Gary Levin

Policy-based mobile ad hoc network management

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 reconfiguration 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.

Declarative Infrastructure Configuration Synthesis and Debugging

There is a large conceptual gap between end-to-end infrastructure requirements and detailed component configuration implementing those requirements. Today, this gap is manually bridged so large numbers of configuration errors are made. Their adverse effects on infrastructure security, availability, and cost of ownership are well documented. This paper presents ConfigAssure to help automatically bridge the above gap. It proposes solutions to four fundamental problems: specification, configuration synthesis, configuration error diagnosis, and configuration error repair. Central to ConfigAssure is a Requirement Solver. It takes as input a configuration database containing variables, and a requirement as a first-order logic constraint in finite domains. The Solver tries to compute as output, values for variables that make the requirement true of the database when instantiated with these values. If unable to do so, it computes a proof of unsolvability. The Requirement Solver is used in different ways to solve the above problems. The Requirement Solver is implemented with Kodkod, a SAT-based model finder for first-order logic. While any requirement can be directly encoded in Kodkod, parts of it can often be solved much more efficiently by non model-finding methods using information available in the configuration database. Solving these parts and simplifying can yield a reduced constraint that truly requires the power of model-finding. To implement this plan, a quantifier-free form, QFF, is defined. A QFF is a Boolean combination of simple arithmetic constraints on integers. A requirement is specified by defining a partial evaluator that transforms it into an equivalent QFF. This QFF is efficiently solved by Kodkod. The partial evaluator is implemented in Prolog. ConfigAssure is shown to be natural and scalable in the context of a realistic, secure and fault-tolerant datacenter.

Computing diagnostic explanations of network faults from monitoring data

Network fault diagnosis is an important aspect of network management. Often, a single component failure will result in a cascade of secondary faults that overwhelm simple reasoning approaches. If the network monitoring information is being transmitted through the network to the network management system (NMS), then fault diagnosis is complicated by the fact that the transmission of relevant monitoring information for fault diagnosis may be blocked either by the fault itself, or by the faultpsilas effects on the network. Without perfect knowledge, the best fault diagnosis algorithm must properly reason about a number of competing diagnostic explanations that are compatible with the ambiguous networking monitoring information known to the NMS. We describe a novel algorithm for computing all such possible diagnostic explanations and their relative likelihoods, thus providing a complete diagnosis of the network state that can be effectively used by an NMS to correct or mitigate faults. The algorithm uses a variant of classic Boolean satisfiability to efficiently and compactly represent the space of possible explanations. The proposed approach is well suited for networks with (semi-)autonomous management domains organized into a larger management hierarchy, a feature common to many military networks.

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.

PECAN: policy-enabled configuration across networks

The Internet is growing to the point of needing more serious, scalable management infrastructure. Telecommunications companies and Internet service providers alike face the pressures of upgrading and provisioning their networks while constraining their infrastructure costs to maintain profitability and to stay competitive in an industry that is financially stressed with tight profit margins. In order to be financially successful in this environment, service providers will have to support a variety of services and applications on a combined packet infrastructure, carrying increased varieties of traffic with different performance characteristics and predictable levels of managed quality of service (QoS). Multi-protocol label switching (MPLS) traffic engineering enables service providers to engineer their networks to provide such QoS; however, this task brings along with it a plethora of management challenges. We discuss these management challenges and our experience with the design and implementation of a policy-based management system, PECAN, for managing MPLS networks. PECAN provides the ability for a network operator to define high-level policies that control the operation of the management system. These high-level policies control admission of traffic into the network based on the QoS guarantees required; placement of traffic flows on MPLS traffic engineered paths; and the feedback loop between network fault/performance monitoring and reconfiguration of the network to alleviate the effects of any observed problems.

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.

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.