Balanced multi-domain topology-aware overlay networks in application-layer multicast

Building a multicast tree in an overlay network is the major problem in application layer multicast. In a selfish overlay network, the end hosts may not be cooperative. They are willing to maximize their own benefits instead of being loyal to the protocol or altruistically contributing to the benefits of the whole overlay network. In this paper, we design a strategyproof mechanism in building a truthful minimum cost multicast tree in the mesh-tree way, which could simplify the overlay construction and maintenance. We model the network in both simple and general cost model. We conduct simulation to study the relationship between utility of cheating node and other nodes

The geographically distributed system can be interconnected via an overlay multicast network. In this overlay network the multicast data are routed and replicated on the application layer along a multicast tree. This paper presents the techniques of the network reduction and the multicast tree construction. The multicast tree in the form of shortest path tree (SPT) can be build up upon the linear programming formulation. To control the load of each host, the additional constraints on the maximal number of directly outgoing connections and integer variables are added and subsequently form the degree-bounded shortest path tree problem (db-SPT). This theoretically based problem is formulated in integer linear programming framework

Video streaming services over the Internet are growing rapidly owing to the broadbandization of various networks. However, in such systems where a large number of users simultaneously access the same contents server, the convergence of the network traffic and service requests presents a significant problem. From this point of view, application layer multicast (ALM) has recently attracted much attention due to its scalability and feasibility in the current network systems. In ALM, user nodes construct a multicast tree structure to efficiently deliver an identical video streaming content. Various techniques to construct ALM trees have been designed to achieve improved performance in terms of shorter delay and higher reliability. However, in most of the existing ALM schemes, the performance in channel switching events has not been studied sufficiently; channel switching can be considered as the combination of the procedures for departing from the current and joining the future ALM trees, respectively. In general, node joining and departure processes take a certain time, which can be increased significantly depending on the network conditions whereby users are left waiting for the start of a new program on the switched channel. Therefore, reducing the channel switching delay is a significant issue in multichannel video streaming in ALM. In this paper, we propose a multichannel streaming scheme to reduce channel switching delay in ALM. Our scheme is based on an advanced ALM method dubbed network-aware hierarchical arrangement graph, which constructs node-disjoint multicast trees by utilizing the arrangement graph theory to achieve high robustness on node departures. The performance of the proposed scheme is verified through extensive computer simulations, which demonstrate that our proposed scheme succeeds in reducing the delay in channel switching without system throughput degradation.

Despite the availability of high bandwidth Internet access for end-users, video broadcasting over the Internet is not widely spread. Multicast communication decreases the network load by eliminating redundancy of the data transfer. However IP multicast was never widely accepted by commercial Internet service providers (ISP). Existing solutions solving this problem, like MBONE tunneling, are not available for end-users accessing the Internet via xDSL or TV cable. Application layer multicast using peer-to-peer (P2P) overlay networks could solve the problem of sparse IP multicast support in the Internet. A limitation of this approach is the lack of standardized interfaces for existing IP multicast applications. We propose a solution, which bridges application layer multicast and IP multicast and uses a P2P (overlay) network to transport multicast data. Our solution - including a proof-of-concept prototype - enables video broadcasting over the Internet using existing IP multicast applications without requiring additional service deployment.

The purpose of this study is to construct a robust and stable overlay tree of ALM (Application Layer Multicast) for real-time video transmission. Firstly, we propose a proactive route maintenance which enables fast recovery of the overlay tree against node departures and failures. By forcing free node degrees for route backup, signaling overheads for route maintenance can be reduced in a scalable manner. Secondly, we improve performance of the proposed method by introducing layered video coding. Smooth layer management instead of coarse degree management contributes to reduction of the depth of overlay tree (i.e. delay) as well as to efficient bandwidth utilization. Thirdly, we introduce session records of each node into the overlay tree construction. Long-term history of user access records is expected to bring more robust overlay trees. Finally, we carried out extensive evaluation experiments. Simulations and implementations demonstrate that our methods lead to fast recovery of the overlay tree against node departures and reduction of the signaling overheads. Furthermore, introduction of layered video coding is proved to be efficient to reduce delays, to improve bandwidth utilization and to avoid severe degradation of picture quality. Final experiments show that incorporation of node stability reduces the number of nodes affected by parent node departures by promoting adequate nodes to upper layer of the ALM tree.

International audience

Collaborative virtual environments (CVEs) such as massive multiuser 3D games and military training environments can place strict requirements on networks when participating users share the 3D virtual environment through mobile devices in an ad-hoc network. In this paper, the authors show how a CVE application can benefit from the application layer multicast when deployed on the Gnutella peer-to-peer network over an ad-hoc network. The authors propose a protocol called GALM (Gnutella application layer multicast). GALM requires no infrastructure support such as a multicast router to maintain the group state. It has the following characteristics: a) it is adaptable to mobility and network group size by managing the mobile device resources by using gateway node, b) it is reliable; the CVE application can choose at a running time the adequate transport protocol for each data type - for example, using TCP for scene and object data and RTP to send video and audio data, c) it is independent from the lower layer; any link failure or mobility in the physical layer will not affect the application layer, eliminating the need to perform a multicast tree reconfiguration, d) it has link quality; therefore, a cross layer can be used between the network and the application layer in order to provide optimal paths in the multicast tree configuration process. In addition, the protocol handles tolerance to mobility and multicast tree recovery using a smart logical Gnutella network that is based on a novel discovery technique in which mobile nodes are found by means of both their state and position in the CVE.

