A new heuristic algorithm for finding minimum-cost multicast trees with bounded path delay

This paper presents a new heuristic algorithm called DDBMB (dynamic delay bounded multicast algorithm) to construct a minimum cost multicast tree. The heuristic depends on: (A) bounded delay along paths from source node to each destination node; (B) minimum cost of the multicast tree where the algorithm starts with the minimum delay tree and monotonically decreases the cost iteratively to construct a delay bounded minimum cost tree; and (C) dynamic multicast tree status which is maintained by updating the existing multicast tree when nodes in the network request join or leave. The construction of such constrained multicast tree is known as an NP-complete problem. Compared with other existing relative algorithms, the heuristic demonstrates a better average case behavior and can be very close to having a minimum cost depending on the delay bounds imposed.

In view of the free content distribution in multicast on Internet, a mechanism for constructing the minimum cost multicast routing tree is proposed based on the theory of economic mechanism design. The minimum cost multicast tree can minimize the total transmission cost of the tree, minimize the links connecting the specified multicast group members and save the data transmitting cost and network resources. The model of multicast networks is provided and a routing model based on minimum cost multicast tree is formulate. According to the existing multicast protocols, the design of an algorithm for implementing the routing mechanism is described. The mechanism is evaluated by means of a numerical example. Some prospects on the application of mechanism design theory in multicast research fields are presented.

A new heuristic algorithm is presented for constructing minimum-cost multicast trees with delay constraints. The new algorithm can set variable delay bounds on destinations and handles two variants of the network cost optimization goal: one minimizing the total cost (total bandwidth utilization) of the tree, and another minimizing the maximal link cost (the most congested link). Instead of the single-pass tree construction approach used in most previous heuristics, the new algorithm is based on a feasible search optimization method which starts with the minimum-delay tree and monotonically decreases the cost by iterative improvement of the delay-bounded tree. The optimality of the costs of the delay-bounded trees obtained with the new algorithm is analyzed by simulation. Depending on how tight the delay bounds are, the costs of the multicast trees obtained with the new algorithm are shown to be very close to the costs of the trees obtained by the Kou, Markowsky and Berman's algorithm (1981).

In a communication network with a source node, a multicast tree is defined as a tree rooted at the source node and all its leaves being recipients of the multicast originating at the source. The tree or bandwidth cost is normally measured by its utilization of tree links along with the quality of service (QoS) measures such as delay constraint and end-to-end delay. However, if nodes are allowed to join or leave the multicast group at any time during the lifetime of the multicast connection, then the problem is known as dynamic multicast routing problem. In this article, we combine a greedy approach with static multicast routing using Tabu Search to find a low-cost dynamic multicast tree with desirable QoS parameters. The proposed algorithm is then compared with several static multicast routing algorithms. The simulation results show that, on a large number of events, i.e., where nodes are leaving or joining, the proposed algorithm is able to find multicast trees of lower cost and more desirable QoS properties.

This paper considers the problem of constructing minimum-delay multicast trees for message dissemination in overlay networks in which nodal delays for processing messages are taken into account in addition to communication delays. The objective is to find a multicast tree to deliver a message from a source to multiple destinations in minimum delay time. This paper introduces a new delay measure called reception-and-processing delay that takes nodal processing delays into account for constructing multicast trees. In the process of constructing a multicast tree, the branches of the multicast tree may intersect or overlap with each other. An efficient method is devised to avoid this undesirable phenomenon. Several heuristic algorithms are developed for constructing multicast trees. The performances of the heuristic algorithms are studied via simulation. Our simulation results show that constructing the multicast tree by iteratively attaching the destination node with the smallest reception-and-processing delay to the current multicast tree yields the lowest average multicast delay among the heuristic algorithms studied in this paper.

This paper is concerned with a restricted version of minimum cost delay-constrained multicast in a network where each link has a delay and a cost. Given a source vertex $s$ and $p$ destination vertices $t_1, t_2, \ldots, t_p$ together with $p$ corresponding nonnegative delay constraints $d_1, d_2, \ldots, d_p$, many QoS multicast problems seek a minimum cost multicast tree in which the delay along the unique $s$--$t_i$ path is no more than $d_i$ for $1 \le i \le p$. This problem is NP-hard even when the topology of the multicast tree is fixed. In this paper we show that every multicast tree has an underlying Steiner topology and that every minimum cost delay-constrained multicast tree corresponds to a minimum cost delay-constrained realization of a corresponding Steiner topology. We present a fully polynomial time approximation scheme for computing a minimum cost delay-constrained multicast tree under a Steiner topology. We also present computational results of a preliminary implementation to illustrate the effectiveness of our algorithm and discuss its applications.

