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.

Designing an interdomain multicast routing scheme that makes efficient use of network resources while delivering good performance to applications is a significant challenge. A variety of schemes have been proposed, but little has been done to compare the schemes systematically over a rich set scenarios. In this work we develop a framework to do systematic evaluation of multicast routing schemes, and apply it to two practical schemes: Distance Vector Multicast Routing Procotol and Core Based Trees. We conclude that Core Based Trees has the potential to make more efficient use of resources, with modest performance penalty. However, this requires mechanisms to choose good cores. We suggest a heuristic for evaluating the goodness of a core and moving towards a good core. College of Computing Georgia Institute of Technology Atlanta, Georgia 30332--0280 1 Introduction There is little question that emerging networking applications will require multicast capability. From video conferencing ...

In this paper, we study the problem of multicast routing on directed graphs. We de ne the asymmetry of a graph to be the maximum ratio of weights on opposite directed edges between a pair of nodes for all node-pairs. We examine three types of problems according the membership behavior: (i) the static, (ii) the join-only, (iii) the join-leave problems. We study the eect of the asymmetry on the worst case performance of two algorithms: the Greedy and Shortest Paths algorithms. The worst case performance of Shortest Paths is poor, but it is aected by neither the asymmetry nor the membership behavior. In contrast, the worst case performance of Greedy is a proportional to the asymmetry in a some cases. We prove an interesting result for the join-only problem: the Greedy algorithm has near-optimal on-line performance.

In this paper, we investigate a state dependent multicast routing algorithm called Least Load Multicast Routing (LLMR), for single rate loss networks. The algorithm is based on Least Load Routing (LLR) concept and the approach is to select the least load links for establishing connections. To facilitate tractable analysis, the networks considered are assumed symmetrical and fully connected. In addition, connection requests are Poisson arrival and the holding times of accepted calls are exponentially distributed. We combine one-time simulations and fixed point equation (FPE) to develop an analytical model for LLMR. Analytical results are compared with simulation results and the agreement is surprisingly good. We find that the effect of link independence assumption is insignificant for the analytical model. 1 Introduction Multicasting refers to the ability of a set of more than two nodes or end-users in a com- This research was supported in part by Hongkong Telecom Institute of Infor...

nt and migration. At the application layer, the existence of network multicast does not guarantee that an application can take advantage of it. We demonstrate the adaptation of a traditionally unicast application -- database sharing -- to multicast, thus achieving scaling in network and processor performance. For the transport layer, there is a growing consensus in the research community that relying on generic protocols can significantly reduce the efficiency of many applications. This effect seems to be even more pronounced for multicast transport protocols; consequently, protocols may need to be constructed for different types of applications iii to achieve increased efficiency. We propose a reliable multicast transport protocol tuned specifically for bulk-data applications, such as our multicast-adapted database sharing application. In developing this new transport protocol, we employ a synergy of new and existing techniques in multicast transport. We propose a new sender s

This work studies the problem of multicast routing both at a theoretical and a practical level. Multicasting involves the distribution of the same data to several receivers at the same time. Ecient multicast routing can reduce the communications cost of the distribution tree. In this document, we extend and study the most widely used routing algorithms in a variety of problems, and we compare their performance theoretically and through simulations. First, we study how the asymmetry of directed networks and the membership behavior aect the performance of these algorithms. We prove bounds for the various cases of these problems in a worst case analysis. Second, we propose algorithms for multicast connections where the users have dierent quality expectations from the multicast connection. We prove bounds for the performance of our algorithms, and examine their performance in a variety of scenarios through simulations. Third, we propose, QoSMIC, a multicast protocol for the Internet. A major advantage of QoSMIC is that the routing decisions consider the quality requirements of the users. In addition, the protocol limits the role of pre-con guration decisions, which cause problems in the employment of some previous protocols. Another important feature of the protocol is its exibility; it can scale to large networks, and it can adapt and evolve with the needs of the applications and the requirements of the users.

Asynchronous Transfer Mode (ATM) network technology is expected to become a central part of the emerging global information infrastructure. ATM networks introduce a number of features that distinguish them from earlier technologies and introduce new issues in network control. This paper offers a framework for precisely defining and analyzing alternative approaches to the distributed control of ATM networks and explores some of the key design issues through a series of examples. It is hoped that it will provide a useful foundation for researchers in networking and distributed computing interested in exploring these issues further and developing more complete solutions.

We present, QoSMIC, a multicast protocol for the Internet that supports QoS-sensitive routing, and minimizes the importance of a priori configuration decisions (such as core selection). The protocol is resourceefficient, robust, flexible, and scalable. In addition, our protocol is provably loop-free. Our protocol starts with a resources-saving tree (Shared Tree) and individual receivers switch to a QoScompetitive tree (Source-Based Tree) when necessary. In both trees, the new destination is able to choose the most promising among several paths. An innovation is that we use dynamic routing information without relying on a link state exchange protocol to provide it. Our protocol limits the effect of pre-configuration decisions drastically, by separating the management from the data transfer functions; administrative routers are not necessarily part of the tree. This separation increases the robustness, and flexibility of the protocol. Furthermore, QoSMIC is able to adapt dynamically to the conditions of the network. The QoSMIC protocol introduces several new ideas that make it more flexible than other protocols proposed to date. In fact, many of the other protocols, (such as YAM, PIM-SM, BGMP, CBT) can be seen as special cases of QoSMIC. The goal of this document is to present the motivation behind, and the design of QoSMIC, and to provide both analytical and experimental results to support our claims.

Cooperative multimedia applications like desktop conferencing and joint design, involving a group of distributed users, are best build upon a multicast communication service. All of the currently discussed multicast protocols are based on the assumption of a connectionless, packet switched network layer. Since such networks do not guarantee the quality of service requirements of distributed multimedia applications, performance trade-offs have to be considered carefully. In this paper we present performance studies of connectionless network layer multicast protocols with best-efforts delivery semantics. Performance results derived from measurements and simulations will be discussed. The simulations are based upon an OPNET model of a multicast architecture and cover comparisons between true and emulated multicast packet delivery in a real-time video conferencing scenario. 1 Introduction Cooperative multimedia applications like desktop conferencing and joint design, involving a group of...

The increasing demand for point-to-multipoint connections has established multicast routing as a crucial aspect of network management. Hierarchical encoding is a newly proposed technique that offers a variety of quality levels in one encoding; a user or a switch can filter the data that will be processed further. In this paper, we examine how hierarchical encoding can increase the efficiency of multicast routing and propose polynomial algorithms to this effect. Theoretical and experimental work demonstrates the advantage of the proposed algorithms over previous solutions. 1 Introduction Multicasting can be defined as the distribution of the same information stream from one to many nodes concurrently. A lot of emerging applications are of multicast nature, and thus multicasting has become an important research area. The main idea is that instead of multiple point-to-point connections it is more efficient to distribute the information on a tree. Efficiency is directly related to network...