Yitzchak M. Gottlieb

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.

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.

GNU Radio-Based Digital Communications: Computational Analysis of a GMSK Transceiver

Significant progress has been made in the past twenty years on the implementation of software-defined radios (SDRs) based on general purpose processors (GPPs). In contrast, there has been limited work on the analysis of the computational requirements of such SDRs. Quantifying the signal processing complexity in SDR is critical to ensuring that the system has sufficient computational resources to support reliable digital communications. Our contribution is to analyze and measure the computational cost of a Gaussian minimum shift keying (GMSK) transceiver based on GNU Radio, a widely used GPP-based SDR. Further, we introduce GNU Radios working mechanism. To the best of our knowledge, our work is the first to provide detailed computational analysis of digital communications based on GNU Radio.

Policy-controlled dynamic spectrum access in multitiered mobile networks

Managed mobile ad hoc networks, such as tactical networks, are frequently implemented using multiple subnets, or tiers, so that nodes in one tier can communicate to nodes in another tier only through gateways that can communicate in both tiers. This structure imposes an extra burden on network planning personnel to plan and configure appropriate nodes as gateways between tiers taking into account the connectivity between tiers required to meet communication needs and the robustness required to deal with failures and mobility. This paper presents Net Communication Goals—a policy for specifying connectivity between tiers—and an implementation of a system for enforcing these policies. Using Net Communication Goals, or net goals, network planning personnel need only specify the required number of connections between tiers. These policies are then dynamically enforced within each tier, reconfiguring the frequencies used by network nodes to provide dynamic access to different parts of the available spectrum, thereby automatically maintaining the needed connectivity without manual intervention.

Mission-driven tactical network management

In the tactical military context, the network exists to support a mission. Consequently, part of the process of mission planning is to define the required network performance in terms of measurable quantities (metrics). These metrics, such as required message delivery rates, maximum acceptable latencies, and acceptable-loss thresholds are used to design the network. This paper presents the TITAN (Tactical Information Technologies for Assured Networks) Network Management System (NMS), which uses these metrics to manage the network as well. The TITAN NMS generates maintenance policies from the stated mission goals and the generated network plan. The maintenance policies describe the metrics to be measured, the acceptable values of those metrics and the actions to take on various levels of the management hierarchy when values of the metrics are not acceptable. If the policy-defined actions do not restore the network performance to acceptable levels, the TITAN NMS dynamically replans the network to meet the mission needs. We describe the TITAN NMS system and its application to the problem of automating the management of future military tactical networks, along with scenarios illustrating the operation of the system.

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.

Gateway selection in multitiered mobile ad hoc networks

Mobile ad-hoc networks, such as tactical networks, are frequently implemented using multiple subnets, or tiers, so that nodes in one tier can communicate to nodes in another tier only through gateways that can communicate in two of the tiers. The selection of the gateway nodes affects the robustness and performance of the connected subnets. This paper presents an algorithm for selecting gateways in multitiered networks. The algorithm selects gateway nodes based on the performance impact, both current and predicted, to the network traffic. The algorithm is tunable to respond to restrictions on the number of permitted gateways and the number of standby gateways desired. This paper describes an implementation of the algorithm that controls nodes in a simulated network and presents directions for future research.

MOSS: Gathering Names in Networks of Mobile Nodes

Nodes in mobile ad hoc networks (MANETs) act as routers by exchanging routing information to determine initial routes and to update those routes to account for node movement and failure. This ability of MANETs to self-form and self-heal makes them ideal for scenarios that require rapid deployment in areas with limited network infrastructure. However, their dynamic nature makes it challenging to implement naming and location services, as well as other services that traditionally require a fixed infrastructure. A naming service is highly desirable in networks, especially in dynamic networks like MANETs, since it allows accessing network resources by fixed names instead of volatile addresses. This paper presents multicast onomastic search (MOSS), which is a technique for implementing a distributed DNS server in a MANET using multicast addresses. Upon entering a network, a MOSS-enabled node joins a multicast group responsible for resolving the nodes name. The node can then respond to DNS queries for its name. MOSS allows a set of nodes in a MANET to provide a naming service that is resilient to node movement and reconfiguration. It also guarantees that, once routes have stabilized sufficiently, it is always possible to resolve the name of a node provided only that the node itself is reachable.

Managing high volume data for network attack detection using real-time flow filtering

In this paper, we present Real-Time Flow Filter (RTFF) -a system that adopts a middle ground between coarse-grained volume anomaly detection and deep packet inspection. RTFF was designed with the goal of scaling to high volume data feeds that are common in large Tier-1 ISP networks and providing rich, timely information on observed attacks. It is a software solution that is designed to run on off-the-shelf hardware platforms and incorporates a scalable data processing architecture along with lightweight analysis algorithms that make it suitable for deployment in large networks. RTFF also makes use of state of the art machine learning algorithms to construct attack models that can be used to detect as well as predict attacks.

On the application of cognitive network design to MANET Network Management

The requirement for resilient networks of the types envisioned in the NCW paradigm underscores the need for both a systematic network design tool and an adaptive network management system that implements the design and ensures that the design continues to support mission requirements when the network is in operation. The Cognitive Network Engineering Design and Analysis Tool (C-NEDAT), jointly developed by Telcordia and CERDEC, is an analytic design tool rooted in formal network science based approaches that can be used to rapidly create robust survivable MANET designs. The TITAN (Tactical Information Technology for Assured Networks) Network Management System (NMS), jointly developed by Telcordia and CERDEC, is a policy-driven network management system that enables automated management of tactical networks based on a given mission description. Typically, networks are designed based on a maneuver plan and the NMS automates the management of the resulting network by reconfiguring the network in real time based on monitored information and root cause analysis. However due to the unpredictable dynamics inherent in the military networking environment (e.g., loss of mission critical nodes, drastic deviations from the mission plan, etc), the NMS will encounter situations where the specified reconfiguration actions cannot restore the network state to one where mission requirements are met. Such a situation calls for a dynamic re-design based on the actual network state to provide a new configuration that can meet the mission requirements, which can be instantiated by the NMS. We address this critical need and provide, in this paper, a novel real-time application of C-NEDAT to complement the network management function of TITAN by providing the ability to re-design the network in real-time in order to meet the mission requirements.