Kaustubh S. Phanse

Evaluation of Queueing Policies and Forwarding Strategies for Routing in Intermittently Connected Networks

Delay tolerant networking (DTN), and more specifically the subset known as intermittently connected networking, is emerging as a solution for supporting asynchronous data transfers in challenging environments where a fully connected end-to-end path between a source and destination may never exist. Message delivery in such networks is enabled via scheduled or opportunistic communication based on transitive local connectivity among nodes influenced by factors such as node mobility. Given the inherently store-and-forward and opportunistic nature of the DTN architecture, the choice of buffer management policies and message forwarding strategies can have a major impact on system performance. In this paper, we propose and evaluate different combinations of queueing policies and forwarding strategies for intermittently connected networks. We show that a probabilistic routing approach along with the correct choice of buffer management policy and forwarding strategy can result in much performance improvements in terms of message delivery, overhead and end-to-end delay

Design and demonstration of policy-based management in a multi-hop ad hoc network

Quality of service (QoS) provisioning and management in ad hoc networks remains a challenging task. Policy-Based Network Management (PBNM) is one approach for QoS provisioning and management that h ...

Addressing the requirements of QoS management for wireless ad hoc networks

Quality of Service (QoS) provisioning and management in ad hoc networks remains a challenging task. Existing research focuses either on providing QoS or on network management, in ad hoc networks. However, a comprehensive approach to QoS management in ad hoc networks, i.e. network management in support of service differentiation, QoS robustness, and network survivability is still lacking. In this paper, we survey the existing literature on ad hoc network management from a QoS perspective. We identify policy-based management as a promising approach for QoS provisioning and management in ad hoc networks, and describe the components that we believe are crucial for effective functioning of such a policy-based framework. Our initial experimental results in assessing signaling overhead and response time for network management in ad hoc networks support the choice of a hybrid policy architecture that combines outsourcing and provisioning policy distribution models.

Protocol support for policy-based management of mobile ad hoc networks

The management of mobile ad hoc networks (MANETs) is a challenging task. Previous work on this topic has focused largely on the monitoring and data collection aspects of network management; literature on the provisioning of devices and protocol support for MANET configuration is scarce. We present a solution suite to extend policy-based management, for the first time, to MANETs. The solution suite consists of four schemes - k-hop clustering, dynamic service redundancy (DynaSeR), policy negotiation, and automated service discovery - each addressing different challenges in managing ad hoc networks. We propose extensions to the standard common open policy service (COPS) protocol for use in MANETs, and evaluate the system performance using simulations.

Opportunistic wireless access networks

Today, intermittent connectivity is common in wireless access networks and it seems like mobile users will have to deal with discontinuous network access in the future. But existing network protocol architectures are not resilient to disruption of communication links and often communication fails when faced with sporadic connectivity. We discuss a new paradigm for wireless access called opportunistic collaborative networking, where communication is disruption-tolerant and wireless devices exploit any opportunity of communication, albeit temporary, to forward messages towards the destination. For developing protocols for these innovative networks requires understanding of their structure and dynamics. We present some results from analysis of real-life traces representing two such mobile network environments with ad-hoc, intermittent connectivity.

Characterization of performance of TCP/IP over PPP and ATM over asymmetric links

The objective of this paper is to characterize and analyze the performance of TCP/IP when used over point-to-point protocol (PPP) and asynchronous transfer mode (ATM) on asymmetric links. This will allow us to gain insight into this new protocol architecture used in the asymmetric digital subscriber line (ADSL) access network and to investigate the related quality of service (QoS) issues. Using simulation, we verified the effects of asymmetry on the performance of TCP and additional throughput degradation caused by segmentation at the ATM layer. This study was done for unidirectional and bidirectional data transfer using different traffic mixes. We also quantified the improvement in the downstream throughput obtained by delaying the TCP acknowledgements and using TCP/IP header compression. Although these techniques are effective for unidirectional TCP/IP data transfer over asymmetric links, they do not prove as effective for bidirectional traffic, and the problem further exacerbates when ATM enters the scenario. Hence, there is a need for additional enhancements in such scenarios. Further, we modified the existing protocol stack model to implement PPP encapsulation over the ATM adaptation layer (AAL5). We characterized and analyzed the effect of the additional PPP overhead on system performance in terms of throughput degradation and additional delay. We also evaluated the use of TCP/IP header compression for improving performance in presence of PPP encapsulation.

Modeling and Evaluation of a Policy Provisioning Architecture for Mobile Ad-Hoc Networks

The ability to dynamically configure mobile ad-hoc network (MANET) devices is critical for supporting complex services such as quality of service (QoS), security and access control in these networks. In our work, we address the problem of policy distribution and provisioning in MANETs. Previously, we have proposed a policy provisioning architecture that enables the operator, e.g., a military command and control center, to maintain a logically centralized control of the network as a whole, while allowing a physically decentralized and self-managing implementation essential for a MANET environment. In this paper, we present an analytical model of the availability of the policy distribution service in a MANET and analyze the performance using stochastic Petri nets (SPNs). We develop the model at two levels of complexity: as a simple Markovian model with Poisson assumptions and as a more accurate non-Markovian model with general distributions obtained using statistical parameterization. We compare and cross-validate the analytical results with simulation and experimental results. Finally, we illustrate the effectiveness of the architecture for managing QoS for soft real-time applications, using an emulated mobile ad-hoc network testbed.

Effects of competing traffic on the performance of TCP/IP over asymmetric links

We analyze and characterize the performance of TCP/IP over the point-to-point protocol (PPP) over ATM using asymmetric links in the presence of multiple clients competing for bandwidth. This is part of an ongoing research project that studies techniques to provide end-to-end quality of service to flows when ADSL is used in the access network. The results presented illustrate the decrease in fairness and the link utilization that occurs in the presence of both bi-directional and unidirectional flows in an ADSL environment.

Traffic management for voice/data convergence in ADSL

Asymmetric Digital Subseriber Line (ADSL) is one of the leading technologies to enable the convergence of voice and data in the last mile. Much effort has been put into the development of voice over DSL (VoDSL) solutions that efficiently harness the bandwidth available in existing copper infrastructure in the local loop for the transmission of high-speed data as well as multiple voice calls. In this paper, we address the different VoDSL architectures that are being considered. We then present simulation results pertaining to acknowledgment filtering and regeneration, which have the potential to significantly improve data throughput over asymmetric links. Finally, we argue for queuing and scheduling mechanisms to separate data from acknowledgement traffic; our preliminary results show that service differentiation is key in obtaining good TCP performance in the presence of bidirectional data traffic over ADSL. This may lead to a hierarchical scheduling scheme when voice traffic is added to the mix.

ExPLoIT: Exploiting Past Location Information and Transitivity for positioning in mobile sensor networks

We present a novel distributed range-free technique called ExPLoIT for estimating geographical location of sensor nodes in mobile sensor networks. ExPLoIT is the first positioning technique that exploits location information at regular nodes in addition to using seeds. The key idea is the notion of confidence that a node has in its location estimate which can be used by other nodes for localization. Using Monte Carlo integration, a node estimates its current location and confidence based on its past location and the location information it receives from its neighbors. Node mobility is exploited to transitively localize the network. Our extensive simulation study shows that our proposal outperforms three other state-of-the-art range-free localization techniques under a wide range of conditions. The strength of ExPLoIT is that it is robust to irregular radio propagation, arbitrary seed and node density, and stochastic seed and node mobility; no special hardware is necessary at sensor nodes.