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Full-Text Articles in Computer Engineering

Cache-Aware Compositional Analysis Of Real-Time Multicore Virtualization Platforms, Meng Xu, Linh T.X. Phan, Oleg Sokolsky, Sisu Xi, Chenyang Lu, Christopher Gill, Insup Lee Nov 2015

Cache-Aware Compositional Analysis Of Real-Time Multicore Virtualization Platforms, Meng Xu, Linh T.X. Phan, Oleg Sokolsky, Sisu Xi, Chenyang Lu, Christopher Gill, Insup Lee

Departmental Papers (CIS)

Multicore processors are becoming ubiquitous, and it is becoming increasingly common to run multiple real-time systems on a shared multicore platform. While this trend helps to reduce cost and to increase performance, it also makes it more challenging to achieve timing guarantees and functional isolation. One approach to achieving functional isolation is to use virtualization. However, virtualization also introduces many challenges to the multicore timing analysis; for instance, the overhead due to cache misses becomes harder to predict, since it depends not only on the direct interference between tasks but also on the indirect interference between virtual processors and the ...


Migrating The Internet To Ipv6: An Exploration Of The When And Why, Mehdi Nikkhah, Roch Guerin Feb 2015

Migrating The Internet To Ipv6: An Exploration Of The When And Why, Mehdi Nikkhah, Roch Guerin

Departmental Papers (ESE)

The paper documents and to some extent elucidates the progress of IPv6 across major Internet stakeholders since its introduction in the mid 90’s. IPv6 offered an early solution to a well-understood and well-documented problem IPv4 was expected to encounter. In spite of early standardization and awareness of the issue, the Internet’s march to IPv6 has been anything but smooth, even if recent data point to an improvement. The paper documents this progression for several key Internet stakeholders using available measurement data, and identifies changes in the IPv6 ecosystem that may be in part responsible for how it has ...


Topological Conditions For In-Network Stabilization Of Dynamical Systems, Miroslav Pajic, Shreyas Sundaram, Rahul Mangharam, George Pappas Apr 2013

Topological Conditions For In-Network Stabilization Of Dynamical Systems, Miroslav Pajic, Shreyas Sundaram, Rahul Mangharam, George Pappas

Real-Time and Embedded Systems Lab (mLAB)

We study the problem of stabilizing a linear system over a wireless network using a simple in-network computation method. Specifically, we study an architecture called the "Wireless Control Network'' (WCN), where each wireless node maintains a state, and periodically updates it as a linear combination of neighboring plant outputs and node states. This architecture has previously been shown to have low computational overhead and beneficial scheduling and compositionality properties. In this paper we characterize fundamental topological conditions to allow stabilization using such a scheme. To achieve this, we exploit the fact that the WCN scheme causes the network to act ...


Analysis Of Slotted Aloha With Multipacket Messages In Clustered Surveillance Networks, Soumya Sen, David J. Dorsey, Roch A. Guérin, Mung Chiang Aug 2012

Analysis Of Slotted Aloha With Multipacket Messages In Clustered Surveillance Networks, Soumya Sen, David J. Dorsey, Roch A. Guérin, Mung Chiang

Departmental Papers (ESE)

This work presents an analysis of a cluster of finite population of low cost sensor nodes operating in a p-persistent S-Aloha framework with multipacket messages. Using this analytical framework, we consider the issue of partitioning the nodes and available frequencies into groups so as to maximize the system throughput. Assigning the nodes and frequencies into “groups” is important because the size of the group impacts the tradeoff between the benefits of frequency diversity and the cost of collision on the shared medium imposed by the nodes in a group. We study this tradeoff through analytical and numerical results and ...


Cooperative Cashing? An Economic Analysis Of Document Duplication In Cooperative Web Caching, Kartik Hosanagar, Yong Tan Jun 2012

Cooperative Cashing? An Economic Analysis Of Document Duplication In Cooperative Web Caching, Kartik Hosanagar, Yong Tan

Marketing Papers

Cooperative caching is a popular mechanism to allow an array of distributed caches to cooperate and serve each others' Web requests. Controlling duplication of documents across cooperating caches is a challenging problem faced by cache managers. In this paper, we study the economics of document duplication in strategic and nonstrategic settings. We have three primary findings. First, we find that the optimum level of duplication at a cache is nondecreasing in intercache latency, cache size, and extent of request locality. Second, in situations in which cache peering spans organizations, we find that the interaction between caches is a game of ...


