Computer Science

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The Computer Science Department at Montana State University supports the Mission of the College of Engineering and the University through its teaching, research, and service activities. The Department educates undergraduate and graduate students in the principles and practices of computer science, preparing them for computing careers and for a lifetime of learning.

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ParaNets: A parallel network architecture for challenged networks
(IEEE, 2007-03) Harras, Khaled A.; Wittie, Mike P.; Almeroth, Kevin C.; Belding, Elizabeth M.
Networks characterized by challenges, such as intermittent connectivity, network heterogeneity, and large delays, are called “challenged networks”. We propose a novel network architecture for challenged networks dubbed Parallel Networks, or, ParaNets. The vision behind ParaNets is to have challenged network protocols operate over multiple heterogenous networks, simultaneously available, through one or more devices. We present the ParaNets architecture and discuss its short-term challenges and long-term implications. We also argue, based on current research trends and the ParaNets architecture, for the evolution of the conventional protocol stack to a more flexible cross-layered protocol tree. To demonstrate the potential impact of ParaNets, we use Delay Tolerant Mobile Networks (DTMNs) as a representative challenged network over which we evaluate ParaNets. Our ultimate goal in this paper is to open the way for further work in challenged networks using ParaNets as the underlying architecture.
MIST: Cellular data network measurement for mobile applications
(Conference on Broadband Communications, Networks and Systems (BROADNETS), 2007-09) Wittie, Mike P.; Stone-Gross, Brett; Almeroth, Kevin C.; Belding, Elizabeth M.
The rapid growth in the popularity of cellular networks has led to aggressive deployment and a rapid expansion of mobile services. Services based on the integration of cellular networks into the Internet have only recently become available, but are expected to become very popular. One current limitation to the deployment of many of these services is poor or unknown network performance, particularly in the cellular portion of the network. Our goal in this paper is to motivate and present the Mobile Internet Services Test (MIST) platform, a new distributed architecture to measure and characterize cellular network performance as experienced by mobile devices. We have used MIST to conduct preliminary measurements; evaluate MIST’s effectiveness; and motivate further measurement research.
Mobile ad hoc networks (MANET) protocols evaluation framework
(IEEE, 2007-10) Slavin, Vadim A.; Polyakov, Michael; Quilling, Mark; Wittie, Mike P.; Andrews, Matthew
We propose a novel, robust MANET protocols evaluation framework which enables researchers to track performance metrics and evaluate theoretical predictions. This framework speeds up the research and development spirals, provides faster feedback to algorithm developers and closes the loop between theory and qualitative analysis of the protocols' performance. Our test and evaluation effort is divided into two parts. Rapid prototyping and evaluation of proposed algorithms is performed in the MATLAB environment. These tools enable us to numerically analyze performance, capabilities, convergence, and robustness of new algorithms. The second higher fidelity approach is the test and evaluation framework developed in OPNET simulation environment. Its unique features are the novel application and evaluation process including sophisticated statistics collection and an event logging architecture.
Exploiting Parallel Networks Using Dynamic Channel Scheduling
(Wireless Internet Conference (WICON), 2008-11) Deek, Lara B.; Almeroth, Kevin C.; Wittie, Mike P.; Harras, Khaled A.
Many researchers have been focusing on the outcomes and consequences of the rapid increase and proliferation of mobile wireless technologies. If it is not already the case, it will soon be rare for a user to be in a situation where absolutely no network connection exists. In fact, through numerous devices, users will soon expect to be connected in all places at all times. Through the great variety and increase in the capabilities of these devices, it is not a surprise to find a single user with many connection opportunities. As a result, we believe that the next major evolution of wireless mobile networks will be in the exploitation of multiple network connections in parallel. Due to network heterogeneity, the major challenge in such situations is to determine the way that these networks can be utilized to better serve different network applications. In this work, we propose a dynamic channel scheduling mechanism that adapts to the state of the available channels to provide more efficient usage of network connectivity. We do so by observing channel throughput, creating a set of channel usage combinations, and then choosing the most efficient combination. We evaluate an implementation of the proposed mechanism using emulation. Our results show that under realistic conditions our dynamic approach greatly improves cost delay metrics, and the overall user-perceived performance compared to a more static approach.
On The Implications of Routing Metric Staleness in Delay Tolerant Networks
(Elsevier, 2009) Wittie, Mike P.; Harras, Khaled A.; Almeroth, Kevin C.; Belding, Elizabeth M.
