Active resource allocation for active reliable multicast

Packet loss recovery is a key issue in reliable multicast. An effective way for packet loss recovery is to place repair servers with active routers along the transmission paths. These repair servers naturally form a hierarchical cache system due to the hierarchical nature of the multicast tree. How to design an effective hierarchical cache system to minimize the packet loss is important. In this paper, we first derive a cooperative caching efficiency model for a hierarchical cache system. Based on the model, a heuristic Cooperative Cache Replacement (CCR) algorithm is proposed to achieve efficient cache performance for reliable multicast systems. The implementation issues are also discussed in detail. The ns-2 based simulations are conducted to evaluate the performance of the proposed algorithm by compared to the optimal caching time (OCT) based algorithm. The results show that CCR effectively reduces the packet loss recovery latency.

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.

Scalability is of paramount importance in the design of reliable multicast transport protocols, and requires careful consideration of a number of problems such as feedback implosion, retransmission scoping, distributed loss recovery, and congestion control. In this article, we present a reliable multicast architecture that invokes active services at strategic locations inside the network to comprehensively address these challenges. Active services provide the ability to quickly and efficiently recover from loss at the point of loss. They also exploit the physical hierarchy for feedback aggregation and effective retransmission scoping with minimal router support. We present two protocols, one for packet loss recovery and another for congestion control, and describe an experimental testbed where these have been implemented. Analytical and experimental results are used to demonstrate that the active services architecture improves resource usage, reduces latency for loss recovery, and provides TCP-friendly congestion control.

This paper presents a case study in implementing a moderately complex, useful service on an active network platform. The active application is reliable multicast with congestion control; the platform comprises the Bowman Node Operating System and the Composable Active Network Elements (CANEs) Execution Environment. The importance of the work stems from the lessons it provides about the design and implementation of active platforms in general and Bowman/CANEs in particular. For example, our experience shows that timer-driven active node processing is as important as packet-arrival-driven processing. Thus, execution environments cannot focus exclusively on forwarding, but must also provide efficient timers and allow timer handlers the same capabilities as packet-driven computations. Other areas in which the implementation provides insight include service decomposition approaches for active applications and information sharing among service components.

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.

In reliable multicast, data packets can be cached at some nodes such as repair servers for future possible retransmission in loss recovery schemes. How to cache packets to optimize the performance of loss recovery is an important issue in reliable multicast protocol design. In this paper, we present a general solution which addresses the main design problems of caching policies. We first formulate the caching policy design as an optimization problem by employing caching utility as a uniform measure. Based on caching utility, we propose an algorithm called Optimal Caching Time (OCT) for configuring the caching time of packets and demonstrate that it solves the optimization problem. Furthermore, we analyze the performance improvement of OCT caching policy compared to the existing caching policies such as FIFO, Probabilistic FIFO (P-FIFO), and Timer-Based Caching Policy (TBCP). We use ns-2 simulations to demonstrate the performance gains brought by OCT caching policy. The numerical results show that OCT caching policy improves the performance significantly, especially for heterogeneous groups of receivers. With the inherent generality of the proposed model and the OCT algorithm, they can be easily applied to the general cache design in reliable unicast or multicast applications, and in both wired and wireless networks.

Multicasting plays an important role in internet networks. Supporting wavelength division multiplexed (WDM) multicasting in an IP over WDM network poses interesting problems because some WDM switches may be incapable of switching an incoming signal to more than one output interface. Although some multicast applications, such as audio/video conferencing can tolerate packet error or loss, other applications such as one-to-many file transfer and military applications do not. Hence, an inevitable need for reliable multicasting arises. The reliable multicast protocol ensures the eventual delivery of multicast data to all multicast group members. The reliable multicast is receiver initiated NACK-based and it makes use of feedback suppression in order to avoid NACK and retransmission implosion. The loss recovery burden is distributed over the multicast group members in order to reduce recovery latency and end-to-end delay. The proposed protocol is evaluated in terms of performance metrics for an IP/WDM optical network which will be the candidate for the next generation internet 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 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.

We present the router-assisted error control model (RRMEC), which takes advantage of the location and knowledge of the topology of routers to build a logical tree, and uses the repair host associated with the routers to buffer the data packet and perform retransmission recovery tasks. This model can establish a hierarchy being congruent with the multicast distribution tree and solve the major problem on reliable multicast efficiently. This paper gives the implementation of a prototype in active network, i.e., ANRM. The ANRM can provide an efficient method for rapid update and deployment of reliable multicast protocol.

