This paper describes a new-generation open source tool for computer networking education called the Java Network Workbench 2 (JNW2), along with the successful teaching practices associated with that tool. JNW2 applies the constructivist educational philosophy, where students learn by doing, in this case by creating a software solution to an abstracted problem. The packaging of JNW2 is therefore different from production network simulators such as OPNET and ns3. The paper describes the philosophy and software design of JNW2 and relates these to the educational theory of constructivism. Experience and objective outcomes relating to teaching with JNW2 are described. Students are enthusiastic about using it and analysis shows a clear improvement in exam performance for concepts reinforced via JNW2 exercises.

This paper reports on combining emerging technologies for synchronous distance education in a student-implemented project. The goal is to realize, using latest web technologies, the MISTC open-source multimedia Internet client we developed earlier to support teaching in the classroom and online simultaneously. We summarize MISTC's capabilities, describe the development processes and tools utilized, and lessons learned.

Commercial software development today is dominated by the dramatic growth of Web/Internet-delivered information, combined with development techniques that feature rapid creation of reliable, maintainable application software. Staying current with these technologies is a constant challenge in any computer science curriculum. This paper reports on a pilot project course for six computer science fourth-year undergraduates that addressed this challenge in a synergistic way, to the benefit both of the participating students and of a government sponsor. The project created a new, open-source implementation of the Common Map API (CMAPI). It was accomplished using agile development techniques, intensive team activities, and advice from an industry CMAPI expert. Three one-month "sprints" resulted in a working, open-source system that met the needs of the sponsor and provided an excellent learning experience for all concerned. The approach used should be considered for inclusion in every undergraduate computer science curriculum.

This paper reports on progress in developing standardized methods for military coalitions to interoperate command and control (C2) systems and simulations as a system-of-systems, resulting in improved functionality and timeliness for participants. Command and control systems are networked software systems that commanders, staffs, and other participants use to exchange tasking information (called Orders) and status information for situational awareness (called Reports). Simulations are useful as C2 system elements for analysis and to stimulate training and mission rehearsal. C2SIM combines the two and has particular value in a coalition environment, where each nation prefers to use its own C2 system and simulation. The paper describes NATO and SISO activities in C2SIM, the technical approach used to achieve interoperability, and examples of its success.

The authors have supported online distance education delivery of the Master of Science in Computer Science degree at George Mason University for the past decade. We have focused on simultaneous online and classroom delivery, using an open-source hybrid approach combining synchronous classroom capture with the popular Moodle learning management system. Our program has been challenged to change its mode of operation to survive administration plans for growing asynchronous distance education in our institution. We report here on results of our efforts in rising to this challenge: technology enhancements to reduce support requirements and student surveys to understand the best new directions for the program.

In adding an online delivery option to an existing graduate program in computer science, important choices include (1) synchronous or asynchronous delivery and (2) for synchronous delivery, whether to deliver classroom and online teaching simultaneously. This paper describes the decisions made in adding an online option to an MSCS program, which now is maturing. The factors in favor of and against simultaneous delivery are discussed in detail and the conclusions reached for one particular program are described, including experience gained in the process and an open-source software system developed to support this form of delivery.

The Battle Management Language (BML) has been developed as an unambiguous representation of orders, reports and requests between military command and control (C2) systems and simulations. This paper describes development of two critical elements for BML experimentation. The first is a Web service that is used as a repository for the orders, reports, and requests, packaged as XML documents and stored in a relational database in a standard format. The second is a graphic user interface that supports inspection and modification of BML documents using forms that are created from the BML schemas at runtime, combined with a geospatial interface. This paper describes the role of these elements in C2-simulation interoperation and describes their architecture and features, as motivated by application in NATO Coalition BML experimentation. The software described is available as open source.

It is well understood that the two prevalent approaches to distance education, synchronous and asynchronous, can be combined to good effect. However, existing open source software generally is separated into these two categories. This paper introduces an open source capability that combines the popular Moodle asynchronous learning management system with a new synchronous online teaching/conferencing system called MIST/C. This combination is supporting online delivery of the Master's programs in our Computer Science Department effectively. This paper describes the design and implementation of MIST/C and our experience using it to support Computer Science MS programs.