Delay Tolerant Network (DTN) routing addresses challenges of providing end-to-end service where end-to-end data forwarding paths may not exist. The performance of current DTN routing protocols is often limited by routing metric ‘‘staleness”, i.e., routing information that becomes out-of-date or inaccurate because of long propagation delays. Our previous work, ParaNets, proposed a new opportunistic network architecture in which the data channel is augmented by a thin end-to-end control channel. The control channel is adequate for the exchange of control traffic, but not data. In this paper we present Cloud Routing, a routing solution for the ParaNets architecture. We motivate the need for such a solution, not only because of stale routing metrics, but also because of congestion that can occur in DTNs. Unable to use up-to-date routing metrics to limit congestion, existing DTN routing solutions suffer from low goodput and long data delivery delays. We show how Cloud Routing avoids congestion by smart use of forwarding opportunities based on up-to-date routing metrics. We evaluate our solution using extensive OPNET simulations. Cloud Routing extends network performance past what is currently possible and motivates a new class of globally cognizant DTN routing solutions.
Internet Service in Developing Regions Through Network Coding
(IEEE, 2009) Wittie, Mike P.; Almeroth, Kevin C.; Belding, Elizabeth M.; Rimac, Ivica; Hilt, Volker
The availability of Internet services brings many benefits to developing regions, yet Internet deployment levels in these regions remain staggeringly low. In this work we investigate how existing cellular deployments, which have enjoyed more rapid and wider deployment than client Internet infrastructure, could be used to provide very low cost Internet services in underdeveloped rural areas. We propose a new service model in which traffic is delivered over multihop client-to-client connections that are coordinated by end-to-end control traffic exchanged over cellular infrastructure. To enable this scheme in low client density rural settings, we propose a novel data forwarding mechanism for opportunistic space-time paths. To explore multiple opportunistic paths, but without the high forwarding cost of replicating data on these paths, we use network coding and send only a fraction of the data on each path. Through extensive OPNET simulations we show that globally coordinated opportunistic forwarding enables service acceptable to most applications at only a fraction of cellular infrastructure load. We argue that the reduced load on the cellular infrastructure allows additional users to share services and cost of the network and has the potential to lower the per user price of data services in developing regions.
AirLab: Distributed Infrastructure for Wireless Measurements
(USENIX, 2010) Kone, Vinod; Zheleva, Mariya; Wittie, Mike P.; Zhang, Zengbin; Zhao, Xiaohan; Zhao, Ben Y.; Belding, Elizabeth M.; Zheng, Haitao; Almeroth, Kevin C.
The importance of experimental research in the field of wireless networks is well understood. So far researchers have either built their own testbeds or accessed third-party controlled testbeds (http://orbit-lab.org) or used publicly available traces (http://crawdad.cs.dartmouth.edu) for evaluation. While immensely useful, all these approaches have their drawbacks. While building own test beds requires cost and effort, third-party controlled test beds do not replicate real network deployments. On the other hand, the publicly available traces are often collected using different software and hardware platforms, making it very difficult to compare results across traces. As a result, observations are often inconsistent across different networks, leading researchers to draw potentially conflicting conclusions across their own studies. To facilitate meaningful analysis of wireless networks and protocols, we need a way to collect measurement traces across a wide variety of network deployments, all using a consistent set of measurement metrics. Widespread multi-faceted data collection will provide multiple viewpoints of the same network, enabling deeper understanding of both self and exterior interference properties, spectrum usage, network usage, and a wide variety of other factors. Furthermore, data collected in this manner across a variety of heterogeneous network types, such as university, corporate, and home environments, will facilitate cross-comparison of observed network phenomena within each of these settings. To address the critical need for comparable and consistent wireless traces, we propose AirLab, a publicly accessible distributed infrastructure for wireless measurements
Exploiting Locality of Interest in Online Social Networks
(ACM CoNEXT, 2010) Wittie, Mike P.; Pejovic, Veljko; Deek, Lara B.; Almeroth, Kevin C.; Zhao, Ben Y.
Online Social Networks (OSN) are fun, popular, and socially significant. An integral part of their success is the immense size of their global user base. To provide a consistent service to all users, Facebook, the world’s largest OSN, is heavily dependent on centralized U.S. data centers, which renders service outside of the U.S. sluggish and wasteful of Internet bandwidth. In this paper, we investigate the detailed causes of these two problems and identify mitigation opportunities. Because details of Facebook’s service remain proprietary, we treat the OSN as a black box and reverse engineer its operation from publicly available traces. We find that contrary to current wisdom, OSN state is amenable to partitioning and that its fine grained distribution and processing can significantly improve performance without loss in service consistency. Through simulations of reconstructed Facebook traffic over measured Internet paths, we show that user requests can be processed 79% faster and use 91% less bandwidth. We conclude that the partitioning of OSN state is an attractive scaling strategy for Facebook and other OSN services.
