Abstract-One of the most widely used architectures for packet switches is the crossbar. A special version of a it is the buffered crossbar, where small buffers are associated with the crosspoints. The advantages of this organization, when compared to the unbuffered architecture, is that it needs much simpler and slower scheduling circuits, while it can shape the switched traffic according to a given set of Quality of Service (QoS) criteria in a more efficient way. Furthermore, by supporting variable length packets throughout a buffered crossbar: a) there is no need for segmentation and reassembly circuits, b) no internal speedup is necessary, and c) synchronization between the input and output clock domains is simplified. In this paper we present an architecture, a hardware implementation analysis, and a performance evaluation of such a buffered crossbar. The proposed organization is simple, yet powerful and can be easily implemented using today's technologies. Our evaluation shows that it outperforms most of the existing packet switch architectures, while its hardware cost is kept to a minimum.

Case studies for evaluating tools in security testing are powerful. Although they cannot achieve the scientific rigor of formal experiments, the results can provide sufficient information to help professionals judge if a specific technology being evaluated will benefit their organization. This paper reports on a case study done for evaluating and revisiting a recently introduced combinatorial testing methodology used for web application security purposes. It further reports on undertaken practical experiments thus strengthening the applicability of combinatorial testing to web application security testing.

The number of potential security threats rises with the increasing number of web applications, which cause tremendous financial and existential implications for developers and users as well. The biggest challenge for security testing is to specify and implement ways in order to detect potential vulnerabilities of the developed system in a never ending quest against new security threats but also to cover already known ones so that a program is suited against typical attack vectors. For these purposes many approaches have been developed in the area of model-based security testing in order to come up with solutions for real-world application problems. These approaches provide theoretical background as well as practical solutions for certain security issues. In this paper, we partially rely on previous work but focus on the representation of attack patterns using UML state diagrams. We extend previous work in combining the attack pattern models with combinatorial testing in order to provide concrete test input, which is submitted to the system under test. With combinatorial testing we capture different combinations of inputs and thus increasing the likelihood to find weaknesses in the implementation under test that can be exploited. Besides the foundations of our approach we further report on first experiments that indicate its practical use.

Security testing of web applications remains a major problem of software engineering. In order to reveal vulnerabilities, manual and automatic testing approaches use different strategies for detection of certain kinds of inputs that might lead to a security breach. In this paper we compared a state-of-the-art manual testing tool with an automated one that is based on model-based testing. The first tool requires user input from the tester whereas the second one reduces the necessary amount of manual manipulation. Both approaches depend on the corresponding test case generation technique and its produced inputs are executed against the system under test (SUT). For this case we enhance a novel technique, which combines a combinatorial testing technique for input generation and a model-based technique for test execution. In this work the input parameter modelling is improved by adding constraints to generate more comprehensive and sophisticated testing inputs. The evaluated results indicate that both techniques succeed in detecting security leaks in web applications with different results, depending on the background logic of the testing approach. Last but not least, we claim that attack pattern-based combinatorial testing with constraints can be an alternative method for web application security testing, especially when we compare our method to other test generation techniques like fuzz testing.

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