS client DoS, and SMS spamming. We further discover that those SMS threats can propagate towards SMS-powered services, thereby leading to three malicious attacks: social network account hijacking, unauthorized donation, and unauthorized subscription. Our analysis reveals that the problems stem from the loose security regulations among mobile phones, carrier networks, and SMS-powered services. We finally propose remedies to the identified security issues.
Release-time-based multi-channel MAC protocol for wireless mesh networks
(2011-06-23)
Jeng, Andy An-Kai
;
Jan, Rong-Hong
;
Li, Chi-Yu
;
Chen, Chien
;
資訊工程學系
The wireless mesh network (WMN) has been considered one of the most promising techniques for extending broadband access to the last mile. In order to utilize multiple channels to increase the throughput in WMNs, a variety of multi-channel MAC (MMAC) protocols have been proposed in the literature. In particular, the dedicated control channel (DCC) approach can greatly simply many design issues in multi-channel environments by using a common control channel to exchange control signals. On the other hand, it allows each sender-receiver pair to dynamically select a data channel for their data transmission in an on-demand matter. However, the common control channel would become a bottleneck of the overall performance. Besides, the selection of data channels would be highly related to the final throughput. In this paper, we propose a new MMAC protocol, named the release-time-based MMAC (RTBM) to overcome the control channel bottleneck and data channel selection problems in the DCC approach. The RTBM consists of three major components: (1) Control initiation-time predication (CIP); (2) Dynamic data-flow control (DDC); (3) Enhanced channel selection (ECS). The CIP can predict a proper initiation time for each control process to reduce control overhead. The DDC can dynamically adjust the flow of each data transmission to fully exploit the channel bandwidth. The ECS can achieve a higher reusability of data channels to further enhance the throughput. Simulation results show that the RTBM can substantially improve the throughput in both single-hop and multihop networks. (C) 2011 Elsevier B.V. All rights reserved.
ReSDN: A Lightweight Solution for Data-plane State Recovery in Software-defined Networks
(2017-01-01)
Chen, Guan-Rong
;
Li, Chi-Yu
;
Wang, Kuochen
;
資訊工程學系
;
Department of Computer Science
Software-Defined Networking (SDN) benefits from the development flexibility of control-plane applications (SDN-Apps), which allows third parties to make contributions. Such flexibility may expose SDN networks to security threats, since SDN-Apps may be malicious or prone to implementation bugs. These buggy/malicious SDN-Apps may contaminate the data plane with abnormal network actions, which may not be prevented before they are committed to the data plane. This contamination may lead to network crash or poor network performance. We thus present ReSDN, a lightweight solution for data-plane state recovery, to recover an SDN data plane from a contaminated state. It requires neither switch modification nor the intervention of SDN-Apps, both of which current recovery solutions rely on. It leverages the concept of FP-tree (Frequent Pattern tree) to maintain the dependency of event transactions and network actions to achieve correct recovery. Our evaluations validate the viability of our ReSDN design, and show that it can recover more than twice as fast as the other type of recovery approach, rollback recovery.
Setting Malicious Flow Entries Against SDN Operations: Attacks and Countermeasures
(2018-01-01)
Lin, Cheng-Hsu
;
Li, Chi-Yu
;
Wang, Kuochen
;
資訊工程學系
;
Department of Computer Science
Software-defined networking (SDN) apps are developed to support various functions (e.g., traffic engineering, routing, security, etc.) for SDN networks. Their operations rely on the APIs offered by the control plane. They may be compromised or designed to be malicious by third parties. Though there have been many studies against malicious apps, they only restrict the APIs used by them with coarse-grained controls. In this work, we seek to show that some malicious flow entries cannot be detected or prevented by current defenses. They may impede the operations of control-plane services or hinder packets from being forwarded correctly in the data plane. To show their negative impact, we devise two attacks, topology spoofing and forwarding-based DoS, as well as examine their damage and analyze root causes. We then propose a context-aware, event-based anomaly detection (CEAD) framework to defend against the malicious flow entries. It provides more fine-grained controls over the flow entries set by apps. Different from other studies, it does anomaly detection by examining the context correlation between an event, the app registering it, and the flow entries set by the app for the event. Our evaluation results show that the CEAD can detect all the malicious flow entries in our given cases, and confirm its scalability with negligible overhead at increasing TCP connection attempt rates.