It is crucial to use an efficient network-aware overlay network to enable Internet-scale multicast streaming service to adjust under the dynamic underlying network conditions and overlay node churn without extensive network measurements. We utilize our previously proposed network-aware SuperPeers-Peers geometric overlay network hierarchy which exploits the underlying network locality and proximity of the nodes, to build massive scale overlay multicast streaming network (Bos). We create source routed overlay multicast tree from the resulting optimal geometric routing paths based on the shortest geometric distances between SuperPeers at the SuperPeers layer. The overlay multicast tree is self-healed locally in a distributed manner using an ancestor-recovery protocol. The high bandwidth multicast backbone infrastructure at the SuperPeers layer will serve the Peers in the lower layer. We evaluate Bos on ten massive scale networks each consisting of 100,000 nodes and in the PlanetLab. Our massive scale overlay multicast performance results show high efficiency and good scalability.

It is proved that network coding can achieve multicast capacity and therefore improves the throughput of a multicast network significantly. This chapter will focus on applying network coding to Application layer multicast(ALM). The benefits are two folds: first, ALM is built on peer-to-peer networks whose topology can be arbitrary so it is easy to tailor the topology to facilitate network coding; second, the nodes in ALM are end hosts which are powerful enough to perform complex encoding and decoding operations.

Application layer multicast (ALM) is highly expected to replace IP multicasting as the new technological choice for content delivery. Depending on the streaming application, ALM nodes will construct a multicast tree and deliver the stream through this tree. However, if a node resides in the tree leaves, it cannot deliver the stream to its descendant nodes. In this case, quality of service (QoS) will be compromised dramatically. To overcome this problem, topology-aware hierarchical arrangement graph (THAG) was proposed. By employing multiple description coding (MDC), THAG first splits the stream into a number of descriptions, and then uses arrangement graph (AG) to construct node-disjoint multicast trees for each description. However, using a constant AG size in THAG creates difficulty in delivering descriptions appropriately across a heterogeneous network. In this paper, we propose a method, referred to as network-aware hierarchical arrangement graph (NHAG), to change the AG size dynamically to enhance THAG performance, even in heterogeneous networks. Finally, we evaluate the proposed scheme by experiments using the network simulator ns-2. By comparing our proposed method to THAG and SplitStream, we show that our method provides better performance in terms of throughput and QoS. The results indicate that our approach is more reliable than other methods in heterogeneous networks.

Various streaming services have been gaining much attention in the Internet. In order to reduce the investment cost many companies decide to offer the streaming by the use of the application-layer multicasting constructed on the top of an overlay network. In this paper we address the problem of overlay networks design. The main goal is to minimize the cost of access links selected for nodes participating in the application-layer multicasting. The second objective is to minimize the network delay, which is mainly caused in the Internet by inter-ISP (Internet Service Providers) transmissions. Therefore, in the optimization model the underlying network is composed of ISPs. The idea is to provide enough upload capacity within each ISP in order to reduce the number of links between ISPs. The optimization problem is formulated as an Integer Program. We use optimal methods (branch-and-cut algorithm included in CPLEX) as well as our own heuristic that yields results very close to optimum. Moreover, we use simulations to examine the tradeoff of the delay-aware approach in terms of the cost and the number of inter-ISP links.

Application layer multicast (ALM) is an effective group communication method. The ALM tree is usually built in a distributed manner because of its good scalability. However, the distributed ALM solution sometimes produces a low performance delivery tree. In this paper, we propose an ALM tree optimization solution, named ALMTO, for multicast applications, in particular, those with a large number of concurrent users. ALMTO manages and optimizes the ALM tree in the following four steps: 1) periodic collection of related structure information, based on a proposed structure report domain model and special tree structure; 2) construction and maintenance of a logical ALM tree, in terms of the collected structure information; 3) central computation of the ALM tree optimization scheme, according to the logical ALM tree and optimization objective corresponding to the specific multicast application; and 4) reshaping of the real ALM tree in terms of the optimization scheme. We analyze the problem of the centralized tree optimization scheme orchestration and present an effective solution that can adapt to the dynamics of group members. We also present two approaches: 1) degree-bounded connection-keeping tree transformation and 2) ring-based data compensation to ensure that the ALM tree can be reliably transformed.

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.

Recently, IPTV service has attracted significant attentions to both of the ISPs and normal users,and the quality of experience (QoE) from the users point of view is the most important evaluation for IPTV service provider. A reasonable peer selection mechanism of P2P based IPTV service can provide the end-users with a better QoE in a limited network resource environment. Therefore, the cross-layer parameters relationships modeling exhibits its significance for peer choosing decision. In order to gain insights into tree-push P2P IPTV systems, we have undertaken an in-depth measurement study of application layer multicast (ALM) tree structure. Great quantity of packet traces for cross-layer metrics in various measurement scenarios, including both CERNET and NSFCnet, are collected and analyzed based on which a novel peer selection algorithm is expressed. Finally, we figure out the priority of important P2P application factors for the development and deployment of future P2P IPTV systems.

Overlay networks are considered an easy and effective way to deploy value-added Internet services by extending the best-effort delivery service supported by IP layer. However, a careful design is needed in order to take advantage of these benefits. Since there are no standards for overlay networks yet, they are often independently designed, which means that each one applies its own topology discovery and takes its own routing decisions. As a result, they may negatively affect each other by generating control overhead and by creating bottlenecks in the physical network. In order to avoid such a situation, this work proposes an overlay network organization and architecture towards a middleware for overlay multicast services. As proof of concept, we have deployed a multicast service overlay network taking advantage of this architecture and considering both intradomain and interdomain scenarios – the latter being practically impossible to deploy on public networks due to administrative issues. By experimental measurements, we validate interdomain multicast functionality over four autonomous systems without any native support from underlying networks.