ACAR: Adaptive Connectivity Aware Routing for Vehicular Ad Hoc Networks in City Scenarios
(Springer, 2010-02) Yang, Qing; Lim, Alvin; Li, Shuang; Fang, Jian; Agrawal, Prathima
Multi-hop vehicle-to-vehicle communication is useful for supporting many vehicular applications that provide drivers with safety and convenience. Developing multi-hop communication in vehicular ad hoc networks (VANET) is a challenging problem due to the rapidly changing topology and frequent network disconnections, which cause failure or inefficiency in traditional ad hoc routing protocols. We propose an adaptive connectivity aware routing (ACAR) protocol that addresses these problems by adaptively selecting an optimal route with the best network transmission quality based on statistical and real-time density data that are gathered through an on-the-fly density collection process. The protocol consists of two parts: 1) select an optimal route, consisting of road segments, with the best estimated transmission quality, and 2) in each road segment of the chosen route, select the most efficient multi-hop path that will improve the delivery ratio and throughput. The optimal route is selected using our transmission quality model that takes into account vehicle densities and traffic light periods to estimate the probability of network connectivity and data delivery ratio for transmitting packets. Our simulation results show that the proposed ACAR protocol outperforms existing VANET routing protocols in terms of data delivery ratio, throughput and data packet delay. Since the proposed model is not constrained by network densities, the ACAR protocol is suitable for both daytime and nighttime city VANET scenarios.
Network Optimization with Dynamic Demands and Link Prices
(Allerton Conference, 2012) Patterson, Stacy; Wittie, Mike P.; Almeroth, Kevin C.; Bamieh, Bassam
We present Overlapping Cluster Decomposition (OCD), a novel distributed algorithm for network optimization targeted for networks with dynamic demands and link prices. OCD uses a dual decomposition of the global problem into local optimization problems in each node’s neighborhood. The local solutions are then reconciled to find the global optimal solution. While OCD is a descent method and thus may converge slowly in a static network, we show that OCD can more rapidly adapt to changing network conditions than previously proposed first-order and Newton-like network optimization algorithms. Therefore, OCD yields better solutions over time than previously proposed methods at a comparable communication cost.
ES-MPICH2: A Message Passing Interface with Enhanced Security
(IEEE, 2012-01) Ruan, Xiaojun; Yang, Qing; Alghamdi, Mohammed I.; Yin, Shu; Qin, Xiao
An increasing number of commodity clusters are connected to each other by public networks, which have become a potential threat to security sensitive parallel applications running on the clusters. To address this security issue, we developed a Message Passing Interface (MPI) implementation to preserve confidentiality of messages communicated among nodes of clusters in an unsecured network. We focus on M PI rather than other protocols, because M PI is one of the most popular communication protocols for parallel computing on clusters. Our MPI implementation-called ES-MPICH2-was built based on MPICH2 developed by the Argonne National Laboratory. Like MPICH2, ES-MPICH2 aims at supporting a large variety of computation and communication platforms like commodity clusters and high-speed networks. We integrated encryption and decryption algorithms into the MPICH2 library with the standard MPI interface and; thus, data confidentiality of MPI applications can be readily preserved without a need to change the source codes of the MPI applications. MPI-application programmers can fully configure any confidentiality services in MPICHI2, because a secured configuration file in ES-MPICH2 offers the programmers flexibility in choosing any cryptographic schemes and keys seamlessly incorporated in ES-MPICH2. We used the Sandia Micro Benchmark and Intel MPI Benchmark suites to evaluate and compare the performance of ES-MPICH2 with the original MPICH2 version. Our experiments show that overhead incurred by the confidentiality services in ES-MPICH2 is marginal for small messages. The security overhead in ES-MPICH2 becomes more pronounced with larger messages. Our results also show that security overhead can be significantly reduced in ES-MPICH2 by high-performance clusters. The executable binaries and source code of the ES-MPICH2 implementation are freely available at http:// www.eng.auburn.edu/~xqin/software/es-mpich2/.
MITATE: Mobile Internet Testbed for Application Traffic Experimentation
(Conference on Mobile and Ubiquitous Systems: Computing, Networking and Services (Mobiquitous), 2013) Goel, Utkarsh; Miyyapuram, Ajay; Yang, Qing; Wittie, Mike P.
