Showing papers on "Multipath routing published in 1995"

Probabilistic diversification and intensification in local search for vehicle routing

Abstract: This article presents a probabilistic technique to diversify, intensify, and parallelize a local search adapted for solving vehicle routing problems. This technique may be applied to a very wide variety of vehicle routing problems and local searches. It is shown that efficient first-level tabu searches for vehicle routing problems may be significantly improved with this technique. Moreover, the solutions produced by this technique may often be improved by a postoptimization technique presented in this article, too. The solutions of nearly forty problem instances of the literature have been improved.

A distributed routing algorithm for mobile wireless networks

Abstract: We present a loop-free, distributed routing protocol for mobile packet radio networks. The protocol is intended for use in networks where the rate of topological change is not so fast as to make “flooding” the only possible routing method, but not so slow as to make one of the existing protocols for a nearly-static topology applicable. The routing algorithm adapts asynchronously in a distributed fashion to arbitrary changes in topology in the absence of global topological knowledge. The protocol's uniqueness stems from its ability to maintain source-initiated, loop-free multipath routing only to desired destinations with minimal overhead in a randomly varying topology. The protocol's performance, measured in terms of end-to-end packet delay and throughput, is compared with that of pure flooding and an alternative algorithm which is well-suited to the high-rate topological change environment envisioned here. For each protocol, emphasis is placed on examining how these performance measures vary as a function of the rate of topological changes, network topology, and message traffic level. The results indicate the new protocol generally outperforms the alternative protocol at all rates of change for heavy traffic conditions, whereas the opposite is true for light traffic. Both protocols significantly outperform flooding for all rates of change except at ultra-high rates where all algorithms collapse. The network topology, whether dense or sparsely connected, is not seen to be a major factor in the relative performance of the algorithms.

A necessary and sufficient condition for deadlock-free adaptive routing in wormhole networks

Abstract: Deadlock avoidance is a key issue in wormhole networks. A first approach by W.J. Dally and C.L. Seitz (1987) consists of removing the cyclic dependencies between channels. Many deterministic and adaptive routing algorithms have been proposed based on that approach. Although the absence of cyclic dependencies is a necessary and sufficient condition for deadlock-free deterministic routing, it is only a sufficient condition for deadlock-free adaptive routing. A more powerful approach by J. Duato (1991) only requires the absence of cyclic dependencies on a connected channel subset. The remaining channels can be used in almost any way. In this paper, we show that the previously mentioned approach is also a sufficient condition. Moreover, we propose a necessary and sufficient condition for deadlock-free adaptive routing. This condition is the key for the design of fully adaptive routing algorithms with minimum restrictions, An example shows the application of the new theory. >

Fault-tolerant wormhole routing algorithms for mesh networks

Abstract: We present simple methods to enhance the current minimal wormhole routing algorithms developed for high radix, low dimensional mesh networks for fault tolerant routing. We consider arbitrarily located faulty blocks and assume only local knowledge of faults. Messages are routed minimally when not blocked by faults and this constraint is relaxed to route around faults. The key concept we use is a fault ring consisting of fault free nodes and links can be formed around each fault region. Our fault tolerant techniques use these fault rings to route messages around fault regions. We show that, using just one extra virtual channel per physical channel, the well known e cube algorithm can be used to provide deadlock free routing in networks with nonoverlapping fault rings; there is no restriction on the number of faults. For the more complex faults with overlapping fault rings, four virtual channels are used. We also prove that at most four additional virtual channels are sufficient to make fully adaptive algorithms tolerant to multiple faulty blocks in n dimensional meshes. All these algorithms are deadlock and livelock free. Further, we present simulation results for the e cube and a fully adaptive algorithm fortified with our fault tolerant routing techniques and show that good performance may be obtained with as many as 10% links faulty. >

A Location Based Heuristic for General Routing Problems

Abstract: We present a general framework for modeling routing problems based on formulating them as a traditional location problem called the capacitated concentrator location problem. We apply this framework to two classical routing problems: the capacitated vehicle routing problem and the inventory routing problem. In the former case, the heuristic is proven to be asymptotically optimal for any distribution of customer demands and locations. Computational experiments show that the heuristic performs well for both problems and, in most cases, outperforms all published heuristics on a set of standard test problems.

