Joseph Macker

In this paper we present a generic environment for creating message-oriented server-side proxies to support adaptation from TCP transport-oriented client-server sessions to many-to-many peer-to-peer networking environments more suitable for deployment in dynamic wireless networks, capable of multicast forwarding. At its input, GUMP provides an interface for exposing network server implementations in order to allow existing GUI applications to connect to GUMP. At the back-end, GUMP's generic service discovery and multicast interfaces allow access to multiple implementations, enabling the discovery of necessary services on the network, maintenance of the network state, and transport of messages amongst peers, for tuning to a specific network environment. At the heart of GUMP, there is a mechanism for selecting a server-side proxy implementation for a given messaging protocol, allowing multiple proxies to co-exist and run time adaption of the system. As a primary example and use case, we show how GUMP has been used to implement an XMPP proxy allowing existing off-the-shelf XMPP client software to dynamically create and operate multi-user chat sessions in a serverless network environment. This resulting proxy integration demonstrates the power of GUMP in its ability to adapt between different methods of input using either HTTP or TCP oriented server systems, the use of its different discovery subsystem bindings (SLPv2 and JmDNS), and its support for multicast architectures. GUMP therefore allows a single messaging protocol server-side implementation to be dynamically adapted to suit a particular distributed wireless deployment environment at run time.

The design and development of a digital signal processor (DSP) based groundwave and ionospheric communication channel simulator is described. The primary objective is to simulate communication channel perturbations for a network of communication via an array of DSP modules operating in real-time. This array of channel simulator processors is a subsystem of the multimode tactical network simulator (TACNETSIM) being developed by the Information Technology Division at the Naval Research Laboratory (NRL). The propagation model developed is based upon intra-battlegroup high frequency (HF) communications. The communication channel model consists of two modes of propagation: HF groundwave and HF skywave. The HF skywave component is simulated via a Watterson ionospheric model. The real-time DSP implementation of the Watterson ionospheric model is described in terms of subprocesses. The performance of each subprocess is shown to be within established statistical parameters. Detailed specifications are given of both the hardware and software design. The simulator is designed for dynamic channel modeling and includes a data interface for real-time program control.

This work describes an analysis of applying different election heuristics to connected dominated set (CDS) algorithms within different topological graph taxonomies. Our initial motivation for this study was a general observation that a significant amount of research in mobile ad hoc network (MANET) algorithm design and related election heuristic evaluation is based upon geometric random or other types of uniform random network models. Our hypothesis is that small world or scale-free network topology analysis can result in significantly different design feedback that may be suppressed by exclusive use of uniform random analysis. Previous research has shown that power law based networks more accurately represent types of real world and social networks and we believe it is important to understand the potential tradeoffs in distributed algorithm design for self-organizing networks beyond traditional random network models. We provide a concrete example by applying the existing specification for the essential-CDS algorithm used within the mobile ad hoc network (MANET) Simplified Multicast Forwarding (SMF) and the OSPF Extensions for MANET MDR approach. We model random, small world, and power law based network types based upon well known models. We demonstrate that the network graph taxonomy used in modeling affects the design analysis such as understanding the resulting effectiveness of various distributed election heuristics. Future work is planned to extend these initial results to more dynamic analysis.

Service-based discovery mechanisms for dynamic mobile ad-hoc and mesh networks require additional robustness and performance features beyond present practices. However, leveraging existing standards and application service interfaces where possible will aid in wider deployment. To achieve the latter, supporting standardized protocols is desirable, but present approaches focus on fixed Internet use and do not provide solutions suitable for self-organizing wireless architectures. We have previously reported on the merits of different profiles (proactive, reactive and opportunistic caching), the use of limited multi-hop multicast, and information exchange reduction to improve service discovery in wireless ad hoc environments, using our Independent Network Discovery Interface (INDI) discovery system. In this paper, we describe the integration of INDI functionality with an already widely deployed localized service discovery method, multicast DNS (mDNS). We show resulting INDI interoperability with mDNS and compare and contrast the underlying approaches, through the use of networking tools, to provide empirical evidence illustrating the advantages of INDI-mDNS, when applied in a MANET context.

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.

Abstract Existing relay set election algorithms used for self-organizing mobile ad hoc network (MANET)[1] routing control and data forwarding are often designed to continuously minimize the relay set at topological snapshots in time. Due to errors in wireless link ...