Summary form only given. Recent developments in XML-based interoperation technology have shown how to achieve rapid integration of different systems that can be mapped into the same symbolic namespace. This talk will describe a project in this area that created a system of interoperating systems, consisting of six different national command and control systems and five national simulations from participating NATO nations, using the XML-based Battle Management Language (BML).

Real-time interoperation of command and control (C2) and simulation systems is a longstanding goal of the military distributed simulation community. The battle management language (BML) provides a capability for unambiguous communication that supports such a capability. The language is designed around a lexical grammar, conveyed by the extensible markup language (XML). Current implementations provide for asynchronous communication of military plans/orders and reports through a BML Web service (WS), which serves as a repository for BML messages. The Web service stores the elements of BML and their relationships using the joint command, control and consultation information exchange data model (JC3IEDM), which also serves as the basis for the BML vocabulary. This leads to a need to transform information without loss between the input/output language (BML) and the data storage model (JC3IEDM). This paper describes an innovative approach to implementing the BML WS, in the form of a script interpreter. The scripted approach has been proved to support rapid development of new services; also, its script representation offers a promising approach to documenting the transformation mappings in an emerging standard. The paper explains the current state of BML and the rationale for the interpreted BML WS. It also describes the features of the scripting language and some successful uses of the approach. The paper closes with a description of our most recent development: a scripted BML WS with publish-subscribe capabilities.

Previous ITiCSE papers have reported on Network EducationWare (NEW), an open source software system that supports synchronous and asynchronous distance education easily and inexpensively via the Internet. This paper reports on an innovative capability recently added to NEW that enables simultaneous execution of applications on all participating computers in both Windows and Linux systems, and explains how we have used this capability to teach a course in Computer Graphics online. Teaching graphics in this way previously was impossible because transmitting the visual output of graphics programs in real time with good quality is too demanding for normal Internet connections. This problem was solved by using the NEW application launcher to invoke Java classes, provided by the instructor, on all student computers simultaneously. The capability works with modest Internet capacity and also is captured in recorded sessions for asynchronous use. We explain how the NEW capability works and describe its use in online teaching of Computer Graphics.

The joint battle management language (JBML) project is at the forefront of the current interest in supporting development of distributed systems with simulation elements by means of Web services. This paper reports on work to develop an extensible capability to serve as a basis to expand JBML coherently, in multiple domains of warfare simulation (land, air, and maritime). The project has created a schema for a Web service that serves as the external interface for orders being pushed into the Web service by the different military components' domain-unique command and control (C2) systems, and pulled from the service by different simulations that function as a cooperating system. The Web service consists of multiple, re-usable layers in an open source implementation that is intended to serve as a basis for an expanding open standards development effort for the coalition battle management language. We report on the approach used to design and develop the schema and supporting Web service based on a lexical grammar, and the results when three C2 systems and two simulation systems were combined, using the Web service as its core.

Network EducationWare (NEW) is a powerful and robust open-source multimedia system for synchronous Internet distance education. It supports blended presentations in a form we call simulteaching, where some students are in a traditional classroom and others participate in real time over the Internet. It also records the class as presented, so that students can attend class delayed in time. NEW has been designed to be highly modular and to make effective use of both network bandwidth and human time. Reference [1] describes how George Mason University has used NEW to offer a popular and innovative MS degree in Computer Science, at low cost.

Abstract We present a new post processing method of simulating depth of field based on accurate calculations of circles of confusion. Compared to previous work, our method derives actual scene depth information directly from the existing depth buffer, requires no specialized rendering passes, and allows easy integration into existing rendering applications. Our implementation uses an adaptive, two‐pass filter, producing a high quality depth of field effect that can be executed entirely on the GPU, taking advantage of the parallelism of modern graphics cards and permitting real time performance when applied to large numbers of pixels.

