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92
Approximation Algorithms for Directed Steiner Problems
 Journal of Algorithms
, 1998
"... We give the first nontrivial approximation algorithms for the Steiner tree problem and the generalized Steiner network problem on general directed graphs. These problems have several applications in network design and multicast routing. For both problems, the best ratios known before our work we ..."
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Cited by 177 (8 self)
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We give the first nontrivial approximation algorithms for the Steiner tree problem and the generalized Steiner network problem on general directed graphs. These problems have several applications in network design and multicast routing. For both problems, the best ratios known before our work were the trivial O(k)approximations. For the directed Steiner tree problem, we design a family of algorithms that achieves an approximation ratio of i(i \Gamma 1)k 1=i in time O(n i k 2i ) for any fixed i ? 1, where k is the number of terminals. Thus, an O(k ffl ) approximation ratio can be achieved in polynomial time for any fixed ffl ? 0. Setting i = log k, we obtain an O(log 2 k) approximation ratio in quasipolynomial time. For the directed generalized Steiner network problem, we give an algorithm that achieves an approximation ratio of O(k 2=3 log 1=3 k), where k is the number of pairs of vertices that are to be connected. Related problems including the group Steiner...
A Distributed Algorithm for DelayConstrained Unicast Routing
 IEEE INFOCOM'97
, 1997
"... In this paper, we study the NPhard delayconstrained leastcost path problem, and propose a simple, distributed heuristic solution: the delayconstrained unicast routing (DCUR) algorithm. DCUR requires limited network state information to be kept at each node: a cost vector and a delay vector. We p ..."
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Cited by 97 (1 self)
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In this paper, we study the NPhard delayconstrained leastcost path problem, and propose a simple, distributed heuristic solution: the delayconstrained unicast routing (DCUR) algorithm. DCUR requires limited network state information to be kept at each node: a cost vector and a delay vector. We prove DCUR's correctness by showing that it is always capable of constructing a loopfree delayconstrained path within finite time, if such a path exists. The worst case message complexity of DCUR is O(V&sup3;) messages, where V is the number of nodes. However, simulation results show that,on the average, DCUR requires much fewer messages. Therefore, DCUR scales well to large networks. We also use simulation to compare DCUR to the optimal algorithm, and to the leastdelay path algorithm. Our results show that DCUR's path costs are within 10% from those of the optimal solution.
Pricing Multicast Communication: A CostBased Approach
 Telecommunication Systems
, 2001
"... Multicast and unicast traffic share and compete for network resources. A costbased approach to multicast pricing, based on accurate characterization of multicast scalability, will facilitate the efficient and equitable resource allocation between traffic types. Through the quantification of link us ..."
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Cited by 77 (0 self)
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Multicast and unicast traffic share and compete for network resources. A costbased approach to multicast pricing, based on accurate characterization of multicast scalability, will facilitate the efficient and equitable resource allocation between traffic types. Through the quantification of link usage, this paper establishes a multicast scaling relationship: the cost of a multicast distribution tree varies at the 0.8 power of the multicast group size. This result is validated with both real and generated networks, and is robust across topological styles and network sizes. Since multicast cost can be accurately predicted given the membership size, there is strong motivation to price multicast according to membership size. Furthermore, a price ceiling should be set to account for the effect of tree saturation. This tariff structure is superior to either a purely membershipbased or a flatrate pricing scheme, since it reflects the actual tree cost at all group membership levels. Keywords: multicast pricing, multicast scaling 1.
An Iterative Algorithm for DelayConstrained MinimumCost Multicasting
 IEEE/ACM Transactions on Networking
, 1998
"... The bounded shortest multicast algorithm (BSMA) is presented for constructing minimumcost multicast trees with delay constraints. BSMA can handle asymmetric link characteristics and variable delay bounds on destinations, specified as real values, and minimizes the total cost of a multicast routing ..."
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Cited by 57 (1 self)
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The bounded shortest multicast algorithm (BSMA) is presented for constructing minimumcost multicast trees with delay constraints. BSMA can handle asymmetric link characteristics and variable delay bounds on destinations, specified as real values, and minimizes the total cost of a multicast routing tree. Instead of the singlepass tree construction approach used in most previous heuristics, the new algorithm is based on a feasiblesearch optimization strategy that starts with the minimumdelay multicast tree and monotonically decreases the cost by iterative improvement of the delaybounded multicast tree. BSMA's expected time complexity is analyzed, and simulation results are provided showing that BSMA can achieve nearoptimal cost reduction with fast execution.
A Survey of Combinatorial Optimization Problems in Multicast Routing
, 2003
"... 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 c ..."
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Cited by 40 (1 self)
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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.
