Brian Adamson

Evaluation of distributed cover set algorithms in mobile ad hoc network for simplified multicast forwarding

This paper presents design issues and performance analysis of optimized cover set algorithms supporting Simplified Multicast Forwarding (SMF) of data plane traffic within mobile ad hoc network (MANET) environments. SMF is presently being developed within the Internet Engineering Task Force (IETF) as an experimental specification to provide simplified multicast data dissemination among multi-hop, wireless nodes within peer MANET routing neighborhoods. The SMF protocol allows for a variety of cover set reduction techniques to optimize the simplified data flooding and relaying process amongst routing peers. A variety of distributed algorithms for forming connected dominating sets (CDS) are being considered as mechanisms to reduce the cover set. This paper presents modeling and analysis work of various CDS relay set algorithms and demonstrates working code within an SMF implementation. We provide a brief problem background, discuss models and scenarios, compare various algorithms, and then summarize observations as well as discuss future work. A main purpose of the paper is to begin examining the robustness of the algorithms to mobility and increasing multicast traffic load. We examine the results against a classical flooding baseline for comparison. We observe similar efficiency and robustness performance for several forwarding algorithms of interest.

Integration of the CORE and EMANE Network Emulators

Researchers who evaluate networking protocols and applications can benefit significantly from the availability of flexible, open source tools. Network emulation has been one of the tools of choice for conducting experiments on commodity hardware, and for wireless MANET environments, in the absence of a possibly large number of radio devices. We present an easy-to-use system based on a combination of two such open source emulation tools. We describe integrating the Common Open Research Emulator (CORE), providing virtualization controlled by a graphical user interface, with the Extendable Mobile Ad-hoc Network Emulator (EMANE) framework that provides for more detailed radio models and scenarios. We discuss the benefits of integrating the two tools, along with challenges of this approach and how they were addressed. We address the performance experienced when using these more detailed link- and physical-layer models. Finally, we conclude with open issues and future directions.

Mobile Ad Hoc Network emulation environment

To support research in wireless mobile ad hoc networks, the U.S. Army Research Laboratory (ARL) and Naval Research Laboratory (NRL) have worked jointly to establish an advanced emulation environment. A key component is a Mobile Ad-Hoc Network emulation testbed where algorithms and applications can be subjected to representative wireless network conditions. The testbed is based on a version of the “MANE” (Mobile Ad hoc Network Emulator) software originally developed by the Naval Research Laboratory (NRL). Consulting & Engineering Next Generation Networks (CENGEN) has enhanced MANE by implementing a modular, extensible architecture which allows advanced modeling methods and computing technologies to be incorporated into the environment. This paper discuses the current capabilities of Mobile Network Emulation for conducting empirical evaluation and demonstration of MANET technologies and is organized into 5 sections: (1) introduction to the role of emulation in network modeling, (2) mobile network emulators background (3) emulation system components (4) future plans and (5) conclusions.

AgentJ: Enabling Java NS-2 Simulations for Large Scale Distributed Multimedia Applications

We present a framework, called AgentJ that extends the NS-2 platform to support the simulation and performance analysis of Java network applications. We particularly focus on the simulation of P2P networks and have already integrated the P2PS middleware for the simulation of super-peer networks for discovering participants in large scale Internet applications, which has a high significance for distributed multimedia applications to enable overlays for the discovery and searching across large numbers of distributed multimedia resources. AgentJ builds upon the numerous years of networking research with NS-2 and leverages the Protolib toolkit from NRL to facilitate the passing of real data between NS-2 nodes, thereby creating a platform for the simulation of content-based middleware and applications. AgentJ currently supports UDP unicast and multicast and maintains compatible programming interfaces with the standard Java network package as well as the NS-2 scripting interfaces employed for staging simulations

Reliable messaging for tactical group communication

Command and Control and other applications operating in tactical edge networks often require group-wise communication to effectively support military operations. Tactical users rely upon group situational awareness. Mission planning and execution involves distributing force orders and supporting information among collaborating groups. Network-centric concepts of operation offer the promise of a more flexible and responsive fighting force if the necessary information can be effectively disseminated and exchanged among warfighting users and elements. The Naval Research Laboratory (NRL) has conducted research and development of reliable multicast transport protocols for over a decade. The NACK-Oriented Reliable Multicast (NORM) protocol specification provides robust reliable transport and ancillary functions to support different application needs. The NRL NORM “toolkit” implementation provides controls for application developers to develop robust and efficient group messaging applications capable of operating in tactical edge network environments. This paper describes these mechanisms and presents some results from laboratory and field experiments.