This paper addresses issues in interconnecting military command and control (C2) and simulation systems, using Web technologies and mediation via a common representation, the command and control information exchange data model (C2IEDM). The authors supported a NATO Exploratory Team that designed an experimental program to assess the approach and prepare for its use by coalitions. As part of that activity, the United States and France implemented an international demonstration of C2 and simulation systems interoperating using Web services and C2IEDM. This paper reports on how C2 and simulation systems were employed with Web technologies to achieve a successful demonstration in a very short time period, including experience gained in the process and plans for future development of C-BML capabilities

Understanding the characteristics of information flow in large scale real-time distributed virtual simulations (RT-DVS) is important for the development of network services that are able to meet the robust needs of this simulation environment. Being able to quantify these characteristics enables network performance estimations to support the growing demand for use of Internet/Web-based services in large scale RT-DVS applications and interest in simulation interoperability with communications, computers, intelligence, surveillance, and reconnaissance (C4ISR) systems. This simulation environment requires open network communications protocols that can accommodate the efficient distribution of large amounts of data to many users, which in turn implies the use of many-to-many multicast network services that are not readily available as an open Internet service today. This paper describes results from the study of network information flow in three simulation experiments and presents a supporting analytical model for use in predicting performance of an early implementation of the extensible modeling and simulation framework overlay multicast protocol (XOM). XOM is designed to support many-to-many multicast for efficient exchange of real-time information among many users in real-time simulations over the Internet. We summarize the architecture and key design considerations of XOM that result from these live simulations studies and our measurements of network traffic and the resulting analytical model.

Summary form only given. The grid, or grid computing, provides a new and unrivalled technology for large scale distributed simulation as it enables collaboration and the use of distributed computing resources. Last year at DS-RT 2004 a panel was convened to consider the impact of the grid on distributed simulation. Four members presented their views of this area and together they tried to identify the main research issues involved in applying grid technology to distributed simulation and the key future challenges that need to be solved to achieve this goal. These challenges included not only technical ones, but also social ones such as management methodology and the development of standards. This year we revisit this fast changing technology and ask the questions: 1) What major changes has grid computing had over the past year?; 2) How can distributed simulation and related applications benefit from grid computing?; 3) What are the barriers to this?; 4) Are there alternative new technologies that would be a better ROI for distributed simulation than grid computing?.

The extensible battle management language project has implemented XML based data mediation services to translate from legacy XML schemas into XML schemas, based on a common tag set generated from the command and control information exchange data model (C2IEDM). The C2IEDM was developed by NATO to enable interoperation among operational command and control (C2) systems of coalition forces. XBML's ability to exchange simulation information based on C2IEDM enables a major expansion in interoperability, in that C2 systems now can be coupled with modeling and simulation software. The benefit of our specific data mediation approach is that legacy systems are required only to provide information exchange interfaces based on XML, as the adaptation of such systems is done by configuring the layers of the recommended architecture. We present the architecture and operational principles used to achieve interoperation in this way.

Growing demand for use of Internet/Web-based services in real-time distributed virtual simulation (RT-DVS) and other real-time applications is fueling extensive interest in overlay multicast protocols. These applications demand Quality of Service (QoS) and many-to-many multicast services that are not available in underlying Internet services today. This paper describes an early implementation of an overlay multicast protocol designed to support many-to-many multicast for RT-DVS applications called Extensible Modeling and Simulation Framework Overlay Multicast (XOM). We first describe the architecture and key design considerations of XOM. We then provide preliminary results from lab experiments with our prototype. Our results indicate that we can achieve performance objectives for support of web-based services for RT-DVS.

The Experimentation Command and Control Interface (XC2I) project has developed an architecture for a Web-service based viewer/controller for use with distributed simulations supporting military experiments. As part of this activity, a capability for Interest Management with three functions is being created. The functions are Role-Based Access Control (RBAC), Area of Interest Management (AOIM), and Aggregation Interest Management (AGIM). While the approach is compatible with High Level Architecture (HLA) for Modeling and Simulation, primary information exchange takes place using the Web services, i.e. software-to-software messaging interfaces that operate over Web protocols such as XML/SOAP. This paper presents a Web Services Internet Management (WSIM) architecture designed to achieve these capabilities in a way that is compatible with simulations using the HLA. The protocols and information flow structure are described, along with the architecture's design rationale, interest management rules, and plans for its implementation. The paper concludes with a description of potential for future development of WSIM, including adoption of the Command and Control Information Exchange Data Model (C2IEDM) and use of Overlay Multicast for data distribution.

