Reliable multicasting in the Xpress Transport Protocol

The Xpress Transport Protocol (XTP) is designed to meet the needs of distributed, real-time, and multimedia systems. This paper describes the genesis of recent improvements to XTP that provide mechanisms for reliable management of multicast groups, and gives details of the mechanisms used

Performance Model of Reliable Hybrid Multicast Protocol (RHMP)

The Pragmatic General multicast (PGM) and Elastic Reliable Multicast (ERM) are reliable multicast protocols. The difference between reliable and unreliable multicast protocol is that they make sure that the multicast data packets gets to its destinations. Both the PGM and ERM sends flood messages to the Rendezvous Point source (RPS) from the source node towards the stub nodes which then forward it to leaf nodes, leaf nodes that are not interested sends a prune message while any leaf node that misses a packet sends a message to the RPS through the stub node requesting for the multicast packet. A repair multicast packet is then forwarded to all leaf nodes that requested for it. In the reliable hybrid  multicast protocol (RHMP) being proposed the stub nodes originates the flood message to the leaf and uninterested leaf sends prune message, any stub that has one or more interested leaf sends a join message to the RPS. If a leaf node in the multicast distribution misses a multicast packet it requests a repair packet from its stub node and the stub node sends the repair data. A simulation model was developed to mimic the behaviour of PGM, ERM and RHMP in different network size using hierarchical network and the control bandwidth overhead (CBO) for each of the multicast protocols was calculated, the CBO was use as the cost metric. The result shows that the RHMP uses less CBO than PGM and ERM in a sparsely and densely populated network. For state storage it was discovered that the RHMP uses more resources at the stub nodes than at the source / RPS or leaf node when compared with PGM and ERM, but since the stub nodes are present in a distributed way it does not necessarily affect the multicast process

The STRESS Method for Boundary-point Performance Analysis of End-to-end Multicast Timer-Suppression Mechanisms

Evaluation of Internet protocols usually uses random scenarios or scenarios based on designers' intuition. Such approach may be useful for average-case analysis but does not cover boundary-point (worst or best-case) scenarios. To synthesize boundary-point scenarios a more systematic approach is needed.In this paper, we present a method for automatic synthesis of worst and best case scenarios for protocol boundary-point evaluation. Our method uses a fault-oriented test generation (FOTG) algorithm for searching the protocol and system state space to synthesize these scenarios. The algorithm is based on a global finite state machine (FSM) model. We extend the algorithm with timing semantics to handle end-to-end delays and address performance criteria. We introduce the notion of a virtual LAN to represent delays of the underlying multicast distribution tree. The algorithms used in our method utilize implicit backward search using branch and bound techniques and start from given target events. This aims to reduce the search complexity drastically. As a case study, we use our method to evaluate variants of the timer suppression mechanism, used in various multicast protocols, with respect to two performance criteria: overhead of response messages and response time. Simulation results for reliable multicast protocols show that our method provides a scalable way for synthesizing worst-case scenarios automatically. Results obtained using stress scenarios differ dramatically from those obtained through average-case analyses. We hope for our method to serve as a model for applying systematic scenario generation to other multicast protocols.Comment: 24 pages, 10 figures, IEEE/ACM Transactions on Networking (ToN) [To appear

Hastily Formed Networks (HFN) As an Enabler for the Emergency Response Community

The effects of natural or manmade disasters in communications infrastructures are so severe that immediately after the disaster the emergency responders are unable to use them. In addition, some areas do not have any useful infrastructure at all. To bridge this gap in communications, a need exists for a reliable technology not dependent on the existing infrastructure. This thesis focuses on first identifying the problem of communications gaps during natural or manmade disasters and reviewing the impact and potential benefit of implementing a solution based on the Hastily Formed Networks (HFN) model. The research explores the different technological solutions to solve this problem by evaluating documentation for commercial off-the-shelf technologies (COTS). Additionally, the thesis reviews the results of field experimentation conducted to evaluate the performance of these technologies in the field. The ultimate goal is to introduce the HFN concept as an enabler for the Emergency Response Community (ERC). Throughout this research, the focus revolves around testing COTS technologies. The research provides emergency responders with the background knowledge to make decisions on how to best bridge the gap of lack of communications under austere environments, and therefore enable them to provide better response.http://archive.org/details/hastilyformednet109456762Lieutenant Commander, United States Nav

Multicast Services for Multimedia Collaborative Applications

This work aims at providing multicast services for multimedia collaborative applications over large inter-networks such as the Internet. Multimedia collaborative applications are typically of small group size, slow group membership dynamics, and awareness of participants\u27 identities and locations. Moreover, they usually consist of several components such as audio, video, shared whiteboard, and single user application sharing engines that collectively help make the collaboration session successful. Each of these components has its demands from the communication layer that may differ from one component to another. This dissertation identifies the overall characteristics of multimedia collaborative applications and their individual components. It also determines the service requirements of the various components from the communication layer. Based on the analysis done in the thesis, new techniques of multicast services that are more suitable for multimedia collaborative applications are introduced. In particular, the focus will be on multicast address management and connection control, routing, congestion and flow control, and error control. First, we investigate multicast address management and connection control and provide a new technique for address management based on address space partitioning. Second, we study the problem of multicast routing and introduce a new approach that fits the real time nature of multimedia applications. Third, we explore the problem of congestion and flow control and introduce a new mechanism that takes into consideration the heterogeneity within the network and within the processing capabilities of the end systems. Last, we exploit the problem of error control and present a solution that supports various levels of error control to the different components within the collaboration session. We present analytic as well as simulation studies to evaluate our work, which show that our techniques outperform previous ones

An active protocol architecture for collaborative media distribution

Thesis (S.M.)--Massachusetts Institute of Technology, School of Architecture and Planning, Program in Media Arts and Sciences, 2002.Includes bibliographical references (p. 107-114).This thesis embarks on distributing the distribution for real-time media, by developing a decentralized programmable protocol architecture. The core of the architecture is an adaptive application-level protocol which allows collaborative multicasting of real-time streams. The protocol provides transparent semantics for loosely coupled multipoint interactions. It allows aggregation and interleaving of data fetched simultaneously from diverse machines and supports the location and coordination of named data among peer nodes without additional knowledge of network topology. The dynamic stream aggregation scheme employed by the protocol solves the problem of network asymmetry that plagues residential broadband networks. In addition, the stateless nature of the protocol allows for fast fail-over and adaptation to departure of source nodes from the network, mitigating the reliability problems of end-user machines. We present and evaluate the algorithms employed by our protocol architecture and propose an economic model that can be used in real-world applications of peer-to-peer media distribution. With the combination of an adaptive collaborative protocol core and a reasonable economic model, we deliver an architecture that enables flexible and scalable real-time media distribution in a completely decentralized, serverless fashion.by Dimitrios Christos Vyzovitis.S.M