For many distributed applications, the PublishSubscribe communication model emerges as a viable alternative to the Request-Reply model. It provides a strong decoupling among participants, simplify the reutilization of components and the non-stop reconfiguration of applications. Unfortunately, this strong decoupling also makes it hard to support Quality of Service (QoS) parameters, like bandwidth and latency, in an efficient manner.

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In this paper, we propose a simple practical scheme for many-to-many IP multicasting. The proposed scheme is based on the core based tree (CBT) protocol, and designed to enhance the CBT in the viewpoints of tree cost and traffic concentration. In the scheme, each group user is simply connected to the nearest core router in the network. Each core router forwards the source traffic to networks via the pre-configured backbone core trees spanning all the core routers in the network. To ensure that the backbone core tree keeps only the core routers with active group users, the core routers that have no downstream users are removed from backbone core tree. By experiments, we see that the proposed scheme significantly improves the existing CBT scheme in terms of tree cost and traffic concentration.

Abstract—Computer supported collaborative applications on overlay networks are gaining popularity among users who are geographically dispersed. Examples of these kinds of applications include video-conferencing, distributed database replication, and online games. This type of application requires a multicasting subnetwork, using which messages should arrive at the destinations within a specified delay bound. These applications also require that destinations receive the message from the source at approximately the same time. The problem of finding a multicasting subnetwork with delay and delay-variation bound has been proved to be an NP Complete problem in the literature and heuristics have been proposed for this problem. In this paper, we provide an efficient heuristic to obtain a multicast subnetwork on an overlay network, given a source and a set of destinations that is within a specified maximum delay and a specified maximum variation in the delays from a source to the destinations. The time-complexity of our algorithm is OðjEjþnk logðjEj=nÞþm 2 kÞ, where n and jEj are the number of nodes and edges in the network, respectively, k is the number of shortest paths determined, and m is the number of destinations. We have shown that our algorithm is significantly better in terms of time-complexity than existing algorithms for the same problem. Our extensive empirical studies indicate that our heuristic uses significantly less runtime in comparison with the best-known heuristics while achieving the tightest delay variation for a given end-toend delay bound. Index Terms—Multicasting protocols, overlay networks, shortest path. 1

Multicast routing allows network sources to use network resources efficiently by sending only a single copy of data to all group members. In the delay constrained group multicast routing problem (DCGMRP), every group member is also a source, and has an individual minimal delay and bandwidth requirement. The routing algorithm must, for each member of the group, construct a source-based routing tree spanning all the other member nodes without exceeding the capacities of the traversed links, while satisfying the stated delay constraints. Previous work adopted the direct, intuitive approach by first creating a source-based multicast tree independently for each member node, and then iteratively locating network links whose capacity constraint are violated and eliminating the violation by rerouting the trees. In this paper, we investigate a number of efficient and effective algorithms, DCGM IA þ; DCGM GR and DCGM CP; for solving DCGMRP and compare their performance with previous proposals. Through extensive experiments, our proposals are shown to outperform previous algorithms in constructing group multicast trees with low costs and high success ratios.

Abstract. The rapid evolution of real-time multimedia applications requires Quality of Service (QoS) based multicast routing in underlying computer networks. The constrained Steiner Tree, as the underpinning mathematical structure, is a well-known NP-complete problem. In this paper we investigate a variable neighborhood descent (VND) search, a variant of variable neighborhood search, for the delay-constrained leastcost (DCLC) multicast routing problem. The neighborhood structures designed in the VND approaches are based on the idea of path replacement in trees. They are simple, yet effective operators, enabling a flexible search over the solution space of this complex problem with multiple constraints. A large number of simulations demonstrate that our algorithm is highly efficient in solving the DCLC multicast routing problem in terms of the tree cost and execution time. To our knowledge, this is the first study of VND algorithm on the DCLC multicast routing problem. It outperforms other existing algorithms over a range of problem instances. 1

Abstract: Active and programmable networks change the functionality of routers and switches by using VPN endpoints and active packets. The authors present a new packet scheduling scheme called active scheduling to control and maintain QoS parameters in virtual private networks (VPNs) within the confines of adaptive and programmable networks. In active scheduling a VPN endpoint on the router monitors the accumulated queuing delay for each service. To control and to keep the end-to-end delay within the bounds, the delays of the packet transmitted are adjusted dynamically by VPN endpoints on the routers spanning the VPN. If there is an increase or decrease in delay of packets, VPN endpoints on a source node informs the destination node to adjust the delay of the packets. This keeps the end-to-end delay of services within the specified bounds and offers better QoS compared with VPNs using static priority scheduling. An algorithm for active scheduling is described and simulation results are presented and compared with priority scheduling.

Abstract. The rapid evolution of real-time multimedia applications requires Quality of Service (QoS) based multicast routing in underlying computer networks. The constrained Steiner Tree, as the underpinning mathematical structure, is a well-known NP-complete problem. In this paper we investigate a variant of variable neighborhood search, variable descent search, for the delay-constrained least-cost multicast routing problems. The neighborhood structures designed in the variable descent search approaches are based on the idea of path replacement in trees. They are simple, yet effective operators, enabling a flexible search over the solution space of this complex problem with multiple constraints. A large number of simulations demonstrate that our algorithm is highly efficient in solving the delay-constrained, least-cost multicast routing problem in terms of both the total tree cost and the execution time. To our knowledge, this is the first study of variable neighborhood search on the delay-constrained, least-cost multicast routing problem. It outperforms other algorithms and heuristics over a range of problem instances. 1

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Many applications require send information from a source to multiple destinations through a communication network. To support these applications, it is necessary to determine a multicast tree of minimal cost to connect the source node to the destination nodes subject to delay constraints. Based on the Ant System algorithm, we present an ant algorithm to find the multicast tree that minimizes the total cost. In the proposed algorithm, the k shortest paths from the source node to the destination nodes are used for genotype representation. By comparing the results The expermintal results show that the algorithm can find optimal solution quickly and has a good scalability.