Light-Weight Multicast Services (LMS): A Router-Assisted Scheme for Reliable Multicast

In multihop wireless networks, many applications require end-to-end reliable multicast communication with 100% packet delivery ratio. Recently, network coding has been applied to the reliable link-level multicast in wireless networks, where multiple lost packets with distinct intended receivers are XOR-ed together as one packet and forwarded via single retransmission, resulting in a significant reduction of bandwidth consumption in the scenarios of many receivers. However, the simple XOR operation cannot fully exploit the potential coding opportunities. Moreover, for the reliable multicast in multihop wireless networks, the number of receivers of link-level multicast is usually not large and thus this coding-based link-level multicast cannot provide a promising gain. In this work, we propose a new network coding-based reliable multicast scheme which exploits both network coding and the physical-layer broadcast nature. Specifically, first, at each link-level multicast the source node performs the more general coding operations instead of XOR and conducts the random linear packet coding such that more coding gain can be achieved. Second, each node snoops on all communications over the wireless medium and stores the overheard packets for packet decoding, such that an additional coding gain can be obtained. Extensive simulations demonstrate that the proposed scheme can greatly improve the transmission efficiency, especially in the case of large-group multicast.

OMG has published an unreliable multicast specification for distributed applications developed in CORBA (UMIOP). This mechanism can be implemented based on IP Multicast, a best-effort protocol, which provides no guarantees about the message delivery. However, many fault-tolerant or groupware applications demand more restrictive agreement and ordering guarantees (for instance, reliable multicast with FIFO, causal or total ordering) from the available support for group communication. OMG has not yet provided any specification for supporting those requirements. This paper presents an important contribution towards this direction. We proposed the ReMIOP, an extension to the UMIOP/OMG protocol, for the conception of a reliable multicast mechanism in CORBA middleware. Performance measures comparing ReMIOP, UMIOP and UDP sockets for IP multicast communication are presented in order to evidence the costs for adding reliable and unreliable multicast in middleware level.

The practical use of IP multicast is starting on the Internet with the development of many reliable multicasts in recent years, and it is supposed that IP multicast will spread rapidly in the near future. At that time, congestion of multiple multicast traffics will occur in a certain network. But the service quality in such a case has not been made clear. Then, we evaluated the reliability of multicast traffic under the congestion of multiple multicast traffics including reliable multicast traffic using an experimental network. In this paper, we present the evaluation results of the experiment, and propose a reliability control scheme applied with QoS technique for improving reliability.

IP multicast plays a very important role in group communication. At the network level IP multicast provides an efficient one-to-many IP packets delivery but without providing any reliability guarantees. Desirable features of reliable multicast include low end-to-end delay, high throughput and scalability. Active networks open a new perspective in providing more efficient solutions to the problems of reliability. However, the existing active reliable multicast protocols are based on receiver-initiated approach for loss recovery. In this paper we propose a new active reliable multicast protocol by combining sender- initiated and receiver-initiated approaches for loss recovery. This approach helps to solve the scalability problems like acknowledgement implosion, recovery load balancing etc.

This document generally describes how to use Forward Error Correction (FEC) codes to efficiently provide and/or augment reliability for data transport. primary focus of this document is the application of FEC codes to one-to-many reliable data transport using IP multicast. This document describes what information is needed to identify a specific FEC code, what information needs to be communicated out-of-band to use the FEC code, and what information is needed in data packets to identify the encoding symbols they carry. procedures for specifying FEC codes and registering them with the Internet Assigned Numbers Authority (IANA) are also described. This document should be read in conjunction with and uses the terminology of the companion document titled, The Use of Forward Error Correction (FEC) in Reliable Multicast.

Local loss recovery for reliable multicast can provide significant performance improvement in terms of loss recovery latency, bandwidth consumption and network throughput. Active reliable multicast (ARM) is a novel loss recovery scheme for large-scale reliable multicast. When sufficient active resources of active routers (ARs) and associated cache are available, ARM gives good loss recovery latency performance. The authors build an analytical model for studying the optimal active resource allocation for ARM. They propose a top-down layering analysis (TDLA) approach to derive the expected loss recovery latency (ELRL). For a given multicast tree, the ELRL is derived as a function of the active resource allocation pattern. Simulation experiments reveal that high performance gains can be attained with limited active resources, which are properly allocated. It is also shown that simulation results have a good match with the analytical results. The analytical framework developed can be used for further investigation of various active resource allocation schemes and caching policies.

We present MTCT, a congestion control scheme for large-scale reliable multicast. Congestion control for reliable multicast is important because of its wide applications in multimedia and collaborative computing, yet nontrivial, because of the potentially large number of receivers involved. Many schemes have been proposed to handle the recovery of lost packets in a scalable manner; but there is little work on the design and implementation of congestion control schemes for reliable multicast. We propose new techniques that can effectively handle instances of congestion occurring simultaneously at various parts of a multicast tree. Our protocol incorporates several novel features: (1) hierarchical congestion status reports that distribute the load of processing feedback from all receivers across the multicast group, (2) the relative time delay (RTD) concept which overcomes the difficulty of estimating round-trip times in tree-based multicast environments, (3) window-based control that prevents the sender from transmitting faster than packets leave the bottleneck link an the multicast path through which the sender's traffic flows, (4) a retransmission window that regulates the flow of repair packets to prevent local recovery from causing congestion, and (5) a selective acknowledgment scheme that prevents independent (i.e., non-congestion-related) packet loss from reducing the sender's transmission rate. We have implemented MTCP both on UDP in SunOS 5.6 and on the simulator ns, and we have conducted extensive Internet experiments and simulation to test the scalability and inter-fairness properties of the protocol. The encouraging results we have obtained support our confidence that TCP-like congestion control for large-scale reliable multicast is within our grasp.

