Cho-Yu Jason Chiang

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

An integrated testbed for Virtual Ad Hoc Networks

Testing of applications for ad hoc networks poses a special technical challenge due to the difficulty of conducting experiments in an ad hoc network environment at a scale larger than a few nodes. One approach is to conduct experiments in a testbed that can imitate an ad hoc network. This requires the development of technologies that enable multiple instances of unmodified application software on a set of hosts to communicate via a simulated network that behaves like a real ad hoc network. In this paper, we describe the testbed developed under the Virtual Ad hoc Network (VAN) project1 for testing applications over ad hoc networks, with a special focus on network management applications. The testbed employs Xen-based virtualization to achieve resource scalability. The infrastructure for the testbed provides an integrated platform consisting of virtual nodes running the actual software under test, augmented with a simulated network environment. Our goal is to enable software testing over large-scale (500–1000 nodes) ad hoc networks using the VAN Testbed.

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.

DRAMA: Distributed Policy Management for MANETs

This demonstration will showcase the capabilities of DRAMA [Chadha, R. et al., 2004, Chiang, C. et al., 2005 ], a distributed policy-based network management system for mobile ad hoc networks (MANETs). This system was developed with a specific emphasis on supporting the dynamic nature of MANETs. In particular, an instance of DRAMA is placed on every node in the network, and these distributed instances autonomously organize themselves into a hierarchy of managers that cooperate to manage the network. DRAMA has been shown to be very effective in managing MANETs, which are characterized by scarce bandwidth, due to its ability to adapt its use of network bandwidth to network conditions based on specified policies.

Generic protocol for network management data collection and dissemination

YAP is a protocol designed to efficiently and robustly relay network configuration states of nodes to a designated node that collects and stores the configuration states of all the nodes. Once the configuration states from the nodes are collected, any application can query the information to perform its own specific function. For example, a GUI application can query the database to display the logical topology of the networks. Also a Configuration Manager can query the database to decide how to reconfigure the network. We describe how YAP was integrated with protocols designed to auto-configure IP-related attributes of nodes (using DRCP and DCDP).

Issues with and approaches to network monitoring and problem remediation in military tactical networks

This paper describes an approach to root cause analysis and fault correlation that addresses the problems inherent in wireless military networks.1 Root cause analysis concerns itself with identifying and correcting problems in a network. The ultimate goal of root cause analysis is to diagnose the cause for network anomalies, towards the ultimate goal of ensuring that adequate communication functionality is maintained to support the requirements of the network users. In a wired network, the diagnosis of faults is easier due to the existence of a fixed, wired topology and fixed, wired links. In the wireless networks at the tactical edge of military networks, there is no hardwired connectivity, yet there are also expectations on the network from the end users which place constraints on the operation of the network. Fault diagnosis in such networks is fundamentally different from that in wired networks. The performance of the network must be managed explicitly with respect to its user expectations, even though the network connectivity is dynamic, the network monitoring traffic must traverse the (possibly failing) network itself, and the “correct” behavior of the network against which current network state needs to be compared evolves over time. The novel features of our solution that distinguish it from existing root cause analysis techniques are (a) a dynamic model of fault, performance and security problem propagation in the network that can evolve as the definition of network correctness changes, (b) a method for distributing reasoning over this model throughout the network into independent Correlators that share information through a set of Clearinghouses to provide a global root cause correlation capability, and (c) the ability for the Correlator and Clearinghouse reasoning to adapt gracefully when network problems prevent full exchange of information required for root cause analysis.

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.