This paper introduces a Mobile Internet Testbed for Application Trac Experimentation (MITATE). MITATE is the first programmable testbed to support the prototyping of application communications between mobiles and cloud datacenters. We describe novel solutions to device security and resource sharing behind MITATE. Finally, we show how MITATE can answer network performance questions crucial to mobile application design.
Cascading Impact of Lag on User Experience in Multiplayer Games
(USENIX, 2013) Howard, Eben; Cooper, Clint; Wittie, Mike P.; Yang, Qing
Playing cooperative multiplayer games should be fun for everyone involved and part of having fun in games is being able to perform well, be immersed, and stay engaged [13, 17]. These indicators of enjoyment are part of a user's Quality of Experience (QoE), a measure which further includes additional metrics such as attention levels and ability to succeed. Players stop playing the game when it ceases to provide a high enough QoE, especially in cooperative and social games. [8, 18, 19]. Industry application development and current research both operate with the assumption that for any given individual in a group, that individual's QoE is affected only by their own network condition and not the network conditions of the other group members [4, 7, 8]. We show that this assumption is incorrect. Our research shows that the QoE of all group members is negatively affected by a single member's lag (communication delay, or loss caused by poor network conditions). Understanding a user's QoE as a function that includes other users' network conditions has the potential to improve lag mitigation strategies for multiplayer games and other group applications.
IP2DC: Making Sense of Replica Selection Tools
(USENIX, 2013) Bharata, Anish; Wittie, Mike P.; Yang, Qing
Cloud-based applications being developed for consumer electronics market (tablets, smart TVs) struggle to deliver the same level of responsiveness as standalone software, leading to user frustration and slow adoption. Often the network that separates user end-hosts from server back-end is to blame. To limit the impact of poor network performance on message delay, or lag, back-end logic and application data are deployed across geographically distributed servers and user requests are directed to the closest one [14]. Such nearby servers deliver content more quickly thanks to a faster expansion of TCP congestion window and more rapid retransmissions over low round-trip time (RTT) paths. Our early results, presented in this poster, show a high level of discrepancy between the available tools and motivate further measurement as well as the need to develop techniques for more accurate server replica selection.
Jamming and Anti-jamming Techniques in Wireless Networks: A Survey
(Inderscience Publishers, Geneva, SWITZERLAND, 2014) Grover, Kanika; Lim, Alvin; Yang, Qing
Because of the proliferation of wireless technologies, jamming in wireless networks has become a major research problem due to the ease in blocking communication in wireless networks. Jamming attacks are a subset of denial of service (DoS) attacks in which malicious nodes block legitimate communication by causing intentional interference in networks. To better understand this problem, we need to discuss and analyze, in detail, various techniques for jamming and anti-jamming in wireless networks. There are two main aspects of jamming techniques in wireless ad hoc networks: types of jammers and placement of jammers for effective jamming. To address jamming problem, various jamming localization, detection and countermeasure mechanisms are studied. Finally, we describe the open issues in this field, such as energy efficient detection scheme and jammer classification.
An empirical study of reliable networking for vehicular networks using IEEE 802.11n
(Inderscience Publishers, Geneva, SWITZERLAND, 2014) Lee, Seungbae; Lim, Alvin; Yang, Qing
The IEEE 802.11n technology is becoming more and more prevalent in wireless networks due to its significant enhancements in network performance. To examine whether the reliability of 802.11n is sufficient for vehicular networks, we conducted extensive experiments on inter-vehicle and intra-vehicle communications in vehicular environments. From this empirical study, we found that 802.11n provides high performance with stable throughput and reliable coverage in most cases. However, 802.11n protocols do not detect frequent changes of propagation and polarisation due to vehicle mobility and its rate adaptation algorithms improperly select multi-stream rates under channel fading conditions, although single-stream rates perform better. Moreover, an optimal antenna alignment that enables High Throughput (HT) operation using parallel data streams needs further investigation in vehicular environments. Our findings have profound implications on the protocol design and appropriate configuration for reliable networking in vehicular networks using 802.11n.
