The up-coming Gbps high-speed networks are expected to support a wide range of communication-intensive, real-time multimedia applications. The requirement for timely delivery of digitized audio-visual information raises new challenges for the next generation integrated-service broadband networks. One of the key issues is the Quality-of-Service (QoS) routing. It selects network routes with sufficient resources for the requested QoS parameters. The goal of routing solutions is two-fold: (1) satisfying the QoS requirements for every admitted connection and (2) achieving the global efficiency in resource utilization. Many unicast/multicast QoS routing algorithms were published recently, and they work with a variety of QoS requirements and resource constraints. Overall, they can be partitioned into three broad classes: (1) source routing, (2) distributed routing and (3) hierarchical routing algorithms. In this paper we give an overview of the QoS routing problem as well as the existing solutions. We present the strengths and the weaknesses of different routing strategies and outline the challenges. We also discuss the basic algorithms in each class, classify and compare them, and point out possible future directions in the QoS routing area.

We formulate the problem of multicast tree generation as one of computing a directed Steiner tree of minimal cost. In this context, we present a polynomial-time algorithm that provides for tradeoff selection, using a single parameter , between the tree-cost (Steiner cost) and the runtime efficiency. Further, the same algorithm may be used for delay optimization or tree-cost minimization simply by configuring the value of appropriately. We present theoretical and experimental analysis characterizing the problem and the performance of our algorithm. Theoretically, we (1) show that it is highly unlikely that there exists a polynomial-time algorithm with a performance guarantee of constant times optimum cost, (2) introduce metrics for measuring the asymmetry of graphs, and (3) show that the worst-case cost of the tree produced by our algorithm is at most twice the optimum cost times the asymmetry, for two of these asymmetry metrics. For graphs with bounded asymmetry, this gives constant ...

Multicast (MC) routing algorithms capable of satisfying the quality of service (QoS) requirements of real-time applications will be essential for future high-speed networks. We compare the performance of all of the important MC routing algorithms when applied to networks with asymmetric link loads. Each algorithm is judged based on the quality of the MC trees it generates and its efficiency in managing the network resources. Simulation results over random networks show that unconstrained algorithms are not capable of fulfilling the QoS requirements of real-time applications in wide-area networks. Simulations also reveal that one of the unconstrained algorithms, reverse path multicasting (RPM), is quite inefficient when applied to asymmetric networks. We study how combining routing with resource reservation and admission control improves RPM’s efficiency in managing the network resources. The performance of one semiconstrained heuristic, MSC, three constrained Steiner tree (CST) heuristics, KPP, CAO, and BSMA, and one constrained shortest path tree (CSPT) heuristic, CDKS are also studied. Simulations show that the semiconstrained and constrained heuristics are capable of successfully constructing MC trees which satisfy the QoS requirements of real-time traffic. However, the cost performance of the heuristics varies. BSMA’s MC trees are lower in cost than all other constrained heuristics. Finally, we compare the execution times of all algorithms, unconstrained, semiconstrained, and constrained.

Multicast services have been increasingly used in large scale continuous media applications. The quality-of-service (QoS) requirements of these continuous media applications prompt the necessity for QoS-driven, constraint-based multicast routing. This article provides a comprehensive overview of existing multicast routing algorithms, protocols, and their QoS extension. In particular, we classify multicast routing problems according to their optimization functions and performance constraints, present basic routing algorithms in each problem class, and discuss their strengths and weakness. We also categorize existing multicast routing protocols, outline the issues and challenges in providing QoS in multicast routing, and point out possible future research directions.

The future Internet is expected to support multicast applications with quality of service (QoS) requirements. To facilitate this, QoS multicast routing protocols are pivotal in enabling new receivers to join a multicast group. However, current routing protocols are either too restrictive in their search for a feasible path between a new receiver and the multicast tree, or burden the network with excessive overhead. We propose QMRP, a new QoS-aware Multicast Routing Protocol. QMRP achieves scalability by significantly reducing the communication overhead of constructing a multicast tree, yet it retains a high chance of success. This is achieved by switching between single-path routing and multiple-path routing according to the current network conditions. The high level design of QMRP makes it operable on top of any unicast routing algorithm in both intra-domain and interdomain. Its responsiveness is improved by using a termination mechanism which detects the failure as well as the succes...