RelM: reliable multicast for mobile networks

An attempt is made to realize highly reliable multicast communications without modifying the TCP protocol, which is now the most widely used in the Internet, and TCP multicast using a GRA (generic router assist) router is proposed. The characteristics of this multicast communications are evaluated, and it is shown that the overall throughput of multicast communications is governed by the bottleneck link in the transmission band. An attempt is made to improve the performance of multicast communications with a bottleneck link, and an environment‐adaptive multicast communication scheme is proposed, in which the multicast tree is partitioned at the bottleneck link, and TCP multicasting is performed for each subtree. Performance evaluation by simulation shows that the proposed method alleviates the effect of the bottleneck link on the overall multicast and that the performance of the multicast as a whole can be improved. © 2003 Wiley Periodicals, Inc. Electron Comm Jpn Pt 1, 87(3): 28–38, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ecja.10161

We report the design, implementation and evaluation of Merged Hybrid ARQ with staggered FEC (MHARQ) system for video multicast over wireless LANs. MHARQ combines the advantages of receiver-driven staggered FEC and hybrid ARQ schemes to compensate the large dynamic range of WLAN channels and to achieve high reliability, scalability and wireless bandwidth efficiency for video multicast. The FEC packets generated by a cross-packet FEC code are divided into multiple streams according to the pre-configured overhead and are transmitted in different multiple IP multicast groups. Certain FEC streams are delayed from the original video stream. The receivers dynamically join/leave the FEC multicast groups based on the channel conditions. For efficient utilization of WLAN bandwidth, FEC data for a multicast group would not be transmitted by the APs in wireless networks if no receiver joins this group. The time shift between the video stream and the FEC streams introduces temporal diversity and compensates for the client join delay and handoff interruption. In addition, when delayed FEC packets are not enough to recover the lost packets, the receivers can send a hybrid ARQ request to the video server. We design a channel estimation algorithm for a receiver to dynamically determine the delayed FEC multicast groups to join and/or send ARQ NACK to request for retransmission. Using the ORBIT radio grid testbed, we have investigated the performance of the proposed MHARQ system with various numbers of users per AP and different number of APs per video server. It is demonstrated via real system implementation on ORBIT that MHARQ improves wireless bandwidth efficiency and scalability for reliable video multicast, compared with existing reliable multicast schemes.

Although IP multicast has been rapidly evolving in the last few years, the current Internet is not fully multicast-enabled because of the lack of robust inter-domain routing and controlling protocols. In this paper, we present an alternative architecture for data distribution on Internet called PSRM that realizes semantic reliable, loose synchronized, multicast data delivery. PSRM is not based on global IP multicast, instead it uses a hybrid way to combine unicast delivery with multicast delivery. In PSRM, IP multicast is used only in local area, or multicast domain, to enhance the performance, and these multicast domains are organized into a spanning tree by TCP connections. As PSRM is based upon ALF protocol architecture, we use application-defined semantics to adapt content in a heterogeneous environment. PSRM have been implemented and demonstrated by a prototype distance learning application.

On performance of group key distribution techniques when applied to IPTV services

Without doubt, multicast communication as a means for one-to-many or many-to-many delivery of data has become a hot topic in multimedia environments. A lot of people are interested in multicast: the research community, standards groups and Internet Service Providers (ISP) among them. Although IP multicast is a very good solution for Internetworking multimedia in many-to-many communications, there are still issues that have not been completely solved. Protocols are still evolving and new protocols are constantly coming up to solve these issues because that is the only way for making multicast become a true Internet service. The main goal of this chapter is to describe the evolution of IP multicast from the obsolete MBone (Multicast Backbone) and intra-domain multicast routing to the actual inter-domain multicast routing scheme. We will pay special attention to the challenges and problems that need to be solved, the problems that have been solved and the way they were solved. We will make a complete picture of the state of the art explaining the idea behind each protocol and how all those protocols work together.

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.

Multicast communication is a topic of intense study by the network research community. The IP Multicast service of the network layer doesn't provide the desired reliability to some multicast applications, and the interest towards approaches to reliable multicast communication has increased. In this work, we focus on the Server Replication method, wherein the data are replicated over a subset of the multicast-capable relaying hosts and retransmission requests from receivers are handled by the nearest Replicated Server. The problem of selecting the best subset of the multicast-capable relaying hosts to replicate the data is NP-Hard. We propose a hybrid metaheuristic to find near optimal solutions for this problem. This proposal is based on a hybrid version of the GRASP metaheuristic that incorporates data mining techniques. Experimental results show that our technique outperforms existing approaches.