Building on the success of unicast IP, IP Multicast adopted a simple, open, best-effort delivery model with many-to-many semantics. Despite several years of effort, a general, scalable and reliable end-to-end transport protocol analogous to TCP has proven elusive. Proposed solutions are either inflexible, or incur high control overhead. We present Lightweight Multicast Services (LMS), which enhance the IP Multicast model with simple forwarding services to facilitate scalable and efficient (compared to pure end-to-end) solutions to problems such as reliable multicast. In LMS, routers tag and steer control packets to preselected endpoints and perform fine-grain multicast to guide responses to a subset of the group without transport-level processing. LMS divides error control into transport and forwarding components, which allows the former to remain at the end-points while the latter is pushed to the routers, where it can be implemented very efficiently. The division is clean, resulting in significant gains in performance and scalability, while reducing application complexity. LMS reaches beyond reliable multicast to applications such as scalable collect, any-cast, and in general, any application that can benefit from a hierarchy congruent with the underlying topology.

The explosive growth of the Internet demands higher reliability and performance than what the current networking infrastructure can provide. This dissertation explores novel architectures and protocols that provide a methodology for grouping together multiple networking elements, such as routers, gateways, and switches, to create a more reliable and performant distributed networking system. Clustering of networking elements is a novel concept that requires the invention of distributed computing protocols that facilitate efficient and robust support of networking protocols. We introduce the Raincore protocol architecture that achieves these goals by bridging the fields of computer networks and distributed systems. In designing Raincore, we paid special attention to the unique requirements from the networking environment. First, networking clusters need to scale up the networking throughput in addition to the scaling up of computing power. Second, task switching between the different services supported by a networking element has a major negative impact on performance. Third, fast fail-over time is critical for maintaining network connections in the event of failures. We discuss in depth the design of Raincore Group Communication Manager that addresses the forgoing requirements and provides group membership management and reliable multicast transport. It is based on a novel token-ring protocol. We prove that this protocol is formally correct, namely, it satisfies the set of formal specifications that defines the Group Membership problem. The creation of Raincore has already made a substantial impact both at Caltech and the academic community as well as in the industry. The first application is SNOW, a scalable web server cluster that is part of RAIN, a collaborative project between Caltech and JPL/NASA. The second application is RainWall, a commercial solution created by Rainfinity, a Caltech spin-off company, that provides the first fault-tolerant and scalable firewall cluster. These applications exhibit the fast fail-over response, low overhead, and near-linear scalability of the Raincore protocols. In addition, we studied fault-tolerant networking architectures. In particular, we considered efficient constructions of extra-stage fault-tolerant Multistage Interconnection Networks. Multistage Interconnection Networks provide a way to construct a larger switching network using smaller switching elements. We discovered an optimal family of constructions, in the sense that it requires the least number of extra components to tolerate multiple switching element failures. We prove that this is the only family of constructions that has this optimal fault-tolerance property.

Building a network embedded FEC protocol by using game theory

A Cooperative Reliable Multicast Protocol (CRMP) has been developed to improve real-time data transmission onthe Internet Multicast Backbone (MBone) by adding a retransmit server and some repair servers to the multicastsession in order to recover lost packets. This paper describes a design and implementation of CRMP with Localrecovery (L-CRMP), an extension to the original CRMP. In L-CRMP, each repair server can work as a local serverthat retransmits packets to other repair servers that do not receive them from the source. Our goal in L-CRMP is toreduce the network overhead caused by retransmission packets while keeping the effective loss rate at the receiversapproximately the same.Keywords: MBone, Reliable Multicast, Local recovery 1. INTRODUCTION Real-time multicast applications are transmitted over the Internet through MBone (Multicast Backbone), a logicalnetwork running on top of the IP layer.1'2 Many of them, such as vat (Visual Audio Tool) or nv (Network Video),are based on RTP (Real-time Protocol) that does not support reliability. These applications may often experiencepoor quality due to large packet loss.3'4 A protocol, Cooperative Reliable Multicast Protocol (CRMP), is proposedin reference5 to alleviate the problem. A unique feature of CRMP is that it can be used with the current MBoneapplications without changing the operation of the source or receivers. Receivers that participate in CRMP coexistwith those that do not, but enjoys a better quality.Most reliable multicast protocols are designed for data transmission which requires perfect reliability but isresilient to delay, e.g.,6'7 and references therein. CRMP is however designed for real-time applications and exploitsthe fact that they do not require perfect reliability and, due to their stream nature, do not need acknowledgementfor every packet. In a large heterogeneous network, the delay between the retransmit server and some of the repairservers may be excessive. This motivates our extension of the original CRMP to include local recovery. It exploitsthe fact that loss at different repair servers is not synchronized, and therefore, a retransmission request of a repairserver may be fulfilled by a nearby repair server that has received the packet. In this paper we present a designand implementation of CRMP with local recovery (L—CRMP), and evaluate its performance. In addition to local

Active networks are a promising way to develop new services for data transport, but active routers could also store "on the fly" streams of data for high level services such as Web cache and reliable multicast. In this paper we describe the merging of active networking with distributed storage solutions. We focus our approach on two dedicated frameworks : the IBP suite and the Tamanoir execution environment. We describe the overall architecture of the Active Logistical Storage suite and present first experimental results.