The optimal multimedia multicast routing problem is to determine a multicast tree of minimal cost to connect a given source node to a given set of destination nodes while fulfilling the delay requirement for multimedia information. This problem has been shown to be NP-complete (Kompella et al., 1993), and hence fast and good heuristic algorithms must be used in practice for a reasonable network size. The authors derive a lower bound on the cost of the optimal multicast trees by Lagrangean relaxation and problem decomposition. The numerical results for some standard test problems demonstrate that the lower bound is very tight and differs from the optimal solutions by only a few percent on average. In addition, the lower bound can be computed quite quickly and the computation time on a SUN workstation is only a few minutes for the networks with 100 nodes. This tight lower bound can be used to evaluate whether any given heuristic algorithm for multimedia multicast routing is close-to-optimal.

We consider a network design problem, where applications require various levels of quality-of-service (QoS) while connections have limited performance. Suppose that a source needs to send a message to a heterogeneous set of receivers. The objective is to design a low cost multicast tree from the source that would provide the QoS levels (e.g., bandwidth) requested by the receivers. We assume that the QoS level required on a link is the maximum among the QoS levels of the receivers that are connected to the source through the link. In accordance, we define the cost of a link to be a function of the QoS level that it provides. This definition of cost makes this optimization problem more general than the classical Steiner tree problem. We consider several variants of this problem all of which are proved to be NP-hard. For the variant where QoS levels of a link can vary arbitrarily and the cost function is linear in its QoS level, we give a heuristic that achieves a multicast tree with cost at most a constant times the cost of an optimal multicast tree. The constant depends on the best constant approximation ratio of the classical Steiner tree problem. For the more general variant, where each link has a given QoS level and cost we present a heuristic that generates a multicast tree with cost O(min{logr,k}) times the cost of an optimal tree, where r denotes the number of receivers, and k denotes the number of different levels of QoS required. We generalize this result to hold for the case of many multicast groups.

It is a challenging task to provide an easy–to-use programming interface for distributed shared memory in parallel computing that demands high availability as well as effective synchronization. The current implementations typically use conventional Ethernet as communication medium using broadcast or multicast for synchronization mechanisms. In general, multicast is more efficient than broadcast, as it uses multicast tree to transfer data instead of multicast flooding. Multicast avoids redundant transmissions and lessens network contention. These properties make it significant for distributed shared memory. However, such solution has limited control on response time and process scheduling. This causes uncertainty of time spent in synchronization and interruption of unrelated processes in the same multicast group. In this research, we propose a dynamic SDN multicast mechanism to improve efficiency of synchronization for distributed shared memory by using an SDN-based multicast mechanism and a dynamic core based tree algorithm. The forwarding rule reduces the number of consistency-related messages without interfering the unrelated processes in the same multicast group. The dynamic core-based tree algorithm builds a multicast tree for every multicast group, hereby, SDN controller dynamically adjusts multicast tree according to joining or leaving of nodes. The experiments on the prototype system demonstrate that it could provide better performance compared to the conventional Ethernet based solution in terms of response time and process scheduling in the homogeneous testing environment.

For many multimedia multicast applications, especially those requiring real-time traffic, it is important that the maximum delay bound requirement between any pair of group members be satisfied. Most studies on multicast routing have been based on a single multicast tree (a shortest path tree or a minimal Steiner tree) approach. By using only a single multicast tree for a multicast group, satisfying the maximum delay bound requirement is nearly impossible. To fulfill these requirement, we adopt the multiple multicast tree concept whose disadvantage is the high tree maintenance cost. Since the tree maintenance cost is proportional to the number of multicast trees for a multicast group, it is necessary to minimize the number of multicast trees. In this paper, we formulate the delay-bounded multicast tree (DBMT) problem whose main objectives are to satisfy an application's maximum delay bound among the group members and to minimize the number of multicast trees needed for a group communication. We categorize the DBMT problem according applications' needs into two subproblems, the shortest path tree-based DBMT (SPT DBMT) and the minimal Steiner tree-based DBMT (MST DBMT) problems. For the DBMT subproblems, we prove the NP-hardness and propose heuristic algorithms. For the performance analysis, simulations were performed.