Mitigating naval network instabilities with disruption toler

We describe an approach to improving network performance in networks with heterogeneous links - for example, a communications network constructed from satellite links, airborne relays, and line-of-site radios - using disruption tolerant networking. DTN defines an overlay network that uses storage at each hop to make end-to-end communications resilient to delay, loss, network disruption, temporary network partitioning, and congestion. DTN further improves performance by allowing separate transport layers at each hop of the overlay that can be tuned for the local network environments. We present recent work interfacing one such transport layer, the NACK oriented reliable multicast (NORM) protocol, to DTN; performance experiments from tactical radios; and simulation results based on models of deployed systems.

Elastic multicast for tactical communications

This paper presents a multicast routing mechanism supporting the classical IP multicast service model that can dynamically use redundant forwarding in the parts of the network affected by a high rate of topology changes, while converging to regular multicast distribution trees where or when the network becomes relatively stable. The rationale is that intermittent connectivity directly affects the ability of routers to synchronize on their view of the network, thus making it difficult to converge on efficient distribution trees, while network wide broadcast may be prohibitively expensive for relatively sparse groups. We describe a hybrid approach, called Elastic Multicast, which dynamically expands to limited scope broadcast when needed, and converges single path forwarding if the network is stable, through independent routing decisions made at each node.

Temporal stability for dynamic network relay sets

Distributed relay set election instability within mobile networks can cause backbone topology changes that affect the performance of both unicast and multicast data routing algorithms. We discuss stability improvements to such relay set election by adding a “resistance to change” weighting factor to help reduce change in election results. In particular, we examine a proposed extension to the Essential Connected Dominating Set (ECDS) algorithm that has been specified for use by both present mobile ad hoc network unicast and multicast protocols. We demonstrate temporal stability improvements in the ECDS relay set membership that can be achieved with a simple modification to the election algorithm. Our results are particularly important when dealing with frequently changing election metrics represented in the priority field such as density or link quality as a weight metric. By using several mobile models of networks undergoing link quality fluctuations we demonstrate significant improvements in stability of the backbone set. Our results also indicate that we can maintain good stability results while maintaining a small relay set membership size as compared to the unmodified algorithm.

Experiment and field demonstration of serverless group communication

This paper presents a field experimentation and demonstration addressing serverless information services that provide both group messaging with ordering guarantees and robust file/media object sharing in a tactical edge communication environment. These serverless information services constitute the main functional components of our real time image and ordered annotation sharing application, called Tactigram. The purpose of Tactigram is to integrate serverless services in useful tool demonstrating the utility of real time information exchange to the warfighter. We show how a Group Communication Service (GCS) framework provides for quick exchange of small data, and tactical torrents (SISTO) provide for file sharing used by Tactigram. The demonstration was conducted as part of the Agile Bloodhound 2014 (AB14) field event. In accordance with AB14 use case scenarios, Android devices were used to exchange images and annotations over Soldier Radio Waveform (SRW) and WiFi MANETs in fully distributed manner. While the results obtained constitute a very preliminary evaluation of serverless group communication, the field test environment was very useful in highlighting critical design points (e.g., on-the-move dynamics) where enhancements of the protocol are needed.

Mobile Network Emulation -- Experiences and Challenges

The development and use of emulation-based modeling of wireless, mobile network systems have matured during the past several years. This approach to experimentation has had several successful applications and a growing community of researchers has been collaborating to advance this technology. A number of challenges have been identified and a systems engineering approach is described to address these challenges.