In this paper we discuss the adaptation of TCP transport-oriented client–server messaging protocols to many-to-many peer-to-peer networking environments more suitable for deployment in dynamic wireless networks capable of multicast forwarding. We describe four main issues in adapting such protocols: exposing a network server for receiving TCP session data; the creation of server-side semantic proxies to process the messages and adapt to a serverless environment; service discovery to enable the discovery of necessary services on the network and to maintain the network state; and finally support for multicast interfaces for the transportation of messages amongst peers. We show that our system, called GUMP, can be used to support such protocol adaptations and to illustrate we use GUMP to implement an XMPP proxy allowing existing off-the-shelf XMPP client software to dynamically create and operate multi-user chat sessions in a serverless network environment. We then present two sets of results that show how appropriate discovery systems and transport protocols can dramatically increase the success of protocols, such as XMPP, within a mobile wireless networked environment. Specifically, we first demonstrate that a GUMP supported discovery system, INDI, can significantly increase the success rates and decrease latency of discovering services through profiles, caching and retrying schemes. Second, we show that success rates for XMPP transmission of messages can be vastly improved through the use of multicast as apposed to TCP within the mobile environment. These two factors provide strong empirical support for the justification of GUMP in its ability to adapt between a client–server and serverless world.

This paper presents empirical analysis of serverless, multi-user chat in multicast-capable tactical environments. The implemented group communications middleware is based on serverless XMPP messaging. We compare the effectiveness and performance of serverless messaging over multicast, as well as typical client server TCP messaging. The experiments are performed using the Common Open Research Emulator in conjunction with the Extendable Mobile Ad-Hoc Network Emulator, to provide a higher-fidelity emulation than previous work.

This work discusses the adaptation of group-oriented messaging and chat technology for operation in serverless, multicast-capable mobile wireless architectures. The main goals are to allow group messaging and chat sessions to fragment/coalesce, operate through disrupted TCP conditions, and improve bandwidth utilization when multicast is available. In addition, the solution demonstrates proxying and gateway methods to interoperate with existing client and server standards and software. The approach presents several innovations that extend and adapt extensible Messaging and Presence Protocol (XMPP) standards for incorporating group serverless chat and messaging within more challenging operational environments. While there is large body of work on messaging middleware solutions, this paper concentrates on the adaptation of specific XMPP standards for serverless, multicast operation. We discuss our working implementation prototype and present initial experimentation comparing client/server multi-user chat (MUC) operation to serverless multicast MUC within several mobile network scenarios. In addition, we demonstrate a gatewaying solution for serverless MUC systems to interoperate with conventional MUC server-based systems. The specific test scenarios are instrumented to operate within a wireless mobile emulation environment using mobile ad hoc network (MANET) unicast and multicast routing technology. This approach remains independent of any particular routing algorithm and the proxied XMPP protocol module allows for the deployment of existing real-world client software across all nodes of the network. The initial findings show the significant performance potential for serverless MUC extensions. In addition to these results, we discuss some ongoing design challenges and future planned work.

Most applications and network protocols are designed under the assumption of a stable and consistent physical network infrastructure. However, the communications infrastructures of most military tactical networks are dynamic and dependent on mission CONOPS and network topology. Further, they are highly variable in their capabilities from one data link to the next. Consequently, it is difficult for standard applications and services to maintain reliable quality of service when transiting to a dynamic tactical network, or crossing the borders between different classes of military networks. Ultimately, this lack of network awareness impacts the quality and timeliness of actionable intelligence delivered to the warfighter. General Dynamics and the Naval Research Laboratory (NRL) have collaborated on efforts to improve the reliable delivery of live video data across these disadvantaged tactical networks. We address the development of a network-aware video server, which senses network characteristics and dynamically transcodes video to meet the capacity of network between the server and clients. End-to-end network characteristics are required to drive the video transcoder. These network attributes can either be derived from software methods by analyzing the network protocol, or using specialized network hardware (e.g. tactical radios, routers, or QoS devices). For this effort end-to-end network awareness was collected from the NACKOriented Reliable Multicast (NORM) [1] protocol operation. Hooks in the NORM protocol provide a network information service with access to path bandwidth, delay, and lost packets. The video server uses the network information service to adapt the video by adjusting frame size, frame rate, and compression according to current network conditions to deliver the video with minimal delay. A comparison of how video is streamed over enterprise networks and the improved delivery methods made by General Dynamics and NRL for tactical networks is presente- .

