We introduce and analyze a scalable re-keying scheme for implementing secure group communications IP multicast. We show that our scheme incurs constant processing, message, and storage overhead for a re-key operation when a single member joins or leaves the group, and logarithmic overhead for bulk simultaneous changes to the group membership. These bounds hold even when group dynamics are not known a-priori.

Abstract Reliable multicast is a powerful communication primitive for structuring distributed programs in which multiple processes must closely cooperate together. In this paper we propose a protocol for supporting reliable multicast in a distributed system that includes mobile hosts and evaluate the performance of our proposal through simulation. We consider a scenario in which mobile hosts communicate with a wired infrastructure by means of wireless technology. Our proposal provides several novel features. The sender of each multicast may select among three increasingly strong delivery ordering guarantees: FIFO, Causal, Total. Movements do not trigger the transmission of any message in the wired network as no notion of hand-off is used. The set of senders and receivers (group) may be dynamic. Size of data structures at mobile hosts, size of message headers, number of messages in the wired network for each multicast, are all independent on the number of group members. The wireless network is assumed to provide only incomplete spatial coverage and message losses could occur even within cells. Movements are not negotiated and a mobile host that leaves a cell may enter any other cell, perhaps after a potentially long disconnection. The simulation results show that the proposed protocol has good performance and good scalability properties. 1

Widespread deployment of multicast depends critically on the existance of congestion control protocols that are provably fair to unicast traffic. In this work, we present an optimization-based congestion control mechanism for one-to-many communication with provable fairness properties. The optimization-based approach attempts to find an allocation of rates that maximizes the aggregate utility of the network. We show that the utility of multicast sessions must be dened in a particular way if a widely accepted property of aggregate utility is to hold. Our definition of session utility amounts to maximizing a weighted sum of simple utility functions, with weights determined by the number of receivers. The fairness properties of the optimal rate allocation depend both on the weights and form of utility function used. We show that although it is not strictly fair to unicast, the unfairness of our mechanism is bounded and can be controlled.

Desirable features of reliable multicast include low end-to-end delays, high throughput and scalability, and meeting these objectives is not an easy task. We propose a receiverbased (replier) local recovery multicast protocol with dynamic repliers elected on a per-packet basis. Designed to provide an efficient reliable multicast service without any cache facilities in the multicast tree, our approach, noted DyRAM, uses low-overhead active services in routers. After presenting the protocol and some designed and implementation issues the paper compares DyRAM to ARM, the nearest active reliable multicast protocol in term of functionalities proposed in the active multicast community. Simulation results show that DyRAM performs much better than an ARM-like protocol which needs a significant amount of cache to exhibit performances. Additionally, in case some cache is available for DyRAM and ARM, the study shows that DyRAM always performs better than ARM.

We propose an end-to-end single-rate source-based multicast congestion control scheme (LE-SBCC) for reliable or unreliable multicast transport protocols. It addresses key issues such as drop-to-zero issues [27], TCP friendliness [1] and RTT estimation. The scheme consists of a cascaded set of filters and a rate adaptation policy module (AIMD or TFRC [9]) which transform the multicast tree to appear like a unicast path for the purposes of congestion control. The scheme is not self-clocked but acts upon a stream of loss indications (LIs), which are filtered to get a stream of loss events (LEs) [9] (at most one per RTT per receiver). This LE stream is further filtered to extract the maximum LEs from any one receiver, which results in at most one rate-reduction per RTT. A range of results (simulation and experimental) is presented and compared against the mathematical model of the scheme components.

This document gives an overview of most of the directions taken by research in the multicast area. We first introduce the basic concepts. The following sections deal with high level services that can (or must) be provided on top of the underlying multicast routing infrastructure. Then we consider new evolutions in multicast routing: new protocols, their large scale deployment, and future trends. Finally we discuss multicast tools and applications.

Many works have recently addressed the issue of congestion control for multicast communications and the problem is known to be highly complex. Scalability, responsiveness, stability and fairness with TCP are some of the required properties. In this paper, we present a congestion avoidance scheme for bulk data distribution called AMCA (Active-based Multicast Congestion Avoidance algorithm) that tries to meet these properties. We use the active networking technology to perform on a per-section dialogue to probe for available bandwidth along a multicast tree. The solution uses the RTT variations experienced by every branch to estimate the congestion situation in the multicast tree. The physical multicast tree is also used to appropriately aggregate the RTT variations at intermediate nodes before they reach the source. Simulations show that AMCA converges, makes use of the available bandwidth and reacts rapidly to dynamic changes while being TCP-fair.

most critical yet challenging technologies to meet the exponentially growing demands for data distribution in a large variety of applications of the Internet (grid computing, web applications, distributed simulations. . . ). When reliability is required, there is no straightforward solutions and meeting the objectives of reliable multicast is not an easy task. Active networks open a new perspective in providing more efficient solutions for the problem of the reliability. In this context, routers are able to perform customized computations on the messages flowing through them. In this paper, we propose a new active service which consists in a loss detection service to be deployed into routers. We also show how the loss detection service can improve the performances of the DyRAM active reliable multicast protocol in term of the recovery delays making DyRAM suitable for applications requiring low latencies.

Associating customized processing to incoming packets, active networking provides a general framework for new protocol deployment and new service implementations. Recently, the use of these active network concepts has been proposed in many research areas including multicast protocols where efficient mechanisms to the reliability problems can be proposed. However, these active services introduce additional processing costs that must be carefully evaluated. This paper presents the preliminary results in measuring, in the context of the DyRAM protocol, the raw processing time required for enabling low-latency multicast communications on the Internet.

Reliable multicast protocols have gained popularity with active service contributions where routers implement additional functionalities. Reducing the delay of recovery is one of the desirable features of a reliable multicast protocol. In this paper we propose an active-based architecture with specialized routers. Using simulations we show how this architecture with the proposed services (mainly the loss recovery from the receivers and the loss detection at the routers), could improve the performances of a reliable multicast application in term of the recovery delay.