Group multicast routing problem (GMRP) is a generalization of multicasting whereby every member of the group is allowed to multicast messages to other members from the same group. The routing problem in this case involves the construction of a set of low cost multicast trees with bandwidth requirements for all the group members in the network. The traditional solutions only care for the low cost of multicast trees and sometimes the algorithms will fail during the construction due to the inefficiency of the bandwidth allocation. In this paper we study the feasible solutions to GMRP by proposing a new algorithm to improve the success rate of constructing multicast trees. Simulation results show that our new algorithm performed better in terms of bandwidth utilization and success rate of building multicast trees compared with existing algorithms.

Multicast group communication has many advantages in data centers and thus is widely used by many applications. It can efficiently reduce the network traffic and improve the application throughput. For the multicast application in data centers, an essential problem is how to find a minimal multicast tree, which has been proved to be NP-hard. In this paper, we propose an approximation tree-building method for the minimal multicast problem, named HD （Hamming Distance）-based multicast tree. Consider that many new network structures have been proposed for data centers. We choose three representative ones, including BCube, FBFLY, and HyperX, whose topological structures can be regarded as the generalized hypercube. Given a multicast group in BCube, the HD-based method can jointly schedule the path from each of receiver to the only sender among multiple disjoint paths; hence, it can quickly construct an efficient multicast tree with the low cost. The experimental results demonstrate that our method consumes less time to construct an efficient multicast tree, while considerably reduces the cost of the multicast tree compared to the representative methods. Our approach for BCube can also be adapted to other generalized hypercube network structures for data centers after minimal modifications.

Internet research community has proposed many Different multicast routing protocols to support efficient multimedia application such as, IPTV, videoconferencing, group games. Nevertheless, these protocols have not been designed for mobile roaming members and sources, and has not been tested in wireless and mobile environment since they were developed for multicast parties whose members and sources are topologically stationary. Recently, as the performance of mobile hosts rapidly improves and the bandwidth of wireless access networks grows up, the expectation for mobile multimedia communication services including many-to-many communications such as video-conferencing begins a big necessary. Studying and solving multicast issues in the stationary multicast infrastructure has been largely studied in the literature. However, fewer efforts have been spent in the specific problems of mobile members and sources caused by the frequent change of membership and point of attachment. This paper addresses the issue of mobile Multicast routing by presenting a Fast Dynamic Multicast Tree Adjustment Protocol for Mobile IPv6 (FDMTA-MIPv6), an optimized multicast tree protocol is proposed to transform multicast tree into an optimal shared multicast tree routed at a selected RP. To estimate and evaluate our scheme, we implement simulation based in many metrics, simulation results show that good performance is achieved in terms of handoff latency, end-to-end delay, tree construction delay and others metrics.

With the proliferation of multimedia group applications, the construction of multicast trees satisfying quality of service (QoS) requirements is becoming a problem of prime importance. Many of the multicast applications (such as video broadcasts and teleconferencing) require the network to support dynamic multicast sessions wherein the membership of the multicast group changes with time. We propose and evaluate an algorithm for on-line update of multicast trees to adjust to changes in group membership. The algorithm is based on a concept called quality factor (QF) that represents the usefulness of a portion of the multicast tree to the overall multicast session. When the usefulness of a particular region of the tree drops below a threshold, a rearrangement technique is used to suitably modify the tree. This algorithm aims to satisfy the delay-constraints of all current group members, at the same time minimizing the cost of the constructed tree. We compare the performance of our algorithm, by simulation, with that of an off-fine Steiner heuristic; with ARIES, a previously published algorithm for on-line update of unconstrained trees; and with the algorithm proposed by Hong, Lee and Park (see Proc. of IEEE INFOCOM, pp. 1433-40, 1998) for on-line update of delay-constrained trees. The simulation results indicate that our algorithm provides excellent cost-competitiveness that is better than that provided by the algorithm described by Hong et al., minimizes changes in the multicast tree after each update, and performs favorably even when compared with the unconstrained ARIES heuristic.

The basis of multicast data transmission is to construct a multicast tree. The main problem concerning the construction of a multicast tree is the selection of the root of the shared tree or the core point. Therefore, the algorithm we propose guarantees that the delay from the source to any destination does not exceed a real-time constraint satisfying the delay-variation constraint under cost minimization. The core selection function in this algorithm achieves a balance of optimizing cost and delay of the multicast tree. Simulation results show that the algorithm has low complexity and balances between the computational complexity and performance.