Topology Optimization for Heterogeneous DHT-Based Multicast

Many applications can benefit from the use of multicast to distribute content efficiently. Due to the limited deployment of network-layer multicast, several application-layer multicast schemes have been proposed. In these schemes, the nodes in the multicast tree are end systems which are typically connected to the network by a single access link. Transmissions to the children of a node in the multicast tree have to share this single uplink, a factor largely ignored by previous work. In this work, we examine the effect of access link scheduling on the latency of content delivery in a multicast tree. Specifically, we examine the general case where multiple packets (comprising a block of data) are sent to each child in turn. We provide an analytical relation to compute the latency at a node in the multicast tree and show the relationship to the packet size and block size used to transfer data. We propose heuristics for tree construction which take link serialization into account. We evaluate this effect using simulations and show that using larger block sizes to transfer data can reduce the average finish time of the nodes in the multicast tree at the expense of slightly increased variance.KeywordsPeer-to-peer networksMulticast

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.

Large parts of the Internet are still incapable of native multicast, and ubiquitous deployment of multicast will take a long time. There are two approaches to provide wide-area multicast service in today’s Internet. One is tunneling approach and the other is application-level multicast approach. In this paper, we focus on application-level multicast approach and propose a new scheme which improves the performance penalties of application-level multicast by making use of network support. Because in application-level multicast, endhosts provide multicast functionality instead of routers, application-level multicast delivery tree is inherently less efficient than IP multicast tree. Therefore, in our scheme, the router on the application-level multicast delivery tree alters the tree based on network-level delivery path. We evaluate our scheme with simulation experiment. Our simulation results indicate that our scheme improves the performance of application-level multicast. Further we compare our scheme to the tunneling approach from the viewpoint of transmission performances. The results reveal applicable domains of both approaches.

A mobile ad hoc network (MANET) is a dynamically reconfigurable wireless network that does not have a fixed infrastructure. Due to the high mobility of nodes, the network topology of MANETs changes very fast, making it more difficult to find the routes that message packets use. Because mobile nodes have limited battery power, it is therefore very important to use energy in a MANET efficiently. In this paper, we propose a power-aware multicast routing protocol (PMRP) with mobility prediction for MANETs. In order to select a subset of paths that provide increased stability and reliability of routes, in routing discovery, each node receives the RREQ packet and uses the power-aware metric to get in advance the power consumption of transmitted data packets. If the node has enough remaining power to transmit data packets, it uses the global positioning system (GPS) to get the location information (i.e., position, velocity and direction) of the mobile nodes and utilizes this information to calculate the link expiration time (LET) between two connected mobile nodes. During route discovery, each destination node selects the routing path with the smallest LET and uses this smallest link expiration time as the route expiration time (RET). Each destination node collects several feasible routes and then selects the path with the longest RET value as the primary routing path. Then the source node uses these routes between the source node and each destination node to create a multicast tree. In the multicast tree, the source node will be the root node and the destination nodes will be the leaf nodes. Simulation results show that the proposed PMRP outperforms MAODV (Royer, E. M. & Perkins, C. E. (1999). In Proceedings of the ACM MOBICOM, pp. 207---218, August 1999.) and RMAODV (Baolin, S. & Layuan, L. (2005). In Proceeding of the 2005 IEEE International symposium on microwave antenna, propagation and EMC technologies for wireless communications, Vol. 2, pp. 1514---1517, August 2005.).

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.

There have been many geographic multicasting protocols proposed for wireless sensor networks (WSNs). These protocols tend to exploit a SOurce-initiated Geographic Multicasting (SOGM) approach which consists of three phases: first, a source collects the position information of all sink nodes; second, the source constructs a multicast tree through the position information; third, the source forwards data down the multicast tree. However, if a multicast group contains many mobile sinks, frequent movement of the sinks cause a huge number of link failures of the multicast tree. To fix them, the SOGM approach requires a great deal of delivery of position registration and update messages to the source, thus leads to significant energy consumption of the sensor nodes in the vicinity of the source. Moreover, since each sink asynchronously updates one's new position to the source, it is difficult for the source node to find an opportune time for reconstructing the multicast tree. In this paper, we propose a SInk-initiated Geographic Multicasting (SIGM) protocol for WSNs which can avoid these problems faced by the SOGM approach. The SIGM allows sinks to construct their own data delivery paths to a source, and a multicast tree is automatically constructed by merging the data delivery paths. Simulation results show that the proposed protocol is superior to other protocols in term of average energy consumption, it thus prolongs the network lifetime.