The increasing interest in distributed applications like multimedia and collaborative work calls for efficient means to support multicast communication. A fundamental issue in multicast communication is route selection, usually based on trees. We present a destinationdriven algorithm that optimizes for applications, such as group video- or tele-conferencing, that require multicast trees with low total cost. The destination-driven algorithm uses a greedy strategy based on shortest-path trees and minimal spanning trees but biases routes through destinations. The performance of the algorithm is analyzed through extensive simulation and compared with several Steiner tree heuristics and the popular shortest-path tree (SPT) method. The algorithm is found to produce trees with significantly lower overall cost than the SPT while maintaining reasonable per-destination performance. Its performance is also shown to compare well with other well-known Steiner heuristics. Moreover, the algorithm do...

Abstract—The delivery of quality video service often requires high bandwidth with low delay or cost in network transmission. Current routing protocols such as those used in the Internet are mainly based on the single-path approach (e.g., the shortest-path routing). This approach cannot meet the end-to-end bandwidth requirement when the video is streamed over bandwidth-limited networks. In order to overcome this limitation, we propose multipath routing, where the video takes multiple paths to reach its destination(s), thereby increasing the aggregate throughput. We consider both unicast (point-to-point) and multicast scenarios. For unicast, we present an efficient multipath heuristic (of complexity 3)), which achieves high bandwidth with low delay. Given a set of path lengths, we then present and prove a simple data scheduling algorithm as implemented at the server, which achieves the theoretical minimum end-to-end delay. For a network with unitcapacity links, the algorithm, when combined with disjoint-path routing, offers an exact and efficient solution to meet a bandwidth requirement with minimum delay. For multicast, we study the construction of multiple trees for layered video to satisfy the user bandwidth requirements. We propose two efficient heuristics on how such trees can be constructed so as to minimize the cost of their aggregation subject to a delay constraint. Index Terms—Bandwidth-delay constraints, multicast routing, multipath routing, quality-of-service (QoS) routing, video scheduling. I.

In multicasting routing, the main objective is to send data from one or more source to multiple destinations, while at the same time minimizing the usage of resources. Examples of resources which can be minimized include bandwidth, time and connection costs. In this paper we survey applications of combinatorial optimization to multicast routing. We discuss the most important problems considered in this area, as well as their models. Algorithms for each of the main problems are also presented.

In this report we present our work on a receiver-initiated approach called RIMQoS to support multicast with multiple QoS constraints and dynamic memberships. Assuming link-state information is available, a receiver computes a path to join the multicast tree rooted at the source. It then sends join request along the path to join the group. We first present the operation of our approach in an intra-domain setting with delay constraint. Then we introduce an algebraic formulation for multiple QoS constraints to show how to determine if QoS requirements for a new receiver can be satisfied at an intermediate node along the join path and how to adjust the tree without breaking QoS requirements for existing members if they are not. It attempts to minimize the cost of the tree by letting a node to join the tree via a low-cost path and may later switch to a higher-cost but more QoS stringent path when necessary. Our scheme builds multicast tree incrementally and thus supports fully dynamic memberships. It also supports of heterogeneous receivers seamlessly. Moreover, it can support any number of arbitrary QoS metrics without assuming any dependencies among them, if they satisfy some normal mathematical property. If implemented as a distributed routing protocol, our approach doesn't require any node to have explicit knowledge of the multicast tree topology, thus it scales well for multicast of large group. Simulation studies have been carried out to study its behavior and compare its performance with other schemes.

Many distributed real-time applications, such as audio- and video-conferencing and collaborative systems, require multicast support from the underlying network. Multicasting involves the delivery of messages over a tree rooted at the sender and whose paths lead to the various receivers. A major objective of the routing protocol is to build a tree with minimum cost. Finding such a tree is known to be computationally expensive, and many heuristics have been proposed to efficiently find near-optimal trees. Moreover, some heuristics exist to efficiently find multicast trees that are of low cost and satisfy Quality-of-Service (QoS) (e.g. delay) delivery constraints required by real-time applications. However, these heuristics are not fast enough for large-scale networks. In this paper, we present a fast algorithm, called QDMR, for generating delay-constrained low-cost multicast routing trees. A salient feature of QDMR is that it dynamically adjusts its low-cost tree construction policy base...