Comparative Investigation on CSMA/CA-Based Opportunistic Random Access for Internet of Things
(IEEE, 2014-01) Tang, Chong; Song, Lixing; Balasubramani, Jagadeesh; Wu, Shaoen; Biaz, Saad; Yang, Qing; Wang, Honggang
Wireless communication is indispensable to Internet of Things (IoT). Carrier sensing multiple access/collision avoidance (CSMA/CA) is a well-proven wireless random access protocol and allows each node of equal probability in accessing wireless channel, which incurs equal throughput in long term regardless of the channel conditions. To exploit node diversity that refers to the difference of channel condition among nodes, this paper proposes two opportunistic random access mechanisms: overlapped contention and segmented contention, to favor the node of the best channel condition. In the overlapped contention, the contention windows of all nodes share the same ground of zero, but have different upper bounds upon channel condition. In the segmented contention, the contention window upper bound of a better channel condition is smaller than the lower bound of a worse channel condition; namely, their contention windows are segmented without any overlapping. These algorithms are also polished to provide temporal fairness and avoid starving the nodes of poor channel conditions. The proposed mechanisms are analyzed, implemented, and evaluated on a Linux-based testbed and in the NS3 simulator. Extensive comparative experiments show that both opportunistic solutions can significantly improve the network performance in throughput, delay, and jitter over the current CSMA/CA protocol. In particular, the overlapped contention scheme can offer 73.3% and 37.5% throughput improvements in the infrastructure-based and ad hoc networks, respectively.
Location-preserved contention-based routing in vehicular ad hoc networks
(Wiley, 2014-04) Qing, Yang; Lim, Alvin; Ruan, Xiaojun; Qin, Xiao; Kim, Dongjin
Location privacy protection in vehicular ad hoc networks considers preserving two types of information: the locations and identifications of users. However, existing solutions, which either replace identifications by pseudonyms or hide locations in areas, cannot be directly applied to geographic routing protocols because they degrade network performance. To address this issue, we proposed a location-preserved contention (LPC) based routing protocol, in which greedy forwarding is achieved using dummy distance to the destination information instead of users’ true locations. Unlike the contention-based forwarding protocol, the number of duplicated responses in LPC can be reduced by adjusting the parameter α, which is a timer scaling factor. To quantify the efficiency of location privacy protection, an entropy-based analytical method is proposed. LPC is compared with existing routing and location privacy protection protocols in simulations. Results show that LPC provides 11.7% better network performance and a higher level of location privacy protection than the second best protocol.
A Load Profile Management Integrated Power Dispatch Using a Newton-Like Particle Swarm Optimization Method
(2014-10) Wang, Caisheng; Miller, Carol J.; Nehrir, M. Hashem; Sheppard, John W.; McElmurry, Shawn P.
Load profile management (LPM) is an effective demand side management (DSM) tool for power system operation and management. This paper introduces an LPM integrated electric power dispatch algorithm to minimize the overall production cost over a given period under study by considering both fuel cost and emission factors. A Newton-like particle swarm optimization (PSO) algorithm has been developed to implement the LPM integrated optimal power dispatch. The proposed Newton-like method is embedded into the PSO algorithm to help handle equality constraints while penalty/fitness functions are used to deal with inequality constraints. In addition to illustrative example applications of the proposed Newton-like PSO technique, the optimization method has been used to realize the LPM integrated optimal power dispatch for the IEEE RTS 96 system. Simulation studies have been carried out for different scenarios with different levels of load management. The simulation results show that the LPM can help reduce generation costs and emissions. The results also verify the effectiveness of the proposed Newton-like PSO method.
A generalized optimization model of microbially driven aquatic biogeochemistry based on thermodynamic, kinetic, and stoichiometric ecological theory
(2014-12) Payn, Robert A.; Helton, A. M.; Poole, Geoffrey C.; Izurieta, Clemente Ignacio; Burgin, A. J.; Bernhardt, E. S.
We have developed a mechanistic model of aquatic microbial metabolism and growth, where we apply fundamental ecological theory to simulate the simultaneous influence of multiple potential metabolic reactions on system biogeochemistry. Software design was based on an anticipated cycle of adaptive hypothesis testing, requiring that the model implementation be highly modular, quickly extensible, and easily coupled with hydrologic models in a shared state space. Model testing scenarios were designed to assess the potential for competition over dissolved organic carbon, oxygen, and inorganic nitrogen in simulated batch reactors. Test results demonstrated that the model appropriately weights metabolic processes according to the amount of chemical energy available in the associated biochemical reactions, and results also demonstrated how simulated carbon, nitrogen, and sulfur dynamics were influenced by simultaneous microbial competition for multiple resources. This effort contributes an approach to generalized modeling of microbial metabolism that will be useful for a theoretically and mechanistically principled approach to biogeochemical analysis.