FIFO based multicast scheduling algorithm for VOQ packet switches

In this paper, we consider scheduling in multicast switching networks, which aims to minimize the multicast latency for a set of multicast requests. Such a problem has been proved to be NP-complete. We propose a simple, fast greedy multicast scheduling algorithm and derive a lower bound and an upper bound on the performance of the algorithm. As can be seen, while a lower bound is fairly straightforward, the upper bound is much more difficult to obtain. By translating the multicast scheduling problem into a graph theory problem and employing a random graph approach, we are able to obtain a probabilistic upper bound on the performance of the multicast scheduling algorithm. Our analytical and simulation results show that the performance of the proposed multicast scheduling algorithm is quite close to the lower bound and is statistically guaranteed by the probabilistic upper bound.

Studies issues of multicasting in multistage interconnection networks (MINs) for large-scale multicomputers. In addition to point-to-point communication among the processing nodes, efficient collective communication is critical to the performance of multicomputers. This paper presents a new approach to support multicast communication, on the basis of a restricted address encoding scheme which constructs a short fixed-size multicast header, and a recursive scheme that recycles a multicast packet one or more times through the network to send it to the desire destination nodes. We propose a novel deadlock-free multicast algorithm for multiple multicast packets in MIN-based multicomputers. We also present a performance model for the unbuffered MIN using the multicast algorithm and analyze its performance in terms of the network throughput, where several multicast communications are considered.

This paper proposes a new reservation-based multicast scheduling algorithm which tries to make use of every data slot on all data channels such that the performance of the system is improved.

Summary form only given. Multicast communication, which involves transmitting information from one node to multiple nodes, is a vital operation in both broadband integrated services digital networks (BISDN) and scalable parallel computers. Among different multicast switching networks, much work has been centered around the crossbar switches due to the simplicity of implementation. However, crossbars have the maximum number of crosspoints and implementation complexity among all switching fabrics. Multistage interconnect networks (MINs) such as Clos networks have attracted many attentions in recent years due to the nonblocking property as the crossbars, while at the same time possessing many advantages over crossbars. However, no multicast scheduling and routing algorithm have been applied to Clos network. This paper explores this aspect - we study some existing multicast scheduling and routing algorithms and apply them to Clos networks. Moreover, we propose two packet scheduling strategies to improve the system performance in terms of switch blocking probability and throughput, as shown by simulations.

<para xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> We propose a cross-layer design for resource-constrained systems that simultaneously decode multiple video streams on multiple parallel processors, cores, or processing elements. Our proposed design explicitly considers the coder specific application characteristics such as the decoding dependencies, decoding deadlines, and distortion impacts of different video packets (e.g., frames, slices, groups of slices etc.). The key to the cross-layer design is the resource management control plane (RMCP) that coordinates the scheduling and processor selection across the active applications. The RMCP deploys a priority-queuing model that can evaluate the system congestion and predict the total expected video quality for the set of active decoding tasks. Using this model, we develop a robust distortion- and delay-aware scheduling algorithm for video packets. This algorithm aims to maximize the sum of achieved video qualities over all of the decoded video sequences. Additionally, we propose a processor selection scheme intended to minimize the delays experienced by the queued video packets. In this way, the number of missed decoding deadlines is reduced and the overall decoded video quality is increased. We compare queuing-theoretic based scheduling strategies to media agnostic scheduling strategies (i.e., earliest-deadline-first scheduling) that do not jointly consider the decoding deadlines and distortion impacts. Our results illustrate that by directly considering the video application's properties in the design of a video decoding system, significant system performance gains on the order of 4 dB peak-signal-to-noise ratio can be achieved. </para>

Multi-chip scheduler implementation in IQ switches are suited to reduce the hardware complexity in very large, high-speed, switches. However, this implies introducing a RTTs (Round Trip Time) among input and output selectors used to determine a matching due to inter-chip latency. This delay requires modifications to scheduling algorithms to allow a fully distributed implementation while keeping good performance. We propose a novel multicast scheduler, named IMRR, an extension of a previously proposed multicast scheduling algorithm named mRRM, making it suitable to a multi-chip implementation, and examine its performance by simulation.

Layered multicast is a scalable solution to data dissemination in heterogeneous networks such as the Internet. In this paper, we study the scheduling problem arising in the layered multicast context. Our goal is to generate a multicast schedule for two different objectives, i.e., to minimize the weighted sum (the L 1 objective) of the per-layer average waiting time, and to minimize the maximum approximation ratio (the L ∞ objective) of the subschedules on individual layers. Compared to the previous work on multicast scheduling, this paper addresses the data popularity and the interaction among layers simultaneously. We present a simple randomized algorithm for both objectives of the layered multicast scheduling problem. For the L 1 objective, we provide a deterministic 2-approximation algorithm for the general multi-layer cases. For the L ∞ objective, we present an algorithm for the two-layer case which is 1.6875-approximation ignoring an additive constant.