Hmm-Based Characterization Of Channel Behavior For Networked Control Systems, Jian Chang, Krishna K. Venkatasubramanian, Chinwendu Enyioha, Shreyas Sundaram, George J. Pappas, Insup Lee Apr 2012

Hmm-Based Characterization Of Channel Behavior For Networked Control Systems, Jian Chang, Krishna K. Venkatasubramanian, Chinwendu Enyioha, Shreyas Sundaram, George J. Pappas, Insup Lee

Departmental Papers (CIS)

We study the problem of characterizing the behavior of lossy and data corrupting communication channels in a networked control setting, where the channel's behavior exhibits temporal correlation. We propose a behavior characterization mechanism based on a hidden Markov model (HMM). The use of a HMM in this regard presents multiple challenges including dealing with incomplete observation sequences (due to data losses and corruptions) and the lack of a priori information about the model complexity (number of states in the model). We address the first challenges by using the plant state information and history of received/applied control inputs to ...


Mind Economy: Dynamic Graph Analysis Of Communications, Alexy Khrabrov Dec 2011

Mind Economy: Dynamic Graph Analysis Of Communications, Alexy Khrabrov

Publicly Accessible Penn Dissertations

Social networks are growing in reach and impact but little is known about their structure, dynamics, or users’ behaviors. New techniques and approaches are needed to study and understand why these networks attract users’ persistent attention, and how the networks evolve. This thesis investigates questions that arise when modeling human behavior in social networks, and its main contributions are:

• an infrastructure and methodology for understanding communication on graphs;

• identification and exploration of sub-communities;

• metrics for identifying effective communicators in dynamic graphs;

• a new definition of dynamic, reciprocal social capital and its iterative computation

• a methodology to study influence in social ...


On The Economic Viability Of Network Systems And Architectures, Soumya Sen May 2011

On The Economic Viability Of Network Systems And Architectures, Soumya Sen

Publicly Accessible Penn Dissertations

Understanding the relationship between technology and economics is fundamental to making judicious policy and design decisions. Many technologies that are successful in meeting their technical goals often fail to get adopted due to economic factors. This holds true even for networked systems, e.g., the Internet, which witnessed failures in the adoption of QoS solutions, IPv6 migration etc., due to factors such as high costs, lack of demand, and weight of incumbency. To gain better insights into these issues, researchers need access to analytical frameworks that account for both technological and economic factors and provide useful design guidelines. This dissertation ...


On The Feasibility And Efficacy Of Protection Routing In Ip Networks, Kin Wah (Eric) Kwong, Lixin Gao, Roch A. Guérin, Zhi-Li Zhang Feb 2011

On The Feasibility And Efficacy Of Protection Routing In Ip Networks, Kin Wah (Eric) Kwong, Lixin Gao, Roch A. Guérin, Zhi-Li Zhang

Departmental Papers (ESE)

With network components increasingly reliable, routing is playing an ever greater role in determining network reliability. This has spurred much activity in improving routing stability and reaction to failures, and rekindled interest in centralized routing solutions, at least within a single routing domain. Centralizing decisions eliminates uncertainty and many inconsistencies, and offers added flexibility in computing routes that meet different criteria. However, it also introduces new challenges; especially in reacting to failures where centralization can increase latency. This paper leverages the flexibility afforded by centralized routing to address these challenges. Specifically, we explore when and how standby backup forwarding options ...


The Wireless Control Network: Synthesis And Robustness, Miroslav Pajic, Shreyas Sundaram, Jerome Le Ny, George J. Pappas, Rahul Mangharam Dec 2010

The Wireless Control Network: Synthesis And Robustness, Miroslav Pajic, Shreyas Sundaram, Jerome Le Ny, George J. Pappas, Rahul Mangharam

Real-Time and Embedded Systems Lab (mLAB)

We consider the problem of stabilizing a plant with a network of resource constrained wireless nodes. Traditional networked control schemes are designed with one of the nodes in the network acting as a dedicated controller, while the other nodes simply route information to and from the controller and the plant. We introduce the concept of a Wireless Control Network (WCN) where the entire network itself acts as the controller. Specifically, at each time-step, each node updates its internal state to be a linear combination of the states of the nodes in its neighborhood. We show that this causes the entire ...