Search Space Reduction in QoS Routing
 In Proceedings of the 19th International Conference on Distributed Computing Systems
, 2001
"... To provide realtime service or engineer constrainedbased paths, networks require the underlying routing algorithm to be able to find lowcost paths that satisfy given QualityofService (QoS) constraints. However, the problem of constrained... ..."
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Cited by 38 (3 self)
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To provide realtime service or engineer constrainedbased paths, networks require the underlying routing algorithm to be able to find lowcost paths that satisfy given QualityofService (QoS) constraints. However, the problem of constrained...
A distributed algorithm of delaybounded multicast routing for multimedia applications in wide area networks
 IEEE/ACM Transactions on Networking Vol.6 No.6
, 1998
"... Abstract—Multicast routing is to find a tree which is rooted from a source node and contains all multicast destinations. There are two requirements of multicast routing in many multimedia applications: optimal network cost and bounded delay. The network cost of a tree is defined as the sum of the c ..."
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Cited by 37 (1 self)
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Abstract—Multicast routing is to find a tree which is rooted from a source node and contains all multicast destinations. There are two requirements of multicast routing in many multimedia applications: optimal network cost and bounded delay. The network cost of a tree is defined as the sum of the cost of all links in the tree. The bounded delay of a routing tree refers to the feature that the accumulated delay from the source to any destination along the tree shall not exceed a prespecified bound. This paper presents a distributed heuristic algorithm which generates routing trees having a suboptimal network cost under the delay bound constraint. The proposed algorithm is fully distributed, efficient in terms of the number of messages and convergence time, and flexible in dynamic membership changes. A large amount of simulations have been done to show the network cost of the routing trees generated by our algorithm is similar to, or even better than, other existing algorithms. Index Terms — Delaybounded multicast, distributed routing algorithm, multicast routing, multimedia systems, realtime communications. I.
Alternate Path Routing for Multicast
, 2000
"... Alternate path routing has been wellexplored in telecommunication networks as a means of decreasing the call blocking rate and increasing network utility. However, aside from some work applying these concepts to unicast flows, alternate path routing has received little attention in the Internet com ..."
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Cited by 31 (0 self)
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Alternate path routing has been wellexplored in telecommunication networks as a means of decreasing the call blocking rate and increasing network utility. However, aside from some work applying these concepts to unicast flows, alternate path routing has received little attention in the Internet community. We describe and evaluate an architecture for alternate path routing for multicast flows. For path installation, we design a receiveroriented alternate path protocol and prove that it reconfigures multicast trees without introducing loops. For path computation, we propose a scalable local search heuristic that allows receivers to find alternate paths using only partial network information. We use a simulation study to demonstrate the ability of local search to find alternate paths approximately as well as a linkstate protocol, with much lower overhead. I.
QDMR: An Efficient QoS Dependent Multicast Routing Algorithm
 Proceeding of 5 th IEEE realtime technology and application symposium (RTAS ’99
, 1998
"... Many distributed realtime applications, such as audio and videoconferencing 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 obje ..."
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Cited by 29 (0 self)
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Many distributed realtime applications, such as audio and videoconferencing 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 nearoptimal trees. Moreover, some heuristics exist to efficiently find multicast trees that are of low cost and satisfy QualityofService (QoS) (e.g. delay) delivery constraints required by realtime applications. However, these heuristics are not fast enough for largescale networks. In this paper, we present a fast algorithm, called QDMR, for generating delayconstrained lowcost multicast routing trees. A salient feature of QDMR is that it dynamically adjusts its lowcost tree construction policy base...
Practical limits on achievable energy improvements and useable delay tolerance in correlation aware data gathering in wireless sensor networks
 in Proc. IEEE Communications Society Conference on Sensor, Mesh and Ad Hoc Communications and Networks (SECON), 2005
"... Abstract — Correlation of data sent by different sensors in a wireless sensor network can be exploited during the data gathering process to improve energy efficiency. In this paper, we study the energy efficiency of correlation aware data aggregation trees under various sensor network conditions and ..."
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Cited by 22 (0 self)
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Abstract — Correlation of data sent by different sensors in a wireless sensor network can be exploited during the data gathering process to improve energy efficiency. In this paper, we study the energy efficiency of correlation aware data aggregation trees under various sensor network conditions and the tradeoffs involved in using them. The following two related questions are specifically investigated in the study: (i) Is there any practical limit on the achievable improvement in energy efficiency in adopting a correlation aware aggregation structure as opposed to a correlation unaware structure? (ii) Is there a practical maximum useable delay bound that can deliver the maximum achievable improvement? In answering the above questions, we present comprehensive simulation results and draw inferences based on the results. We also conclude two rather surprising results that the energy improvement in using correlation aware aggregation is not significant under many network scenarios, and the maximum useable delay bound is not large compared with the delay along the maximum length shortestpath in the default shortest path tree. I.