Umar Kalim

A trust model for ubiquitous systems based on vectors of trust values

Ubiquitous computing foresees a massively networked world supporting a population of diverse but cooperating mobile devices where trust relationships between entities are uncertain. Though there have been lots of effort focusing on trust for ubiquitous systems, they did not attach enough importance to uncertainty in their model. On the other hand, most of the works draw a general picture without a detailed computational model. In this paper, we present a trust model based on the vectors of trust values of different entities. The evaluation of trust depends upon the recommendation of peer entities common to the interacting entities. These recommendations are weighted according to the number and time of past interactions. Furthermore we present a method of handling false recommendations without introducing significant computational burden. The model can calculate trust between two entities in situations both in which there is past experience among the interacting entities and in which the two entities are communicating for the first time. Several tuning parameters are suggested which can be adjusted to meet the security requirement of a ubiquitous system.

Mobile-to-Grid middleware: bridging the gap between mobile and grid environments

Currently, access to Grid services is limited to resourceful devices such as desktop PCs but most mobile devices (with wireless network connections) cannot access the Grid network directly because of their resource limitations. Yet, extending the potential of the Grid to a wider audience promises increase in flexible usage and productivity. In this paper we present a middleware architecture that addresses the issues of job delegation to a Grid service, support for offline processing, secure communication, interaction with heterogeneous mobile devices and presentation of results formatted in accordance with the device specification. This is achieved by outsourcing the resource intensive tasks from the mobile device to the middleware. We also demonstrate through formal modeling using Petri nets that the addition of such a middleware causes minimum overhead and the benefits obtained outweigh this overhead.

AutoMAGI - an Autonomic middleware for enabling Mobile Access to Grid Infrastructure

Access to Grid services is currently limited to devices having substantial computing, network and memory resources such as PCs. On the other hand, most of mobile devices do not have enough capabilities to be either direct clients or services in the Grid environment. The existing middleware platforms like Globus do not fully address mobility, yet extending the potential of the Grid to a wider audience promises increase in its flexibility and productivity. Furthermore, the promising approach of autonomic computing holds the key to the self-management of such a multifarious undertaking and provides a way to further build upon this complexity without incurring additional drawbacks. In this paper we present AutoMAGI, an autonomic middleware that can handle the complexity of extending the potential of the Grid to a wider mobile audience, by incorporating the features of context-awareness, self-configuration, self-optimization, self-healing and self-protection in it. We address the issues of job delegation to a Grid service, support for offline processing, secure communication, interaction with heterogeneous mobile devices and presentation of results formatted in accordance with the device limitations

Seamless Migration of Virtual Machines across Networks

Current technologies that support live migration require that the virtual machine (VM) retain its IP network address. As a consequence, VM migration is oftentimes restricted to movement within an IP subnet or entails interrupted network connectivity to allow the VM to migrate. Thus, migrating VMs beyond subnets becomes a significant challenge for the purposes of load balancing, moving computation close to data sources, or connectivity recovery during natural disasters. Conventional approaches use tunneling, routing, and layer-2 expansion methods to extend the network to geographically disparate locations, thereby transforming the problem of migration between subnets to migration within a subnet. These approaches, however, increase complexity and involve considerable human involvement. The contribution of our paper is to address the aforementioned shortcomings by enabling VM migration across subnets and doing so with uninterrupted network connectivity. We make the case that decoupling IP addresses from the notion of transport endpoints is the key to solving a host of problems, including seamless VM migration and mobility. We demonstrate that VMs can be migrated seamlessly between different subnets - without losing network state - by presenting a backward-compatible prototype implementation and a case study.

A component-based architecture for an autonomic middleware enabling mobile access to grid infrastructure

The increasing pervasiveness of wide-area distributed computing resources, like computational Grids, has given rise to applications that have inherent problems of complexity, adaptability, dynamism and heterogeneity etc. The emerging concept of autonomic computing holds the key to the self-management of such a multifarious undertaking and provides a way to further build upon this complexity without incurring additional drawbacks. Furthermore, access to Grid services at present is generally limited to devices having substantial computing, network and memory resources whereas most of mobile devices do not have the sufficient capabilities to be either direct clients or services in the Grid environment. The existing middleware platforms like Globus do not fully address mobility, yet extending the potential of the Grid to a wider audience promises increase in its flexibility and productivity. In this paper, we present a component-based autonomic middleware that can handle the complexity of extending the potential of the Grid to a wider mobile audience, by incorporating the features of context-awareness and self-management. We also address the middleware issues of job delegation to a Grid service, support for disconnected operation/offline processing and secure communication.

