Shihwei Li

Performance Analysis of Drama: A Distributed Policy-Based System for Manet Management

DRAMA is a distributed policy-based management system designed to manage mobile ad hoc networks (MANETs). Its design philosophy is to create intelligent, self-adaptive policy agents to manage dynamic networks without human intervention. Network management functions are performed in a distributed fashion by these policy agents, rather than being controlled by a centralized management station. Policies are used to control the frequency and content of network management messages exchanged among policy agents in a way that reduces bandwidth usage and increases the utility of management messages. This greatly enhances management efficiency and reduces the bandwidth overhead required for network management. As with any new technology, there is a question about the scalability of this approach. The purpose of the work described in this paper is to study whether the DRAMA policy-based network management system can scale to networks of 500+ nodes. The study uses a novel simulation-based approach to evaluate DRAMA performance when DRAMA is used to manage MANETs of up to 500 nodes. The results confirm that the DRAMA distributed policy-based management paradigm provides superior performance over a centralized management paradigm for MANETs

Policy-based mobile ad hoc network management for drama

Ad hoc networking is the basis of the future military network-centric warfare architecture. Such networks are highly dynamic in nature, as mobile ad hoc networks are formed over wireless links that are susceptible to failure. Strict requirements on security and reliability combined with the dynamic nature of the network provide a strong motivation for self-forming, self-configuring, and self-healing capabilities in the network. This paper describes a policy-based mobile ad hoc network management system that addresses these needs. The system provides the capability to express networking requirements in the form of policies at a high level and have them automatically realized in the network by intelligent agents. Our system provides the following capabilities: flexible monitoring and reporting that enables collection of management information from network elements at configurable intervals; automated configuration and re-configuration of network elements based on reported network status; user-definable aggregation and filtering of monitored management information at the source of the data so as to reduce management station processing and network transmission overhead.

Scalable policy management for ad hoc networks

The characteristics of mobile ad hoc networks (commonly called MANETs) are sufficiently different from commercial wireline networks to have generated a great deal of work in alternate management paradigms. The task of managing MANETs involves frequent reconfiguration, due to node mobility and consequently dynamically changing network topology. Network nodes often have limited battery power and storage capacity, and wireless radio link capacity and quality varies dynamically based on environmental conditions (weather, terrain, foliage, etc.). These differences have resulted in a need for paradigms particularly suited for managing MANETs. In this paper, we describe a distributed, hierarchical management system that implements policy-based control of a MANET. Policies are used to enable flexible composition of diverse management actions based on network conditions and external events. A policy conflict detection mechanism based on event calculus is used to detect certain types of policy conflicts. The rapidly changing network topology and link characteristics typical of a MANET are managed by an adaptive, self-forming hierarchy of policy agents that implement the appropriate management actions based on their management role. The system described in this paper has been prototyped and demonstrated in a laboratory environment

On Automated Policy Generation for Mobile Ad Hoc Networks

In this paper we describe an approach to the problem of automated policy generation for mobile ad hoc networks. The automated policy generation problem is difficult in its own right. It becomes even more challenging when the context environment to consider is a mobile ad hoc network. We have designed an optimization-based, utility-driven approach aimed at generating optimal policies with respect to the given network objectives. The main novelty of this approach is in the combination of optimization heuristics and network simulation to solve the problem. We describe this approach, present the software architecture of our implementation, and illustrate the approach with a case study on automated generation of DiffServ-based QoS policies for a 50-node mobile ad hoc network.

QoS-aware Adaptive Middleware (QAM) for tactical MANET applications

Developing distributed applications for MANETs is a complex task due to the latters bandwidth constrained nature. Further, in tactical MANETs, there is a need to prioritize traffic generated by distributed applications so that high priority traffic gets preferential access to the bandwidth constrained communication medium. Finally, applications must be designed to accommodate network bandwidth and traffic loads that vary with time. It is unrealistic to expect individual application developers to be able to accommodate these constraints which essentially cut across multiple applications that share the MANET. In this paper we describe a communication middleware system: QoS-aware Adaptive Middleware (QAM) that shields distributed application developers from the complexities of tactical MANETs1. QAM resolves the problem of bandwidth contention between multi-priority applications by providing an adaptive, priority aware, middleware layer that acts as an intermediary between an application and the network protocols it uses. QAM adapts to current network conditions by providing a reliable data transfer mechanism that is capable of adapting data transfer rates in response to changing network conditions. The adaptations performed by QAM attempt to limit the use of network bandwidth by applications when network bandwidth is diminished. Moreover, QAM limits network use more aggressively for lower priority applications than for higher priority applications, thus giving preferential treatment to the latter. Existing network layer mechanisms such as priority queuing and bandwidth provisioning are either inadequate or inapplicable for addressing traffic prioritization needs in tactical MANETs. QAM provides capabilities that are complementary to existing QoS mechanisms and is better suited for tactical MANETs. Our paper provides a description of the QAM architecture and early evaluations of a QAM prototype.

