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Cooperative work in learning environments has been shown to be a successful extension to traditional learning systems due to the great impact of cooperation on students' motivation and learning success. A recent evaluation study has confirmed our hypothesis that students who constructed their roles in a cryptographic protocol cooperatively as sequence of actions in a user interface were faster in finding a correct solution than students who worked on their own. Here, students of a cooperation group modeled a user interface collaboratively for simulation of a cryptographic protocol using interactive modeling tools on a shared touch screen. In this paper, we describe an extended approach to cooperative construction of cryptographic protocols. Using a formal language for modeling and reconfiguring user interfaces, students describe a protocol step-by-step, modeling subsequent situations and thereby actions of the protocol. The system automatically generates a colored Petri net, which is matched against an existing action logic specifying the protocol, thus allowing formal validation of the construction process. The formal approach to modeling of user interfaces covers a much broader field than a simple cryptographic protocol simulation. Still, this paper seeks at investigating the use of such a formal modeling approach in the context of cooperative learning of cryptographic protocols and to develop a basis for more complex learning scenarios. [ABSTRACT FROM AUTHOR]

Distributed coordination function (DCF) is a primary random access mechanism of IEEE 802.11, which is the basic protocol of wireless LAN based on the CSMA/CA protocol. It enables fast installation with minimal management and maintenance costs and is a very robust protocol for the best effort service in wireless medium. The current DCF, however, is known to be unsuitable for real-time applications such as voice message transmission. In this paper, we focus on the performance issues of IEEE 802.11 which accommodates the prioritized messages. Existing results use the initial window size and backoff window-increasing factor as tools to handle the priority of the messages. Instead, we introduce a novel scheme which chooses the backoff timer with arbitrary probabilities. By this, one can greatly reduce the backoff delay of the lower priority messages without degrading the performance of higher priority. Additionally, we provide a step-by-step procedure which determines the system parameters such as the initial window size, backoff window-increasing factor, and the backoff timer choosing probabilities, guaranteeing the quality of service (QoS). [ABSTRACT FROM AUTHOR]

Businesses are faced today with the challenge of leveraging existing network infrastructures while evolving to technologies that will provide a positive impact on their business performance. Internet Protocol (IP) is a technology foundation that many companies have begun to leverage, but IP requires a more integrated strategy for seamless migration and the achievement of its full benefits. In this paper, we examine the creation of an Enterprise IP Strategy from a business impact and a technology point of view and provide factors to consider when developing this strategy. A framework considering business perspective and technology umbrella is presented to guide businesses to make the right choice for networking needs. IP is a common thread that runs through various systems and networks comprising enterprise IT infrastructure. In the last five years, virtually everyone from shipping clerks to CEOs has been touched by IP's influence. Hence, IP provides a strategic vantage point for building a sound enterprise networking strategy. [ABSTRACT FROM AUTHOR]

In a distributed system, it is often necessary for nodes to agree on a particular event or to coordinate their activities. Applications of distributed agreement are many, such as Commit Protocols in distributed database systems, selection of a monitor node in a distributed system, detecting an intruder, or agreeing on the malicious behavior of a node. Among many forms of Distributed Agreement, one form is called Approximate Agreement (AA), in which the nodes, by exchanging their local values with other nodes, need to agree on values which are approximately equal to each other. Research on AA for fully connected networks is relatively mature. In contrast, the study of AA in partially connected networks has been very limited. More specifically, no general solution to the AA problem exists for such networks. This research solves the AA problem for a specific, scalable, partially connected network with limited relays. The research considers the worst failure mode of nodes, called Byzantine, and hybrid failure modes. The results show low communication cost in comparison to fully connected networks. The network is designed to take advantage of the results available for fully connected networks. Thus, the analysis for obtaining the expressions for Convergence Rate and Fault Tolerance becomes relatively easy. [ABSTRACT FROM AUTHOR]