Kashif Munir

Grid Network Dimensioning by Modeling the Deadline Constrained Bulk Data Transfers

Grid applications need to move large amounts of data between distributed resources within deterministic timeframes. In most cases it is possible to specify the volume and the deadline in advance. We formally define and analyze a mechanism of network reservations of bulk data transfer requests having opportunistic utilization of residual network capacity and analyze it using an M/M/1/N-RPS queue. We compare the analytical results of our mechanism with the analytical results obtained from an M/M/N/N queue, for the case in which there is no opportunistic sharing of residual capacity. We validate the analytical results through simulations in C++. The analytical model is also validated against ns-2 simulations taking into account network level details (IP and TCP protocols), showing remarkably good coherence even under heavy loads. The model is orders of magnitude faster than simulation, which enables its application for capacity planning of Grid networks (also known as network dimensioning), and to enforce Connection Admission Control (CAC) under the practical hypothesis of a dominating bottleneck on the transfer route.

Using an Event Based Priority Queue for Reliable and Opportunistic Scheduling of Bulk Data Transfers in Grid Networks

This paper proposes an opportunistic, reliable and realistic QoS mechanism for bulk data transfers in grids, which maximizes acceptance rate and network resource utilization by using an event based priority queue. The metrics that have been studied in the evaluation of elastic scheduling heuristics are the acceptance percentage and the mean flow time of requests. Some of the existing heuristics for the scheduling of bandwidth requests do not include the communication and computation delays and communication overheads, which are involved in the reliable transfers of such reservations. We have compared our approach with only those existing heuristics which are reliable and include all overheads. We demonstrate the performance improvement by documenting results of simulations.

A Bounded Model Checking Approach for the Verification of Web Services Composition

In this paper, we propose a bounded model-checking based approach for the verification of declarative Web services composition processes using satisfiability solving SAT. The need for the bounded model-checking approach stems from the nature of declarative processes as they are defined by only specifying the constraints that mark the boundary of the solution to the composition process. The proposed approach relies on using Event Calculus EC as the modeling formalism with a sound and complete EC to SAT encoding process. The use of EC as the modeling also formalism allows for a highly expressive approach for both the specification of composition model and for the specification of verification properties. Furthermore, as the conflict clauses returned by the SAT solver can be significantly large for complex processes and verification requirements, we propose a filtering criterion and defined patterns for identifying the clauses of interest for process verification.

Performance analysis of mobility management architectures in cellular networks

Flattened cellular network architecture for the mobile internet is expected to meet the demands of rapidly increasing traffic from mobile users. Dynamic mobility anchoring (DMA) mechanism distributes the mobility management functions using such network architecture. In this paper, we compare DMA with a classical mobility protocol like proxy mobile IP (PMIP). A major cost factor of a mobility protocol is the management of contexts and tunnels. We propose an analytical model to compute the number of contexts and tunnels with DMA and with PMIP in a homogeneous network with random mobility of mobile nodes. The model is used under different configurations by varying the traffic loads and the capacities of access nodes in order to analyze the distributed and dynamic characteristics of DMA. The results show that the required number of contexts on an anchor node with DMA is significantly less than that required on an anchor node with PMIP and the required number of visitor contexts with DMA is significantly less in magnitude than that with PMIP for most of the configurations. The results also show that the number of required tunnels with DMA is less than those required with PMIP for most configurations.

Planning data transfers in grids: a multi-service queueing approach

Grid applications move large amounts of data between distributed resources, and the efficiency of a Grid depends on their timely delivery within given bounds (deadlines). In most cases, the data volume and deadline are known in advance, allowing for both network planning and connection admission control (textrmCAC). We formally define the problem and, based on this formalization, describe the operation of a feasible procedure for network reservations of deadline‐constrained bulk data transfer requests. The procedure guarantees a minimum bandwidth to meet the deadlines and allows for opportunistic utilization of residual network capacity. We propose a novel analytical model based on the solution of an M/M(nc)/1/k(s)−RPS queue. The analytical model is validated against ns−2 simulations taking into account network level details (IP and TCP protocols), showing remarkably good coherence even under heavy loads. The model is orders of magnitude faster than simulation, which enables its application to plan the capacity of Grid networks, and to enforce CAC under the hypothesis of a dominating bottleneck on the transfer route. Copyright

Combining explicit admission control and congestion control for predictable data transfers in grids

To improve the Grid infrastructures efficiency, the co-reservation of distributed resources is often required. Therefore, Grid applications need to move large amounts of data between these resources within deterministic time frames. In most cases it is possible to specify the volume and the deadline in advance. This paper proposes an approach for data-movement management and bandwidth reservation in Grid, which provides a high acceptance probability of flows in the network while maintaining efficient network-resource utilization. To achieve this, our proposal combines explicit admission control and high-speed transport protocols to enable an opportunistic sharing of the capacity by flows having heterogeneous bandwidth and delay requirements. We formulate the problem and discuss several objective functions. Then we present different heuristics and evaluate them according to the requests acceptance rate and the networks utilization metrics. Our simulations include all the communication and computation overheads which are involved in such data transfers.

AN EVENT‐BASED APPROACH FOR DECLARATIVE, INTEGRATED AND SELF‐HEALING WEB SERVICES COMPOSITION

Web services are defined to be the software systems that provide interoperable machine‐to‐machine interaction over a network. Individual services may need to be composed and the composition process design, verification and monitoring are thus active and widely studied research directions. However, the traditional approaches are both procedural (and rigid) and do not address the need of integrating these related dimensions using a unified formalism. In this paper, we propose an event‐oriented framework called DISC that is both declarative and serves as a unified framework to bridge the gap between the process design, verification and monitoring. It provides a flexible and highly expressive composition design that can accommodate various aspects such as data relationships and constraints, Web services dynamic binding, compliance regulations, security or temporal requirements etc. Furthermore, the DISC framework allows for instantiating and verifying the composition design and for monitoring the process while in execution.

Performance prediction of a weighted capacity sharing scheme for grid bulk data transfers using a multi-service queue

Applications in high-speed networks like Grids often require to transfer large volumes of data to remote locations under certain time constraints. This requires a network reservation, mechanism for the large data transfer requests. It is possible that some network capacity is available even after fulfilling the capacity requirements of the requests. The sharing of the available network capacity, called residual capacity, has direct impact on the actual time taken to serve a request. In this paper, we propose a novel weighted capacity sharing model to predict the performance of the deadline-constrained data transfers. A weighted sharing scheme is desirable since a request with higher capacity requirement should get higher share of the residual capacity than that of a request with lower capacity requirement in order to reduce its transfer time. We calculate the blocking probabilities and mean flow time using our scheme and compare the results with an existing scheme of equal residual capacity sharing. The results show that weighted-sharing scheme is better than equal capacity-sharing scheme as it reduces the mean transfer time of requests of a higher capacity requirement class. We also validate the model through simulations.