AMS: an adaptive middleware system for wireless ad hoc networks

The characteristics of ad hoc networks greatly increase the complexity of programming distributed applications with respect to both sending and receiving messages. This is because the network programming API based upon TCP and UDP was designed for the relatively stable, stationary Internet. The semantics of the API does not address the emerging issues from the dynamic mobile wireless ad hoc networks. One promising approach for alleviating this problem is to develop applications on top of a middleware system to shield applications from dealing with the dynamics of ad hoc networks. However, conventional middleware systems were not designed to cope with the frequently changing communications characteristics of military ad hoc networks. In order to address the above problem, we have designed and implemented a prototype of AMS , an Adaptive Middleware System with the following features. First, this middleware system is specifically designed to deal with dynamic and unreliable networks. Second, it shields communicating entities from coping with frequently changing networks via an API with semantics that provide a suitable abstraction of the underlying dynamic networks. Third, it allows individual applications to define their own communications requirements while the middleware system can set the lowest common requirements for all the communications per the military situations. Lastly, this middleware system has an interface that allows an external control system to adjust the values of its parameters to optimize the overall system performance.

Novel software agent framework with embedded policy control

In general, agent frameworks allow the functionality of their agents to be augmented with plug-ins, and agents in a multi-agent system collaborate with other agents to achieve their collective and/or individual goals. This model poses a few issues in terms of function coordination: (i) to allow the insertions of plug-ins on-the-fly, an agent framework needs to properly schedule the execution of plug-ins in a timely, coordinated fashion; (ii) plug-ins may conflict with each other in their behavior; and (in) agents may need to adapt their behavior based on their environments, in addition to coordinating their actions according to their objectives. Recent advances in policy-based management research suggest a promising direction to remedy the deficiency of existing software agent frameworks. We envision that the coordination between the plug-ins within an agent as well as the compliance of agents with environmental requirements can be achieved via policy control. With policy control, agents can adapt their behavior dynamically to meet the ever-changing environmental requirements such as those posed by military wireless ad hoc networks. In this paper, we present a novel software agent framework with seamlessly integrated policy control. We first describe the concept of policy control and how it is integrated into this framework. Next we explain the process of policy in action, discuss in detail the functions and benefits of policy control, and elaborate on the agent behavior adaptation that enables agents to achieve their goals while meeting dynamic environmental requirements.

Enabling Distributed Management for Dynamic Airborne Networks

In this paper we describe our experience with integrating a distributed policy-based management system (DRAMA) with an open-source network management system (OpenNMS) 1 . Network operations seeking the benefits of policy-based network management often have pre-existing network monitoring systems. While these pre-existing systems are capable of monitoring the network, they are limited in their: 1) ability to provide distributed network management, 2)support for automatically reconfiguring the network in response to network events, and 3) ability to adjust management traffic bandwidth consumption based on network conditions. For dynamic networks such as those consisting of airborne platforms, there is a need to provide the above capabilities in any management solution while preserving any underlying management systems. As a result, we integrated DRAMA with OpenNMS to add distributed policy management capability to a commonly used network management system. In this paper, we describe the background for this effort, our approach for integrating OpenNMS with DRAMA, and the design of a distributed resource indirection framework that allows the use of the same policies across different distributed policy decision points managing network devices with different attribute values.

An Automated Policy Generation System for Mobile Ad Hoc Networks

In this paper, we describe an approach to the problem of automated policy generation for mobile ad hoc networks. The automated policy generation problem is difficult in its own right. It becomes even more challenging when the context environment to consider is a mobile ad hoc network. We designed an optimization-based, utility-driven approach aimed at generating optimal policies with respect to the given network objectives. The main novelty of this approach is in the combination of optimization heuristics and network simulation to solve the problem. We describe this approach, present the software architecture of our implementation, and illustrate this approach with a case study on automated generation of DiffServ-based QoS policies for a 50-node mobile ad hoc network.