The Wireless Control Network: Monitoring For Malicious Behavior, Shreyas Sundaram, Miroslav Pajic, Christoforos N. Hadjicostis, Rahul Mangharam, George J. Pappas Dec 2010

The Wireless Control Network: Monitoring For Malicious Behavior, Shreyas Sundaram, Miroslav Pajic, Christoforos N. Hadjicostis, Rahul Mangharam, George J. Pappas

Real-Time and Embedded Systems Lab (mLAB)

We consider the problem of stabilizing a plant with a network of resource constrained wireless nodes. In a companion paper, we developed a protocol where each node repeatedly transmits a linear combination of the values in its neighborhood. For certain topologies, we showed that these linear combinations can be designed so that the closed loop system is stable (i.e., the wireless network itself acts as a controller for the plant). In this paper, we design a Intrusion Detection System (IDS) for this control scheme, which observes the transmissions of certain nodes in the network and uses that information to ...


The Impact Of Reprovisioning On The Choice Of Shared Versus Dedicated Networks, Soumya Sen, Kristin Yamauchi, Roch Guerin, Kartik Hosanagar Sep 2010

The Impact Of Reprovisioning On The Choice Of Shared Versus Dedicated Networks, Soumya Sen, Kristin Yamauchi, Roch Guerin, Kartik Hosanagar

Departmental Papers (ESE)

As new network services emerge, questions about service deployment and network choices arise. Although shared networks, such as the Internet, offer many advantages, combining heterogeneous services on the same network need not be the right answer as it comes at the cost of increased complexity. Moreover, deploying new services on dedicated networks is becoming increasingly viable, thanks to virtualization technologies. In this work, we introduce an analytical framework that gives Internet Service Providers the ability to explore the trade-offs between shared and dedicated network infrastructures. The framework accounts for factors such as the presence of demand uncertainty for new services ...


Fostering Ipv6 Migration Through Network Quality Differentials, Roch A. Guérin, Kartik Hosanagar Jun 2010

Fostering Ipv6 Migration Through Network Quality Differentials, Roch A. Guérin, Kartik Hosanagar

Departmental Papers (ESE)

Although IPv6 has been the next generation Internet protocol for nearly 15 years, new evidences indicate that transitioning from IPv4 to IPv6 is about to become a more pressing issue. This paper attempts to quantify if and how such a transition may unfold. The focus is on ``connectivity quality,'' e.g., as measured by users' experience when accessing content, as a possible incentive (or disincentive) for migrating to IPv6, and on ``translation costs'' (between IPv6 and IPv4) that Internet Service Providers will incur during this transition. The paper develops a simple model that captures some of the underlying interactions, and ...


Safe Inter-Domain Routing Under Diverse Commercial Agreements, Yong Liao, Lixin Gao, Roch A. Guérin, Zhi-Li Zhang May 2010

Safe Inter-Domain Routing Under Diverse Commercial Agreements, Yong Liao, Lixin Gao, Roch A. Guérin, Zhi-Li Zhang

Departmental Papers (ESE)

Commercial agreements drive the routing policies used in today's Internet. The two most extensively studied commercial agreements are transit and peering; however, they are only two of many diverse and continuously evolving commercial agreements that ISPs enter into. So far, the only known practical safe and robust routing policy is Gao and Rexford's policy guideline, which is applicable to transit and peering agreements only. It is, therefore, of importance to identify routing policies that are safe and robust and at the same time capable of accommodating the diverse commercial agreements existing in the Internet. In particular, this paper ...


