A comparative study of multicast protocols: top, bottom or in the middle?

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.

Multicasting is the data distribution from one sender to a group of receivers. Traditionally multicasting is implemented at network layer, in the way that routers perform membership management, maintain data delivery path, and replicate and forward data. IP multicast is the most efficient way for group data distribution. However, it has been shown that it is extremely difficult to deploy IP multicast at a large scale. Therefore an alternative has been proposed to shift multicast support to the application layer. This approach expects end-hosts participating in the application to perform multicast functions. This is application layer multicasting (ALM). This paper proposes a proxy-based single source ALM protocol which targets media streaming applications, where latency is the overlay building metric. A text-based message exchange application is implemented based on this protocol. Some measurements are taken both on the intranet and on the Internet. And some performance data are provided. Finally we concluded our research

As an alternative of IP Multicast, ALM implements multicast functionality at the application layer instead of the IP layer, which addresses the problem of non-ubiquitous deployment of IP multicast. However, the reliability of ALM is low because dynamic hosts forward the data. This paper analyzes the error and delivery features of ALM trees, and further presents a data loss recovery solution (called HBHLR) for application layer multicast.

IP multicast is a technique that can transmit one copy of data traffic to multiple receivers at one time. Because it can greatly save the network bandwidth consumption and many applications are inherently multicast-based, it has been a research focus since the idea was proposed. However, because of many reasons, such as management, security, inter-domain routing, etc, it has not been widely deployed. Recently, many researchers have put their research focus on overlay multicast. In overlay multicast, the data replication, multicast routing, group management and other functions are all achieved at application layer. Because it does not require any change to the current Internet infrastructure, it can be easily deployed. Since the idea was proposed, many overlay multicast ideas have been proposed. In this paper, we propose a method for reliable data transfer on overlay multicast. It applies TCP at transfer-layer and local data buffering at application-layer. This paper explains the advantages and disadvantage of using TCP for reliable data transfer on overlay multicast, then, describes the operation of our method and induces an optimal buffer size in dynamic nodes based overlay multicast. Finally, we check the effect of data buffering with experiments on several models.

Multicast services can be provided either as a basic network service by IP multicast or as an application layer service called overlay multicast. How to build an efficient data delivery structure is the most critical problem for overlay multicast, which depends on a good routing algorithm. Many routing algorithms have been presented recent years. Some algorithms modeled overlay multicast's routing problem as a degree constrained spanning tree problem based on undirected completed graph, and some others were built on some special peer to peer routing protocols. However, detecting and obtaining a completed graph's all network state information needs consume expensive cost and restricts its scalability and sometime be impossible. On the contrary these routing algorithms built on p2p scheme are of good scalability but maybe fail in practical applications. This paper redefines the overlay multicast routing problem as to find a degree constrained sub-tree with minimum delay optimization for a general undirected connected graph not a completed graph. It is a NP-hard problem. A heuristic genetic algorithm for this problem is given and the simulation results verify its effectiveness.

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.

Native IP multicast would be the best solution to distribute live streaming contents among various destinations since the real-time nature of such applications usually imposes strict delay constraints. Application Layer Multicast (ALM) platforms are emerging as a solution to overcome the well-known lack of a globally supported native multicast. Since the development of ALM applications is slowed by complexity and portability issues, we designed an open source C library framework that takes care of RTP/RTCP technical details and fosters a modular and higher level design. Besides it frees ALM developers from spending time in porting operations from Unix to Windows operating systems.

After a decade of research and development, IP multicast has still not been deployed widely in the global Internet due to many open technical issues: lack of admission control, poorly scaled with large number of groups, and requiring substantial infrastructure modifications. To provide the benefits of IP multicast without requiring direct router support of the presence of a physical broadcast medium, various application level multicast (ALM) models have been attempted. However, there are still several problems with ALM: unnecessary coupling between an application and its multicasting supports, bottleneck problem at network access links and considerable processing power required at the end nodes to support ALM mechanisms. This paper proposes an architecture to address these problems by delegating application-multicasting support mechanisms to smart edge devices associated with the application end nodes. The architecture gives rise to an interesting edge device any-casting technology that lies between the IP-multicasting and the application layer multicasting and enjoys the benefits of both. Furthermore, the architecture may provide sufficient cost-benefit for adoption by service providers. The paper presents initial results obtained from the implementation of a video streaming application over the testbed that implements the proposed architecture.

Group communication facilitates efficient data transmission to numerous receivers by reducing data replication efforts both at the sender and in the network. Group communication is used in today’s communication networks in many ways, such as broadcasting in cellular networks, IP multicast on the network layer, or as application layer multicast. Despite many efforts in providing data origin authentication for specific application areas in group communication, no efficient and secure all-purpose solution has been proposed so far.

