Distributed Real-Time Behavioral Requirements Modeling Using Extended UML/SPT

This paper introduces a reliable multicast transport protocol RCCMP (reliable congestion controlled multicast protocol) that has been designed to be simple, scalable, reliable and TCP-friendly. The congestion control is a central part of the protocol, where the feedback of the worst receiver is used to control a transmission window in a TCP-like fashion. The scalability issue is addressed with an exponential timers scheme, that is also used to estimate the number of receivers involved in the communication. The protocol neither needs support from network elements nor maintains state information dependent of the number of receivers. The paper presents a number of simulation results on its performance. Besides, some design choices are evaluated.

Reliable multicast is a technology used in a number of applications such as multi-receiver file transfer, streaming media, multimedia conferencing, collaborative processing etc. Pragmatic general multicast (PGM) is a reliable multicast transport protocol that runs over a best effort datagram service. Through this paper we propose an efficient loss recovery scheme for PGM. In our proposal a PGM router that receives a negative acknowledgement tries for local recovery prior to global recovery. The scheme works well when the sender/DLR is located further away from the PGM router than its receivers and the probability that a local receiver caches the packet is high. If there is a hit, the router retrieves the packet from its neighborhood, this results in a decrease in recovery latency, increase in throughput, reduction in power consumption also it alleviates the load at the sender/DLR.

Multicast Communications in Next-Generation Internet

This work presents new experimental results examining the loss tolerant unicast congestion control behavior of the NACK-Oriented Reliable Multicast (NORM) transport protocol documented initially as Internet Proposed Standard, Request for Comments (RFC) 5740. While RFC 5740 specifies a reliable multicast UDP-based transport protocol, NORM also has the ability to provide loss tolerant UDP unicast reliable transport that is well-suited for lossy wireless environments where protocols like TCP may not perform well. In addition, we introduce the design and use of a unicast SOCKS proxy for the NORM protocol called the NACK-Oriented Proxy (NORP) and validate the results of NORP performance against other NORM unicast experimental results. The availability of NORP will reduce the transition risk and improve the use of NORM unicast capabilities by not requiring end system application modifications. Our results examine a number of unicast congestion control variants of the NORM protocol, including an explicit congestion notification (ECN) mode, within an emulated lossy link modeled network environment. We include COTS hardware routing and radio-to-router interface (R2RI) within the test environment to examine and validate the use and performance of ECN-based packet marking and improved cross-layer flow control when available. The initial experiments demonstrate the significant advantage of using ECN-based assistance within error-prone wireless environments. We also show increased performance of an additional loss tolerant mode that does not require ECN infrastructure support. Coexistent transport fairness results show that NORM unicast modes are friendly to both inter-protocol flows (e.g., TCP flows coexisting) and to intra-protocol flows (e.g., Other NORM flows coexisting). We conclude by summarizing findings and discussing future work planned.

Object-oriented modeling has become the de-facto standard in the software development process during the last decades. A great deal of research in this area focuses on proposing modeling languages. In order to properly understand, and assess an object oriented modeling language, we believe that a set of criteria or requirements is needed. This paper presents a framework to investigate and compare graphical object oriented modeling languages. This framework is based on a requirement set for an ideal object-oriented modeling languages.

EOOLT 2010 was the third edition of the EOOLT workshop series. The workshop is intended to bring together researchers and practitioners from-different equation-based object-oriented (EOO) modeling language communities. This year's workshop also expands the scope to include the whole design space of languages for cyber-physical systems, where physical dynamics are mixed with networks and software. The workshop gathered 31 participants to present and discuss thirteen different papers grouped into the four areas of realtime oriented modeling languages and tools, modeling language design, simulation and model compilation, and modeling and simulation tools.

We analyze the maximum throughput that known classes of reliable multicast transport protocols can attain. A new taxonomy of reliable multicast transport protocols is introduced based on the premise that the mechanisms used to release data at the source after correct delivery should be decoupled from the mechanisms used to pace the transmission of data and to effect error recovery. Receiver-initiated protocols, which are based entirely on negative acknowledgments (NAKS) sent from the receivers to the sender, have been proposed to avoid the implosion of acknowledgements (ACKS) to the source. However, these protocols are shown to require infinite buffers in order to prevent deadlocks. Two other solutions to the ACK-implosion problem are tree-based protocols and ring-based protocols. The first organize the receivers in a tree and send ACKS along the tree; the latter send ACKS to the sender along a ring of receivers. These two classes of protocols are shown to operate correctly with finite buffers. It is shown that tree-based protocols constitute the most scalable class of all reliable multicast protocols proposed to date.

This paper introduces a XCP framework based reliable multicast transport protocol XRMCCP (XCP framework based Reliable Multicast Congestion controlled protocol) that has been designed to be simple, scalable and reliable for high bandwidth-delay product (BDP) networks. We observe that TCP Friendly Throughput Equation (TFTE), which many current multicast transport protocols use to estimate available rates of multicast sessions, has limits of performance in high BDP networks. XRMCCP generalizes XCP framework to support one-to-many transport congestion control. The scalability issue is addressed with an exponential timers scheme that is also used to estimate the number of receivers involved in the communication. The paper presents a number of simulation results on its performance. Besides, some design choices are evaluated.KeywordsCongestion ControlRound Trip TimeCongestion WindowFairness IndexBottleneck LinkThese keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

Pragmatic General Multicast (PGM) is a reliable multicast transport protocol for applications that require ordered or unordered, duplicate-free, multicast data delivery from multiple sources to multiple receivers. PGM guarantees that a receiver in the group either receives all data packets from transmissions and repairs, or is able to detect unrecoverable data packet loss. PGM is

Efficient and high-quality design of the substation automation systems has always been a real challenge. The problem of identification and location of information in the system and the description of information processing activities is a significant design problem. Information modeling is aimed at resolving it. An efficient approach to information modeling can significantly improve substation automation system development process. In this paper we propose the usage of the Unified Modeling Language (UML) as a main modeling language for expressing substation information models. UML was specified by Rational Software Corporation in 1997. Today, UML is adopted by the Object Management Group as an object-oriented modeling language with formally defined syntax and semantics. As expected, UML could be widely accepted in various industries (software, telecommunications, medicine, electro-industry, aero-industry etc.). The modeling approach is explained on one typical small-range 35 kV/10 kV distribution substation. Modeling steps: system usage specification, system structure specification, and behavior and constraints specification are described together with explanation of usage of some UML diagrams and modeling concepts.