Recent developments in networking technologies, coupled with the advent of high-capacity storage devices and improved coding schemes, will make it feasible to provide many advanced multimedia communications services. Among future telecommunication services, the VOD (Video On Demand) service is emerging as one of the most promising services. In this paper, we propose a new VOD service scheme that utilizes the dynamic multicasting capabilities of future networks. We first describe an overall VOD service architecture that consists of CPEs (Customer Premise Equipments), SCCs (Service Control Centers), and ISs (Information Stores). Based on the assumptions that each subscriber has local storage space and the video transfer speed is faster than the playback speed, we develop a new service scheme where video signals are multicasted to multiple subscribers simultaneously. To realize the potential benefits of multicasting, we propose two scheduling algorithms: EDS (Earliest Deadline Scheduling) and MMS (Most Multicasting Scheduling). Finally, we study the performance of multicasting scheme and compare the performance of the two scheduling algorithms via computer simulation. The simulation results show that multicasting increases the service capacity of an SCC significantly.

We address the multicast problem in a wireless multihop network in the presence of errors. Finding the multicast schedule that minimizes the expected number of transmissions, while accounting for both the wireless broadcast advantage (WBA) and the wireless unreliable transmission (WUT) characteristics, has not been solved optimally before. We formally define the problem and propose an initial algorithm of non-polynomial complexity to obtain the optimal solution. The algorithm starts by transforming the wireless network topology into an auxiliary expanded graph that captures the WBA property, and assigning appropriate weights to the links so as to capture the WUT property. The proposed transformation is interesting on its own merit, since it permits us to consider only point-to-point transmissions (as in wireline networks) in the expanded graph, instead of the point-to-multipoint transmissions present in the original wireless network, and can also be useful in other optimization problems some of which we briefly describe. By solving the minimum Steiner tree problem on the expanded graph we obtain the optimal multicast solution for the initial graph. Since the optimal algorithm is of non-polynomial complexity, we also propose a number of heuristic algorithms. In particular, we first present a truncated graph transformation and then describe two heuristic algorithms for obtaining the multicast schedule. Simulation results show that the proposed heuristics have performance close to that of the optimal algorithm, at least for the instances for which we were able to track optimal solutions, while outperforming other heuristic multicast algorithms.

High-speed routers and high-performance data centers share a common system-level architecture in which multiple processing nodes are connected by an interconnection network for high-speed communications. Load balancing is an important technique for maximizing throughput and minimizing delay of the interconnection network. In this thesis, efficient load balancing schemes are designed and analyzed for next-generation routers and data centers.&#13;\n&#13;\nIn high-speed router design, two preferred switch architectures are input-queued switch and load-balanced switch. In an input-queued switch, time-domain load balancing can be carried out by an iterative algorithm that schedules packets for sending in different time slots. The complexity of an iterative algorithm increases rapidly with the number of scheduling iterations. To address this problem, a single-iteration scheduling algorithm called D-LQF is designed, in which exhaustive service policy is adopted for reusing the matched input-output pairs in the previous time slots to grow the match size. &#13;\n&#13;\nUnlike an input-queued switch, a load-balanced switch consists of two stages of crossbar switch fabrics, where load balancing is carried out in both time and space domains. Among various load-balanced switches, the feedback-based switch gives the best delay-throughput performance. In this thesis, the feedback-based switch is enhanced in three aspects. Firstly, we focus on reducing its switch fabric complexity. Instead of using crossbars, a dual-banyan network is proposed. The complexity of dual-banyan can be further reduced by merging the two banyans to form a Clos network, resulting in a Clos-banyan network. Secondly, we target at improving the delay performance of the feedback-based switch. A Clos-feedback switch architecture is devised where each switch module in the Clos network is a small feedback-based switch. With application-flow based load balancing, packet order is ensured and the average packet delay is reduced from O(N) to O(n), where N and n are the switch and switch module sizes, respectively. Thirdly, we extend the feedback-based switch to support multicast traffic. Based on the notion of pointer-based multicast VOQ, an efficient multicast scheduling algorithm with packet replication at the middle-stage ports only is proposed. In order to provide close-to-100% throughput for any admissible multicast traffic patterns, a three-stage implementation of feedback-based switch is also designed.&#13;\n&#13;\nIn designing load balancing schemes for data centers, we focus on the most popular fat-tree based data centers. Notably, packet-based load balancing is widely considered infeasible for data centers. This is because the associated packet out-of-order problem will cause unnecessary TCP fast retransmits, and as a result, severely undermine TCP performance. In this thesis, we show that if packet-based load balancing is performed properly, the packet out-of-order problem can be easily addressed by slightly increasing the number of duplicate ACKs required for triggering fast retransmit. Admittedly, in case of a real packet loss, the loss recovery time will be increased. But our simulation results show that such an increase is far less than the reduction in the network queueing delay (due to a better load-balanced network). As compared to a flow-based load balancing scheme, our packet-based scheme consistently provides significantly higher goodput and noticeably smaller delay.