Patching is a effective multicast video scheduling scheme for VOD service. However, the video server bandwidth requirement will increase greatly when client request rate is high. On the other hand, IP multicast can only be implemented in a relatively small area nowadays. Aiming at these problems, we present a novel video stream scheduling scheme: Range Patching based on overlay multicast technology which is a very good alternative technology for IP multicast implemented on application layer. In Range Patching, the patching operation is transferred from the server to overlay nodes using the fixed and temporary cache of overlay node. Simulation results show that Range Patching can significantly reduce the bandwidth consumption when the segment number is small. In addition, when client's request rate is relatively low, the Range Patching scheme can get better performance than Standard Patching, Double Patching and Batched Patching.

Many research issues have been raised in Application Layer Multicasting (ALM), such as group management, security, integrity of data, link stress, link stretch, load balancing, fault tolerance and scalability, because of the shifting of the multicast protocol from the IP layer to the application layer. To address these issues many protocols have evolved by changing their topology structure. In this paper, the POSET protocol stack is proposed, which consists of three layers, such as communication control, POSET cube, and content distribution. The novelty of this paper is the lattice-based data distribution with POSET cube architecture. The results have been compared with the existing NICE and Narada protocols. The experimental results show that the proposed POSET protocol improves throughput between 7.14% and 40% and decreases the delay between 7.69% and 25%, compared to the existing NICE protocol.

This paper proposes a set of novel distributed algorithms on m-D mesh overlay configurations for short delay and low resource consumption application layer multicast. In contrast to previous approaches, our application layer multicast adopts two-layer tree architecture and the novelty and contribution are: (1) cluster formation algorithm assigns the closest group members into the same cluster that greatly decreases the multicast delay and resource consumption caused by the message transmission among the members with long distances; (2) optimal core selection algorithm seeks the cluster member who has the minimum sum of static delay distances to other cluster members as the optimal cores (i.e. cluster cores) that guarantees the short multicast delay; (3) weighted shortest path tree generation algorithm constructs a shortest path tree rooted at the optimal core for each cluster. The shortest path tree utilizes the minimum sum of links that are on the shortest paths among the cluster members; and (4) distributed multicast routing algorithm directs the multicast messages to be efficiently distributed along the two-layer multicast architecture in parallel without a global control. The extended simulation results indicate that the application layer multicast constructed by our algorithms is efficient in terms of short multicast delay and low network resource consumption as compared with other well-known existing multicast solutions.

Tree-based overlay multicast is an effective group communication method for media streaming applications. However, a group member’s departure causes all of its descendants to be disconnected from the multicast tree for some time, which results in poor performance. The above problem is difficult to be addressed because overlay multicast tree is intrinsically instable. In this paper, we proposed a novel stability enhancing solution, VMCast, for tree-based overlay multicast. This solution uses two types of on-demand cloud virtual machines (VMs), i.e., multicast VMs (MVMs) and compensation VMs (CVMs). MVMs are used to disseminate the multicast data, whereas CVMs are used to offer streaming compensation. The used VMs in the same cloud datacenter constitute a VM cluster. Each VM cluster is responsible for a service domain (VMSD), and each group member belongs to a specific VMSD. The data source delivers the multicast data to MVMs through a reliable path, and MVMs further disseminate the data to group members along domain overlay multicast trees. The above approach structurally improves the stability of the overlay multicast tree. We further utilized CVM-based streaming compensation to enhance the stability of the data distribution in the VMSDs. VMCast can be used as an extension to existing tree-based overlay multicast solutions, to provide better services for media streaming applications. We applied VMCast to two application instances (i.e., HMTP and HCcast). The results show that it can obviously enhance the stability of the data distribution.

CoolStreaming is the first protocol which introduces the mesh structure into Application Layer Multicast(ALM) in media streaming application, i.e. each agent may have two or more parents instead of only one parent. However, since the agents in Mesh-based ALM(MALM) are strategy and selfish, the effect of cheating behavior may not be ignored. To solve this problem, we apply the VCG mechanism design into MALM network model, and devise a strategyproof mechanism to avoid the agent cheating. As a result, the goal to maximize the system outcome can be achieved. In addition, we design a distributed algorithm to realize our mechanism. The algorithm can dynamically adapts to form a better multicast mesh, though ALM network parameters and constraints change dynamically in reality. The correctness and performance of this distributed algorithm are verified by the following experimental results.

IPTV will be one of the main drivers of network innovation in the near future. Its bandwidth demands, especially if combined with HDTV, require smart algorithms for content distribution. One approach that is currently discussed intensively is Application Layer Multicast (ALM), which allows to scale to large node numbers by incorporating the resources of participating peers. In addition, locality-aware ALM approaches can distribute content close to the edges of the network and thus are able to relieve core networks from traffic. In this work, we propose to combine ALM with virtual routers that assist in content distribution, so-called ALM-Routers. They can be moved between distinct network positions and are inspired by current research towards a future Internet. Furthermore, we propose adaptation algorithms that operate solely on local knowledge and optimize ALM-Router positions as well as their overlay neighborhood. As our simulation results indicate, already a small fraction of such virtual nodes deployed on core network routers, decrease the overall traffic amount. Moreover, a subsequent optimization of the positions of ALM-Routers and the optimization of their overlay neighborhood induces additional considerable traffic savings compared to a static placement.