Modeling The Dynamics Of Network Technology Adoption And The Role Of Converters, Soumya Sen, Youngmi Jin, Roch A. Guérin, Kartik Hosanagar Apr 2010

Modeling The Dynamics Of Network Technology Adoption And The Role Of Converters, Soumya Sen, Youngmi Jin, Roch A. Guérin, Kartik Hosanagar

Departmental Papers (ESE)

New network technologies constantly seek to displace incumbents. Their success depends on technological superiority, the size of the incumbent’s installed base, users’ adoption behaviors, and various other factors. The goal of this paper is to develop an understanding of competition between network technologies, and identify the extent to which different factors, in particular converters (a.k.a. gateways), affect the outcome. Converters can help entrants overcome the influence of the incumbent’s installed base by enabling cross-technology interoperability. However, they have development, deployment, and operations costs, and can introduce performance degradations and functionality limitations, so that if, when, why ...


Interactions, Competition And Innovation In A Service-Oriented Internet: An Economic Model, Zhi-Li Zhang, Papak Nabipay, Andrew Odlyzko, Roch A. Guérin Dec 2009

Interactions, Competition And Innovation In A Service-Oriented Internet: An Economic Model, Zhi-Li Zhang, Papak Nabipay, Andrew Odlyzko, Roch A. Guérin

Departmental Papers (ESE)

This paper presents a new economic approach for studying competition and innovation in a complex and highly interactive system of network providers, users, and suppliers of digital goods and services (i.e., service providers). It employs Cournot and Bertrand games to model competition among service providers and network providers, respectively, and develops a novel unified model to capture the interaction and competition among these players in a “service-oriented” Internet. Incentives for service and network innovation are studied in this model.


On The Feasibility And Efficacy Of Protection Routing In Ip Networks, Kin-Wah (Eric) Kwong, Lixin Gao, Roch A. Guérin, Zhi-Li Zhang Dec 2009

On The Feasibility And Efficacy Of Protection Routing In Ip Networks, Kin-Wah (Eric) Kwong, Lixin Gao, Roch A. Guérin, Zhi-Li Zhang

Departmental Papers (ESE)

With network components increasingly reliable, routing is playing an ever greater role in determining network reliability. This has spurred much activity in improving routing stability and reaction to failures, and rekindled interest in centralized routing solutions, at least within a single routing domain. Centralizing decisions eliminates uncertainty and many inconsistencies, and offers added flexibility in computing routes that meet different criteria. However, it also introduces new challenges; especially in reacting to failures where centralization can increase latency. This paper leverages the flexibility afforded by centralized routing to address these challenges. Specifically, we explore when and how standby backup forwarding options ...


Online Optimization Of 802.11 Mesh Networks, Theodoros Salonidis, Georgios Sotiropoulos, Roch A. Guérin, Ramesh Govindan Oct 2009

Online Optimization Of 802.11 Mesh Networks, Theodoros Salonidis, Georgios Sotiropoulos, Roch A. Guérin, Ramesh Govindan

Departmental Papers (ESE)

802.11 wireless mesh networks are ubiquitous, but suffer from severe performance degradations due to poor synergy between the 802.11 CSMA MAC protocol and higher layers. Several solutions have been proposed that either involve significant modifications to the 802.11 MAC or legacy higher layer protocols, or rely on 802.11 MAC models seeded with off-line measurements performed during network downtime.

We introduce a technique for online optimization of 802.11 wireless mesh networks using rate control at the network layer. The technique is based on a lightweight model that characterizes the feasible rates region of an operational 802 ...


Always Acyclic Distributed Path Computation, Saikat Ray, Roch A. Guérin, Kin Wah (Eric) Kwong, Rute Sofia Oct 2009

Always Acyclic Distributed Path Computation, Saikat Ray, Roch A. Guérin, Kin Wah (Eric) Kwong, Rute Sofia

Departmental Papers (ESE)

Distributed routing algorithms may give rise to transient loops during path recomputation, which can pose significant stability problems in high-speed networks. We present a new algorithm, Distributed Path Computation with Intermediate Variables (DIV), which can be combined with any distributed routing algorithm to guarantee that the directed graph induced by the routing decisions remains acyclic at all times. The key contribution of DIV, besides its ability to operate with any routing algorithm, is an update mechanism using simple message exchanges between neighboring nodes that guarantees loop-freedom at all times. DIV provably outperforms existing loop-prevention algorithms in several key metrics such ...