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.

A multi-path QoS multicast routing protocol with slot assignment for mobile ad hoc networks

Fuzzy priority based overlay multicast

This article presents a new heuristic algorithm called DDBMA lDynamic Delay Bounded Multicast Algorithmr to construct a minimum-cost multicast tree. The heuristic depends on l1r bounded delay along paths from source nodes to destination node; l2r minimum cost of the multicast tree; l3r dynamic multicast tree status which is maintained by updating the existing multicast tree when nodes in the network request to join or leave. Copyright © 1999 John Wiley & Sons, Ltd.

Multicast routing is establishing a tree which is rooted from the source node and contains all the multicast destinations. A multicast routing tree with multiple QoS constraints may be the tree in which the delay, delay-jitter, packet-loss and bandwidth should satisfy the pre-specified bounds. This paper presents a hierarchical QoS multicast routing protocol (HQMRP) for mobile ad-hoc networks. It can provide QoS-sensitive routes in a scalable and flexible way, in the network environment with mobility. In the proposed HQMRP scheme, each local node just only needs to maintain local multicast routing information and/or summary information of other clusters (or domains), but does not requires any global ad hoc network states to be maintained. The HQMRP attempts to significantly reduce the overhead of constructing a multicast tree with multiple QoS constraints. The performance measures of HQMRP are evaluated using simulation. Simulation results show that HQMRP is an available approach to multicast routing decision for mobile ad-hoc networks.

Recently, application-layer multicast (ALM) has emerged as a means to solve most of the problems of IP-based multicast. Topology-aware approach of ALM is more attractive because it exploits underlying network topology data to construct multicast overlay networks. In this paper, a novel overlay network construction mechanism called balanced multi-domain topology-aware grouping (BMTAG) is introduced. BMTAG adopts a special node (domain monitor) to be the parent of all other nodes in the same domain. The mechanism can not only save the time used to discover the topology and execute the path matching algorithm but also lower the depth of the multicast tree. Building a multicast tree with balanced traffic to avoid the bottleneck is another purpose of BMTAG. Simulation results show that BMTAG can get higher performance than TAG especially when the group size is large or the percentage of domain nodes is high.

We present a balanced and unbalanced binary-tree model to explore the delay performance of feedback synchronization algorithms for multicast ABR flow control. Using this model, we analyze the feedback-delay performance scalability of the soft-synchronization protocol (SSP), which derives a single consolidated RM (resource management) cell at each multicast branch-point from feedback RM cells of different downstream branches that are not necessarily responses to the same forward RM cell. In contrast with the other existing schemes, SSP is shown to be able to effectively support synchronization of feedback RM cell and make the effective RM cell roundtrip time (RTT) virtually independent of the multicast tree's topology. Also derived is the optimal RM-cell update interval for SSP to minimize RM-cell RTTs for a given multicast tree.

A near-optimal multicast scheme for mobile ad hoc networks using a hybrid genetic algorithm

Multicast is an efficient method for transmitting the same packets to a group of destinations. In energy-constrained wireless ad hoc networks where nodes are powered by batteries, one of the challenging issues is how to prolong the multicast lifetime. Most of existing work mainly focuses on multicast lifetime maximization problem in wireless packet loss-free networks. However, this may not be the case in reality. In this paper, we are concerned with the multicast lifetime maximization problem in unreliable wireless ad hoc networks. To solve this problem, we first define the multicast lifetime as the number of packets transmitted along the multicast tree successfully. Then we develop a novel lifetime maximization genetic algorithm to construct the multicast tree consisting of high reliability links subject to the source and destination nodes. Simulation results demonstrate the efficiency and effectiveness of the proposed algorithm.