This paper presents the design, implementation and performance of a reliable multicast transport protocol called RMTP. RMTP is based on a hierarchical structure in which receivers are grouped into local regions or domains and in each domain there is a special receiver called a Designated Receiver (DR) which is responsible for sending acknowledgments periodically to the sender, for processing acknowledgements from receivers in its domain and for retransmitting lost packets to the corresponding receivers. Since lost packets are recovered by local retransmissions as opposed to retransmissions from the original sender, end-to-end latency is significantly reduced, and the overall throughput is improved as well. Also, since only the DRs send their acknowledgments to the sender, instead of all receivers sending their acknowledgments to the sender, a single acknowledgement is generated per local region, and this prevents acknowledgement implosion. Receivers in RMTP send their acknowledgments to the DRs periodically, thereby simplifying error recovery. In addition, lost packets are recovered by selective repeat retransmissions, leading to improved throughput at the cost of minimal additional buffering at the receivers. This paper also describes the implementation of RMTP and its performance on the Internet.

We describe a new scalable application-layer multicast protocol, specifically designed for low-bandwidth, data streaming applications with large receiver sets. Our scheme is based upon a hierarchical clustering of the application-layer multicast peers and can support a number of different data delivery trees with specific desirable properties. We show that group members maintain state for a constant number of other membersand the control overhead is also a constant.

IP multicast offers scalable point-to-multipoint delivery necessary for using group communication applications on the Internet. However, the IP multicast service has seen slow commercial deployment by ISPs and carriers. The original service model was designed without a clear understanding of commercial requirements or a robust implementation strategy. The very limited number of applications and the complexity of the architectural design — which we believe is a consequence of the open service model — have deterred widespread deployment as well. We examine the issues that have limited the commercial deployment of IP-multicast from the viewpoint of carriers. We analyze where the model fails, what it does not offer, and we discuss requirements for successful deployment of multicast services. 1

This paper presents a novel multicast routing protocol for mobile ad hoc wireless networks. The protocol, termed ODMRP (On-Demand Multicast Routing Protocol), is a mesh-based, rather than a conventional treebased, multicast scheme and uses a forwarding group concept (only a subset of nodes forwards the multicast packets via scoped flooding). It applies on-demand procedures to dynamically build routes and maintain multicast group membership. ODMRP is well suited for ad hoc wireless networks with mobile hosts where bandwidth is limited, topology changes frequently, and power is constrained. We evaluate ODMRP's scalability and performance via simulation.

Layered Video Multicast with Retransmissions (LVMR) is a system for distributing video using layered coding over the Internet. The two key contributions of the system are: (1) improving the quality of reception within each layer by retransmitting lost packets given an upper bound on recovery time and applying an adaptive playback point scheme to help achieve more successful retransmission, and (2) adapting to network congestion and heterogeneity using hierarchical rate control mechanism. This paper concentrates on the rate control aspects of LVMR. In contrast to the existing sender-based and receiver-based rate control in which the entire information about network congestion is either available at the sender (in sender-based approach) or replicated at the receivers (in receiver-based approach), the hierarchical rate control mechanism distributes the information between the sender, receivers, and some agents in the network in such a way that each entity maintains only the info...

Without a doubt, multicast communication---the one-to-manyormany-to-many delivery of data---has become a hot topic. It is of interest in the research community, among standards groups, and to network service providers. For all the attention multicast has received, there are still issues that have not been completely resolved. One result is that protocols are still evolving and some standards are not yet finished. From a deployment perspective, the lackof standards has slowed progress, but efforts to deploymulticast as an experimental service are in fact gaining momentum. The question nowishow long it will be before multicast becomes a true Internet service. The goal of this paper is to describe the past, present, and future of multicast.

The Core-Assisted Mesh Protocol (CAMP) is introduced for multicast routing in ad-hoc networks. CAMP generalizes the notion of core-based trees introduced for internet multicasting into multicast meshes that have much richer connectivity than trees. A shared multicast mesh is defined for each multicast group; the main goal of using such meshes is to maintain the connectivity of multicast groups even while network routers move frequently. CAMP consists of the maintenance of multicast meshes and loop-free packet forwarding over such meshes. Within the multicast mesh of a group, packets from any source in the group are forwarded along the reverse shortest path to the source, just as in traditional multicast protocols based on source-based trees. CAMP guarantees that, within a finite time, every receiver of a multicast group has a reverse shortest path to each source of the multicast group. Multicast packets for a group are forwarded along the shortest paths from sources to receivers defined within the group's mesh. CAMP uses cores only to limit the traffic needed for a router to join a multicast group; the failure of cores does not stop packet forwarding or the process of maintaining the multicast meshes.

In this paper we investigate the performance of multicast routing protocols in wireless mobile ad hoc networks. An ad hoc network is composed of mobile nodes without the presence of a wired support infrastructure. In this environment, routing/multicasting protocols are faced with the challenge of producing multihop routes under host mobility and bandwidth constraints. In recent years, a number of new multicast protocols of different styles have been proposed for ad hoc networks. However, systematic performance evaluations and comparative analysis of these protocols in a common realistic environment has not yet been performed. In this study, we simulate a set of representative wireless ad hoc multicast protocols and evaluate them in various network scenarios. The relative strengths, weaknesses, and applicability of each multicast protocol to diverse situations are studied and discussed.

Abstract Ad Hoc Networks are gaining popularity as a result of advances in smaller, more versatile and powerful mobile computing devices. The distinguishing feature of these networks is the universal mobility of all hosts. This requires re-engineering of basic network services including reliable multicast communication. This paper considers the special case of highly mobile fast-moving ad hoc networks and argues that, for such networks, traditional multicast approaches are not appropriate. Flooding is suggested as a possible alternative for reliable multicast and simulation results are used to illustrate its effects. The experimental results also demonstrate a rather interesting outcome that even flooding is insufficient for reliable multicast in ad hoc networks when mobility is very high. Some alternative, more persistent variations of flooding are sketched out. Keywords flooding, multicast, ad-hoc networks 1 Introduction Recent advances in portable computing devices and wireless communication technology have made it possible to stay connected anywhere, anytime. In the near future, users will be able to move freely and still have seamless, reliable and high-speed network connectivity. Portable computers and hand-held devices will do for data communication what cellular phones are now doing for voice communication.

This paper presents the On-Demand Multicast Routing Protocol (ODMRP) for wireless mobile ad