Routing subject to quality of service constraints in integrated communication networks

Abstract: With increasingly diverse QOS requirements, it is impractical to continue to rely on conventional routing paradigms that emphasize the search for an optimal path based on a predetermined metric, or a particular function of multiple metrics. Modern routing strategies must not only be adaptive to network changes but also offer considerable economy of scope. We consider the problem of routing in networks subject to QOS constraints. After providing an overview of prior routing work, we define various QOS constraints. We present a call architecture that may be used for QOS matching and a connection management mechanism for network resource allocation. We discuss fallback routing, and review some existing routing frameworks. We also present a new rule-based, call-by-call source routing strategy for integrated communication networks. >

Routing in Communications Networks

Abstract: I. CIRCUIT-SWITCHING NETWORKS. AT&Ts Dynamic Routing Network, G.R. Ash Dynamic Alternative Routing, R.J. Gibbens, F.P. Kelly, and P.B. Key II. PACKET-SWITCHING NETWORKS. Distance Vector Routing, G.S. Malkin and M.E. Steenstrup Inter-Domain Routing: EGP, BGP, and IDRP, Y. Rekhter Link State Routing, J. Moy AppleTalk Routing, A.B. Oppenheimer and F. Kuang SNA Routing, A. Garuge III. HIGH-SPEED NETWORKS. Routing in Optical Networks, J. Bannister, M. Gerla, and M. Kovacevic On Routing in ATM Networks, S. Gupta, K.W. Ross, and M. El Zarki Routing in the plaNET Network, I. Cidon and R. Guerin Deflection Routing, F. Borgonovo IV. MOBILE NETWORKS. Routing in Cellular Mobile Radio Communications Networks, J. Ketchum Packet Radio Routing, G.S. Lauder

Competitive routing of virtual circuits in ATM networks

Abstract: Classical routing and admission control strategies achieve provably good performance by relying on an assumption that the virtual circuits arrival pattern can be described by some a priori known probabilistic model. A new on-line routing framework, based on the notion of competitive analysis, was proposed. This framework is geared toward design of strategies that have provably good performance even in the case where there are no statistical assumptions on the arrival pattern and parameters of the virtual circuits. The on-line strategies motivated by this framework are quite different from the min-hop and reservation-based strategies. This paper surveys the on-line routing framework, the proposed routing and admission control strategies, and discusses some of the implementation issues. >

A family of fault-tolerant routing protocols for direct multiprocessor networks

Abstract: Our goal is to reconcile the conflicting demands of performance and fault-tolerance in interprocessor communication. To this end, we propose a pipelined communication mechanism-pipelined circuit-switching (PCS)-which is a variant of the well known wormhole routing (WR) mechanism. PCS relaxes some of the routing constraints imposed by WR and as a result enables routing behavior that cannot otherwise be realized. This paper presents a new class of adaptive routing algorithms-misrouting backtracking with m misroutes (MB-m). This class of routing algorithms is made possible by PCS. We provide an analysis of the performance and static fault-tolerant properties of MB-m. The results of an experimental evaluation of PCS and MB-3 are also presented. This methodology provides performance approaching that of WR, while realizing a level of resilience to static faults that is difficult to achieve with WR. >

Bandwidth-delay based routing algorithms

Abstract: Multimedia applications often require guaranteed quality of service and resource reservation, which has raised a number of challenging technical issues for routing. We consider two new routing algorithms based on bandwidth and delay metrics. The implications of routing metrics on path computation are examined and the rationales behind the selection of bandwidth and delay metrics are discussed. Two new routing algorithms based on bandwidth and delay metrics are presented and some of their important properties are investigated.

ROMM routing on mesh and torus networks

Abstract: ROMM is a class of Randomized, Oblivious, Multi--phase, Minimal routing algorithms. ROMM routing offers a potential for improved performance compared to both fully randomized algorithms and deterministic oblivious algorithms, under both light and heavy loads. ROMM routing also offers close to best case performance for many common routing problems. In previous work, these claims were supported by extensive simulations on binary cube networks [30, 31]. Here we present analytical and empirical results for ROMM routing on wormhole routed mesh and torus networks. Our simulations show that ROMM algorithms can perform several representative routing tasks 1.5 to 3 times faster than fully randomized algorithms, for medium--sized networks. Furthermore, ROMM algorithms are always competitive with deterministic, oblivious routing, and in some cases, up to 2 times faster.

Improved bounds for all optical routing

Abstract: We consider the ploying all optica P roblem of routing in networks emrouting technology. In these networks, messages travel in optical form and switchin is f! erformed directly on the optical signal. By using %. iferent uravelengths, several messages may use the same edge concurrently, Howeve!, messages assigned the same wavelength must use disjoznt paths, or else be routed at separate rounds. No bufferin at, intermediate nodes is available. Thus, routing in ing wavelengths, paths, and time slots messages. that For arbitrary bounded degree networks, we show any permutation can be routed efficiently in one round using at most 0(log2n/P2) wavelengths, where p is the edge expansion of the network. This improves a quadratic factor on previous results, and almost matches the R(1/P2) existential lower bound. We consider two of the more popular architectures for parallel corn uters. K For bounded dimension arrays we give the rst per-instance approximation algorithm. Given a limited number of wavelengths and a set, of messages to be routed, the algorithm approximates to within polylogarithmlc factors the optimal number of rounds necessary to route all messages. Previous results for arrays give on1 we show that on t K worst-case performance. Finally, e hypercube an be routed using only a constant num i: permutation can er of wavelengths. The previous known bound was O(log n).