In this paper we examine the impact of widely spread multicast groups on the performance of reliable multicast protocols. In a brief analysis we show that transmission cost for reliable multicast increases rapidly with the distance between retransmitting and receiving hosts. Since this distance is not considered by existing protocols, which are based on retransmissions originated at the sender or receiver, the performance often is rather poor and a new error recovery concept has to be developed. Our approach. the Scalable and Reliable Multicast Transport protocol (SRMT), allows retransmissions by extended multicast routers to limit the path length for error recovery. Moreover, the retransmission load can be further reduced by an XOR combination of packets. SRMT is defined as an overlay network model and therefore can be applied to any existing multicast protocol.

Regardless of the large number of Object-Oriented (OO) modeling languages currently being used in the Information Systems (IS) modeling process, unavailability of an OO modeling language that can be used in both the analysis and design phases disintegrates the two phases. The problem is, such disintegration can lead to a high level of missing information in the real world system from the analysis phase to the design phase. The approach of this study is to propose a framework to produce design phase models from analysis phase models using ontology based Unified Modeling Language (UML), thereby integrating the two phases. The results obtained from the porposed framework involve: a consructed language which can be used in generating the analysis phase scripts; and the development of script files based on the UML constructs at the analysis and design phases to automatically generate the UML scripts for those two phases. Since this study is a part of an ongoing research study, it can be concluded that, at the end of this study (1) both analysis and design phases would be able to integrate using a common OO modeling language (2) the manual work involved in the current analysis and design modeling would be reduced (3) the complexities and difficulties faced by the modelers (By modelers we mean the analysts and designers who are doing the analysis and design phase modeling) in using UML modeling tools would be reduced.

Problem statement: Multicasting communication network accepted a single message from an application and delivered copies of the message to multiple recipients at different locations. Recently, there has been an explosion of research literature on multicast communication environment. The objective of this study were to contribute the complexity of supporting current multicast applications, (i) the lack of reliable multicast transport mechanisms at the network level and (ii) the lack of network support for large scale multicast communication. The scaling problem of secure multicast key distribution compounded for the case where sender-specific keys need to be distributed to a group and required for sender-specific authentication of data traffic and minimize control overhead (iii) compare RC4, AES-128,RS(2) and RS(3) computation time of both algorithms. Approach: Algorithms were collected and performed computation time. In general the multicast key distribution scheme implemented for distributing 128 bit session keys. Thus the Maximum Distance Separable Codes (MDS Codes) needed for their encoding and decoding process. In rekeying scheme errors were occurred during over period of time or at a particular point of time and to eliminate all these errors in the level of encryption and decryption mechanism. The MDS codes played an important role in providing security services for multicast, such as traffic, integrity, authentication and confidentiality, is particularly problematic since it requires securely distributing a group (session) key to each of a group’s receivers. Results: First we showed that internet multicasting algorithms based on reverse path forwarding were inherently unreliable and present a source-tree-based reliable multicasting scheme also. The new scheme proposed and used as an inter-gateway protocol and worked on top of the previously developed distance vector and link state internet routing schemes. Next, to support large scale applications, we presented a scheme for partial multicasting and introduced a new network level operation, called gather. The partial multicasting mechanism allowed messages to be delivered to subsets of multicast destinations, while the gather operation aids gateways in selectively suppressing redundant messages, thus reducing the message complexity. Conclusion: Hence the findings suggested the control overhead reasonably minimized and using simulations, we investigated the efficiency of our schemes in supporting scalable application domain based multicast communication.

The Unified Modeling Language (UML) has been widely accepted as the standard object-oriented (OO) modeling language for modeling various aspects of software and information systems. The UML is an extensible language, in the sense that it provides mechanisms to introduce new elements for specific domains if necessary, such as web applications, database applications, business modeling, software development processes, data warehouses and so on. Furthermore, the latest work of the Object Management Group (OMG) on UML [1] resulted in a larger and more complicated specification, with even more diagrams for some good reasons. Although providing different diagrams for modeling specific parts of a software system, not all of them need to be applied in most cases. Therefore, heuristics, design guidelines, and lessons learned from experiences are extremely important for the effective use of UML and to avoid unnecessary complication.

\n Tree-based reliable multicast protocols are known to provide better\n scalability than the protocols based on pure sender- and\n receiver-initiated schemes. However, previous analytical work that\n has provided these results is based on a system model which assumes\n reliable control message delivery and synchronized local clocks.\n These assumptions are questionable simplifications, since they favor\n protocols using multicasted negative acknowledgments with NAK\n avoidance scheme. In this paper, we extend previous analysis by\n taking into account control data loss and asynchronous local clocks.\n\n We further analyze a new protocol class with particular importance,\n the tree-based approach with aggregated acknowledgments. In contrast\n to other approaches, this class provides reliability not only in\n case of message loss but also in case of node failures. Our results\n show that the additional overhead to cope with node failures is very\n low and therefore acceptable for reliable multicast implementations.\n