The Grid provides a new and unrivaled technology for large scale distributed simulation as it enables collaboration and the use of distributed computing resources. This panel paper presents the views of four researchers in the area of Distributed Simulation and the Grid. Together we try to identify the main research issues involved in applying Grid technology to distributed simulation and the key future challenges that need to be solved to achieve this goal. Such challenges include not only technical challenges, but also political ones such as management methodology for the Grid and the development of standards. The benefits of the Grid to end-user simulation modelers also are discussed.

Many-to-many multicast transmission is an essential network capability for scalable distributed simulation. The many open issues that make network-layer multicast impractical over the Internet today are likely to continue to be insurmountable and to prevent deployment in a manner that will meet the quality of service (QoS) and many-to-many multicast needs of real-time distributed virtual simulation (RT-DVS). We propose an alternative approach, whereby the IP multicast function is relocated to the simulation host computer and also used to provide for QoS enabled services on a priority basis. This paper explores the concept of such a host-based multicast system with QoS and its suitability for RT-DVS. The paper defines the basic requirements of a host-based multicast protocol to support RT-DVS and proposes a quantitative model for evaluation of system alternatives.

Continued research into distributed agent-based systems and evolving Web based technologies are opening up tremendous possibilities for the deployment of large scale and highly extensible and flexible simulation systems. However, the question remains as to how well agent and Web based simulation systems can use underlying network services. This is especially true for complex distributed simulations that have multiple participants and real-time data delivery requirements. This paper addresses the issue of interconnection patterns among Web-based simulation agents. We first describe a simple agent-oriented architectural extension to an existing distributed simulation system. Next, we present a set of interconnection algorithms between the agents in the system, under the assumption that only end-host multicast is available. We experimentally evaluate our approach under a number of different scenarios. Our results show that by using a proper connection strategy it is possible to get performance comparable to network-layer multicast for agent-based systems that use end-host multicast.

Denial-of-service (DoS) attacks have received a great amount of attention in research communities and general public alike, due to recent, high-profile attacks against major Internet e-commerce sites. We present a countermeasure against such attacks, called the congestion-triggered packet sampling/packet filtering (CTPS/PF) architecture. With CTPS/PF, a packet sampling mechanism that is integrated with the congestion control mechanism at routers is used to detect DoS attacks, and packet filters are activated only when sampling results warrant action. One important concern in deploying any form of traffic analysis in the critical data-forwarding paths of the Internet is performance. Our sample processing algorithm takes into account the confidence indicators of statistic results to raise alarms with relatively small numbers of samples. Moreover, the per-sample processing complexity is only O(1). Our simulation study reveals that the CTPS/PF architecture is able to detect the presence of DoS attacks and take proper action within hundreds of milliseconds to tens of seconds. Moreover, the average sampling overhead during a congestion period is in the vicinity of 1 sample per second.

Network-based distributed education is a reality today. At George Mason University, we have been pursuing a capability beyond the widespread practice of supporting courses with webpages: delivering lectures and seminars in real time, over the Internet. This paper describes the range of distributed education technologies available today, focusing on issues of instructor presentation, student participation, and temporal qualities of response to student questions. The analysis supports our selection of desktop audiographics for synchronous Internet-based course delivery. Courses that have been presented in this mode are described, along with factors influencing their success and factors in student participation.

For wide-area networking of distributed interactive simulation (DIS) a real-time, resource-reserving, multicast network with appropriate encryption is required. Latency and data volume requirements are described. Standards for DIS communications and their impact on network traffic are explained. Evolutionary history is traced for the current network serving these needs, the Defense Simulation Internet. The most likely path for future expansion of DIS networking uses emerging commercial technologies such as asynchronous transfer mode (ATM) and Internet protocol multicast (IPmc) with resource reservation. The architecture and issues for an ATM network meeting future DIS requirements is described; areas of active research such as compression and multicast grouping are explained.>