Modeling The Dynamics Of Network Technology Adoption And The Role Of Converters, Soumya Sen, Youngmi Jin, Roch Guérin, Kartik Hosanagar Jun 2009

Modeling The Dynamics Of Network Technology Adoption And The Role Of Converters, Soumya Sen, Youngmi Jin, Roch Guérin, Kartik Hosanagar

Departmental Papers (ESE)

New network technologies constantly seek to displace incumbents. Their success depends on technological superiority, the size of the incumbent's installed base, users' adoption behaviors, and various other factors. The goal of this paper is to develop an understanding of competition between network technologies, and identify the extent to which different factors, in particular converters (a.k.a. gateways), affect the outcome. Converters can help entrants overcome the influence of the incumbent's installed base by enabling cross-technology inter-operability. However, they have development, deployment, and operations costs, and can introduce performance degradations and functionality limitations, so that if, when, why ...


Broadband Adoption And Content Consumption, Lorin M. Hitt, Prasanna B Tambe Oct 2007

Broadband Adoption And Content Consumption, Lorin M. Hitt, Prasanna B Tambe

Operations, Information and Decisions Papers

We explore how broadband access drives changes in the quantity and diversity of consumption of online content by using panel data that describes household Internet usage before and after broadband adoption. Our data suggests that on average, broadband adoption increases usage by over 1300 min per month. We also find that information consumption becomes more evenly distributed within the population, driven in part by post-adoption usage gains of almost 1800 min per month among individuals who were in the lowest usage quintile before adopting broadband. After adopting broadband, this pre-adoption lowest-usage quintile consumes content in greater quantities than users in ...


Public Health For The Internet Φ Towards A New Grand Challenge For Information Management, Joseph M. Hellerstein, Tyson Condie, Minos Garofalakis, Boon Thau Loo, Petros Maniatis, Timothy Roscoe, Nina A. Taft Jan 2007

Public Health For The Internet Φ Towards A New Grand Challenge For Information Management, Joseph M. Hellerstein, Tyson Condie, Minos Garofalakis, Boon Thau Loo, Petros Maniatis, Timothy Roscoe, Nina A. Taft

Departmental Papers (CIS)

Business incentives have brought us within a small factor of achieving the database community's Grand Challenge set out in the Asilomar Report of 1998. This paper makes the case for a new, focused Grand Challenge: Public Health for the Internet. The goal of PHI (or φ) is to enable collectives of hosts on the Internet to jointly monitor and promote network health by sharing information on network conditions in a peer-to-peer fashion. We argue that this will be a positive effort for the research community for a variety of reasons, both in terms of its technical reach and its ...


Information Technology And Firm Boundaries: Evidence From Panel Data, Lorin. M. Hitt Jun 1999

Information Technology And Firm Boundaries: Evidence From Panel Data, Lorin. M. Hitt

Operations, Information and Decisions Papers

Previous literature has suggested that information technology (IT) can affect firm bound- aries by changing the costs of coordinating economic activity within and between firms (internal and external coordination). This paper examines the empirical relationship between IT and firm structure and evaluates whether this structure is consistent with prior arguments about IT and coordination. We formulate an empirical model to relate the use of information technology capital to vertical integration and diversification. This model is tested using an 8- year panel data set of information technology capital stock, firm structure, and relevant control variables for 549 large firms.

Overall, increased ...


Equivalent Capacity And Its Application To Bandwidth Allocation In High-Speed Networks, Roch A. Guérin, Hamid Ahmadi, Mahmoud Naghshineh Sep 1991

Equivalent Capacity And Its Application To Bandwidth Allocation In High-Speed Networks, Roch A. Guérin, Hamid Ahmadi, Mahmoud Naghshineh

Departmental Papers (ESE)

High-speed fast-packet-switched network architectures are capable of supporting a wide range of connections with different bandwidth requirements and traffic characteristics. While this environment provides increased flexibility in supporting various services, its dynamic nature poses difficult traffic control problems when trying to achieve efficient use of network resources. One such a problem is the issue of bandwidth management and allocation. Because of the statistical multiplexing of all connections at the physical layer and the variations of connections bit rate, it is important to characterize, for a given Grade-Of-Service (GOS), both the effective bandwidth requirement of a single connection and the aggregate ...