Mobile-to-grid middleware: an approach for breaching the divide between mobile and grid environments

In this paper we present an architecture of a middleware layer that enables users of mobile devices to seamlessly and securely access distributed resources in a Grid. It lays the ground work for an application toolkit that addresses issues such as delegation of the job to the Grid service, interaction with heterogeneous mobile devices, support for offline processing, secure communication between the client and the middleware and presentation of results formatted in accordance with the device specification by outsourcing computationally intensive tasks with high storage and network bandwidth demands.

Decision theoretic approach to detect anomalies beyond enterprise boundaries

Many algorithms have been proposed in the last decade to detect traffic anomalies in enterprise networks. However, most of these algorithms cannot detect anomalies that occur beyond enterprise boundaries. Anomaly monitoring and detection on end-to-end Internet paths, although important for network operations, is challenging due to lack of access and control over intermediate network devices. In this paper, we propose an algorithm that detects anomalies or significant events on an end-to-end Internet path by monitoring the paths available bandwidth. We first evaluate existing algorithms on a comprehensive dataset of more than a million bandwidth measurements spanning three years. We show that existing algorithms do not incorporate the typical behavior of a path in the anomaly detection process and consequently incur accuracy degradations. We therefore propose to filter noisy bandwidth measurements to extract a typical or baseline statistical distribution of a paths bandwidth. This baseline model is in turn leveraged in a generic decision-theoretic framework to provide timely detection of significant path events. We show that the proposed detector provides highly accurate performance and easily surpasses the accuracy of existing techniques.

Restoring End-to-End Resilience in the Presence of Middleboxes

The philosophy upon which the Internet was built places the intelligence close to the edge. As the Internet has matured, intermediate devices or middleboxes, such as firewalls or application gateways, have been introduced, thereby weakening the end-to-end nature of the network. As a result, applications must often modify their behavior to accommodate the middleboxes. This is is especially true in the case of transient failure of stateful devices. The failure of a middlebox causes it to lose the state it maintained, causing the failure of the associated TCP connections. Rather than assign the responsibility for recovery to applications, we incorporate a mechanism called an isolation boundary into TCP itself. The isolation boundary maintains a small amount of state across TCP connections, thus enabling reconnection. Furthermore, it does so without breaking backward compatibility with existing TCP. We present an implementation of the isolation boundary in the FreeBSD kernel and demonstrate its backward compatibility with TCP. We quantify the performance impact of the proposed mechanism on the establishment of new and resumed connections for both legacy and extended TCP stacks.

SLIM: Enabling Transparent Extensibility and Dynamic Configuration via Session-Layer Abstractions

Increasingly, communication requires more from the network stack, e.g., seamless handoff and synchronization of state between multiple participants. Due to the lack of support for desired functionality, networking libraries are created to fill the void. This leads to considerable duplication of effort and complicates cross-platform development. Furthermore, the means for extending legacy protocol stacks is largely exhausted (e.g., the TCP options space in the SYN message is mostly allocated), making the addition of future extensions much more challenging. In this paper, we tease apart elements of session management that are currently conflated with the transport semantics in TCP and highlight the need for sessions in contemporary communications. Next, we propose session, flow, and endpoint abstractions that lead to a clearer description of advanced communication models. This effort results in an extensible session-layer intermediary (SLIM) that leverages the above abstractions to support the additional functionality needed by modern applications, such as mobility, communication between two or more participants, and dynamic reconfiguration. SLIMs approach also provides the means for future extensibility of the network stack in a backward-compatible way, thus enabling incremental adoption.

Cascaded TCP: Applying pipelining to TCP for efficient communication over wide-area networks

The bandwidth utilization in traditional TCP protocols (e.g., TCP New Reno) suffers over high-latency and high-bandwidth links due to the inherent characteristics of TCP congestion control. Conventional methods of improving throughput cannot be applied per se for streaming applications. The challenge is exacerbated by “big data” applications such as with the Long Wavelength Array data that is generated at a rate of up to 4 terabytes per hour. To improve bandwidth utilization, we introduce layer-4 relay(s) that enable the pipelining of TCP connections. That is, a traditional end-to-end connection is split into independent streams, each with shorter latencies, that are then concatenated (or cascaded) together to form an equivalent end-to-end TCP connection. This addresses the root cause by decreasing the latency over which the congestion-control protocol operates. To understand when relays are beneficial, we present an analytical model, empirical data and its analyses, to validate our argument and to characterize the impact of latency and available bandwidth on throughput. We also provide insight into how relays may be setup to achieve better bandwidth utilization.