... Keith Scott, Tamer Refaei, Nirav Trivedi, Jenny Trinh Communications Network Engineering & Analysis Dept. ... scenario in which nodes in a low bandwidth loosely-connected ad-hoc network periodically send position/location information (PLI) messages to a shore base station. ...

QUITE simply, the terminology of “wireless ad hoc net-work” refers to a multihop wireless network that lacks an infrastructure. Unlike cellular wireless networks, there are no base stations and there is no distinction between uplink and downlink channels. Instead, communication is implemented on a peer-to-peer basis, necessitating the use of relaying. 1 Although the primary applications of wireless ad hoc networks have thus far been military in nature, they are also well suited to disaster recovery support and to commercial ...

Abstract: This document describes the messages and procedures of the Negative-acknowledgment (NACK) OrientedReliable Multicast (NORM) protocol. This protocol is designed to provide end-to-end reliable transport ofbulk data objects or streams over generic IP multicast routing and forwarding services. NORM uses aselective, negative acknowledgment mechanism for transport reliability and offers additional protocolmechanisms to allow for operation with minimal "a priori" coordination among senders and...

Natural, technological and man-made disasters are typically followed by chaos that results from an inadequate overall response. Three separate levels of coordination are addressed in the mitigation and preparedness phase of disaster management where environmental conditions are slowly changing: (1) communication and transportation infrastructure, (2) monitoring and assessment tools, (3) collaborative tools and services for information sharing. However, the nature of emergencies is to be unpredictable. Toward that end, a fourth level of coordination – distributed resource/role allocation algorithms of first responders, mobile workers, aid supplies and victims – addresses the dynamic environmental conditions of the response phase during an emergency. A tiered peer-to-peer system architecture could combine those different levels of coordination to address the changing needs of disaster management. We describe in this paper the architecture of such a tiered peer-to-peer agent-based coordination decision support system for disaster management and response and the applicable coordination algorithms including ATF, a novel, self-organized algorithm for adaptive team formation.

This document discusses the creation of reliable multicast protocols utilizing negative-acknowledgment (NACK) feedback. The rationale for protocol design goals and assumptions are presented. Technical challenges for NACK-based (and in some cases general) reliable multicast protocol operation are identified. These goals and challenges are resolved into a set of functional "building blocks" that address different aspects of reliable multicast protocol operation. It is anticipated that these building blocks will be useful in generating different instantiations of reliable multicast protocols.

A number of technologies are evolving that will help formulate more adaptive and robust network architectures intended to operate in dynamic, mobile environments. One technology area, mobile ad hoc networking (MANET) enables self-organizing, multi-hop heterogeneous network routing services and organization. Such technology is important in future DoD networking, especially in the forward edge of the battlespace where self-organizing, robust networking is needed. A second technology area, multi-agent systems (MAS) can enable autonomous, team-based problem solving under varying environmental conditions. Previous work done in MAS has assumed relatively benign wired network behavior and inter-agent communications characteristics that may not be well supported in MANET environments. In addition, the resource costs associated with performing inter-agent communications have a more profound impact in a mobile wireless environment. The combined operation of these technology areas, including cross-layer design considerations, has largely been unexplored to date. This paper describes ongoing research to improve the ability of these technologies to work in concert. An outline of various design and system architecture issues is first presented. We then describe models, agent systems, MANET protocols, and additional components that are being applied in our research. We present an analysis method to measure agent effectiveness and early evaluations of working prototypes within MANET environments. We conclude by outlining some open issues and areas of further work

This document describes the messages and procedures of the Negative-ACKnowledgment (NACK) Oriented Reliable Multicast (NORM) Protocol. This protocol can provide end-to-end reliable transport of bulk data objects 1 http://trustee.ietf.org/license-info

... there is rarely a direct incentive to tradeoff network-wide system improvements --representing the ... and resource constraints of wireless networks intensify the need for system efficiency, while the ... the design of the sensor network is optimized for low energy consumption using non ...