The Dark Side of Operational Wi-Fi Calling Services
(2018-01-01)
Xie, Tian
;
Tu, Guan-Hua
;
Li, Chi-Yu
;
Peng, Chunyi
;
Li, Jiawei
All of four major U.S. operators have rolled out nationwide Wi-Fi calling services. They are projected to surpass VoLTE (Voice over LTE) and other VoIP services in terms of mobile IP voice usage minutes in 2018. They enable mobile users to place cellular calls over Wi-Fi networks based on the 3GPP IMS (IP Multimedia Subsystem) technology. Compared with conventional cellular voice solutions, the major difference lies in that their traffic traverses untrustful Wi-Fi networks and the Internet. This exposure to insecure networks may cause the Wi-Fi calling users to suffer from security threats. Its security mechanisms are similar to the VoLTE, because both of them are supported by the IMS. They include SIM-based security, 3GPP AKA (Authentication and Key Agreement), IPSec (Internet Protocol Security), etc. However, are they sufficient to secure Wi-Fi calling services? Unfortunately, our study yields a negative answer. In this work, we explore security issues of the operational Wi-Fi calling services in three major U.S. operators' networks using commodity devices. We disclose that current Wi-Fi calling security is not bullet-proof. We uncover four vulnerabilities which stem from improper standard designs, device implementation issues and network operation slips. By exploiting them, we devise two proof-of-concept attacks: user privacy leakage and telephony harassment or denial of voice service (THDoS); they can bypass the security defenses deployed on both mobile devices and network infrastructure. We have confirmed their feasibility and simplicity using real-world experiments, as well as assessed their potential damages and proposed recommended solutions.
The Insecurity of Home Digital Voice Assistants - Vulnerabilities, Attacks and Countermeasures
(2018-01-01)
Lei, Xinyu
;
Tu, Guan-Hua
;
Liu, Alex X.
;
Li, Chi-Yu
;
Xie, Tian
Home Digital Voice Assistants (HDVAs) are getting popular in recent years. Users can control smart devices and get living assistance through those HDVAs (e.g., Amazon Alexa, Google Home) using voice. In this work, we study the insecurity of HDVA services by using Amazon Alexa and Google Home as case studies. We disclose three security vulnerabilities which root in their insecure access control. We then exploit them to devise two proof-of-concept attacks, home burglary and fake order, where the adversary can remotely command the victim's HDVA device to open a door or place an order from Amazon.com or Google Express. The insecure access control is that IIDVA devices not only rely on a single-factor authentication but also take voice commands even if no people are around them. We thus argue that HDVAs should have another authentication factor, a physical presence based access control; that is, they can accept voice commands only when any person is detected nearby. To this end, we devise a Virtual Security Button (VsButton), which leverages the WiFi technology to detect indoor human motions. Once any indoor human motion is detected, the IllY111 device is enabled to accept voice commands. Our evaluation results show that it can effectively differentiate indoor motions from the cases of no motion and outdoor motions in both laboratory and real world settings.
Transparent AAA Security Design for Low-Latency MEC-Integrated Cellular Networks
(2020-03-01)
Li, Chi-Yu
;
Lin, Ying-Dar
;
Lai, Yuan-Cheng
;
Chien, Hsu-Tung
;
Huang, Yu-Sheng
Multi-access edge computing (MEC) is a key enabler for low-latency services in the cellular network. It enables service requests to be served at the edge without reaching the Internet. However, this service model allows data traffic to bypass conventional security functions deployed at the core network, and may pose security threats. To examine its security impact, we analyze current security functions that span authentication, authorization, accounting (AAA), and access control, and then identify two major issues. First, conventional user authentication methods prevent MEC applications from achieving low-latency service offering. Second, current cellular authorization, accounting, and access control mechanisms hardly secure MEC traffic. We thus propose a transparent security design called MECsec to secure the MEC with low latency in the cellular network. It contains three main components: cellular-based OpenID Connect (OIDC) authentication, bitmap-based authorization/accounting, and two-tier hash-based access control. Especially, its transparent design does not need any changes on current cellular operations, and is standard-compliant. We implement and evaluate the MECsec prototype on an MEC-integrated LTE network architecture developed based on the OpenAirInterface (OAI) cellular platform. Our results show that the cellular-based OIDC can reduce delays of current authentication methods by up to 88.3%, and the other components can successfully defend against possible threats with negligible overhead.
V2PSense: Enabling Cellular-based V2P Collision Warning Service Through Mobile Sensing
(2018-01-01)
Li, Chi-Yu
;
Salinas, Giovanni
;
Huang, Po-Hao
;
Tu, Guan-Hua
;
Hsu, Guo-Huang
The C-V2X (Cellular Vehicle-to-Everything) technology is developing in full swing. One of its mainstream services can be the Vehicle-to-Pedestrian (V2P) service. It can protect pedestrians who are mostly vulnerable on the road. In this work, we seek to enable a V2P service that can identify which pedestrians may be nearby a dangerous driving event and then notify them of warning messages. To enable this V2P service, there are two major challenges. First, a low-latency V2P message transport is required for this infrastructure-based service. Second, the pedestrian's smartphone requires an energy-efficient outdoor positioning method instead of power-hungry GPS due to its limited battery life. We thus propose a novel solution, V2PSense, which trades off positioning precision for energy savings while achieving low-latency message transport with LTE high-priority bearers. It does a coarse-grained positioning by leveraging intermittent GPS information and mobile sensing data, which includes step count from the pedometer and cellular signal strength changes. Though the V2PSense's positioning is not as precise as the GPS, it can still ensure that all the pedestrians nearby dangerous spots can be notified. Our results show that it can achieve the average precision ratio 92.6% for estimating where the pedestrian is while saving 20.8% energy, compared with the GPS always-on case.