Core selection methods for multicast routing

Abstract: Multicast routing is an important topic of both theoretical and practical interest. Several proposed multicast routing algorithms involve the designation of one or more network nodes as the "center" of the routing tree for each multicast group. The choice of this designated router (which we refer to as the "core") influences the shape of the multicast routing tree, and thus influences the performance of the routing scheme. We investigate the relationship between the choice of core and three performance measures. Specifically, we compare various methods of selecting a core with respect to their effect on the bandwidth, delay, and traffic concentration. We conclude that simple methods are adequate for widely distributed groups, but that the addition of group information can be leveraged to improve performance especially when the group is small or exhibits a high degree of locality. We also conclude that core choice can be used to control traffic concentration, in fact traffic concentration effects can be ameliorated by appropriate core choice policies.

Distributed, scalable routing based on vectors of link states

Abstract: We have present a new method for distributed routing in computer networks and internets using link-state information. Link vector algorithms (LVA) are introduced for the distributed maintenance of routing information in large networks and internets.

The message flow model for routing in wormhole-routed networks

Abstract: In this paper, we introduce a new approach to deadlock-free routing in wormhole-routed networks called the message flow model. This method may be used to develop deterministic, partially-adaptive, and fully-adaptive routing algorithms for wormhole-routed networks with arbitrary topologies. We first establish the necessary and sufficient condition for deadlock free routing, based on the analysis of the message flow on each channel. We then use the model to develop new adaptive routing algorithms for 2D meshes. >

Method and apparatus for deadlock-free routing around an unusable routing component in an N-dimensional network

Abstract: A method and apparatus for deadlock-free routing around an unusable routing component in a network reroutes paths between source and destination nodes by initially identifying an unusable routing component. A shadow direction within the network is then determined, the shadow direction being from the unusable routing component to an edge of the network. The paths between nodes are then rerouted so that the paths bypass the unusable routing component and limit the use of any routing components in the network between the unusable routing component and the edge in the shadow direction.

Communication in Multicomputers with Nonconvex Faults

Abstract: A technique to enhance multicomputer routers for fault-tolerant routing with modest increase in routing complexity and resource requirements is described. This method handles solid faults in meshes, which includes all convex faults and many practical nonconvex faults, for example, faults in the shape of L or T. As examples of the proposed method, adaptive and nonadaptive fault-tolerant routing algorithms using four virtual channels per physical channel are described.

Fault-tolerant adaptive routing for two-dimensional meshes

Abstract: Many massively parallel computers in use today utilize simple deterministic XY wormhole routing to transmit messages between nodes. Because XY routing does not provide any routing adaptability, it lacks the ability to avoid congested links, as well as faults. Therefore, the focus of this paper will be two-fold: improving the performance of wormhole routing and providing fault tolerance for up to N-1 faults in an N/spl times/N two-dimensional mesh. A simulation model based on the Intel Paragon is presented that compares several known routing strategies with the proposed strategy to illustrate how local state information can be used to provide a potential network throughput improvement of up to 20%, while achieving fault tolerance. >

Hierarchical distance-vector multicast routing for the MBone

Abstract: The exponential growth of the Multicast Back-bone (MBone) has resulted in increased routing overhead and processing costs. In this paper we propose a two-level hierarchical routing model as a solution to this problem. This approach involves partitioning the MBone into non-overlapping regions using DVMRP as the inter-region routing protocol; intra-region routing may be accomplished by any of a number of existing multicast protocols. Our design is flexible enough to accommodate additional levels of hierarchy, and protocols other than DVMRP at the higher levels. The unique feature of this approach is the independence of the higher level routing protocol from the subnet addresses, which allows for easy incremental deployment with small changes to existing intra-region protocols.

Vehicle Routing Problem with Fuzzy Due-Time Using Genetic Algorithms

Abstract: 1050 preference very well. Even though customers are asked to provide a fixed time window for service, they really hope to be served at a desired time if possible, We call such a desired time the due-time, In such case, the preference information of customers can be naturally represented as a convex fuzzy number with respect to the satisfaction for service time, In the paper, we suggest to use the concept of fuzzy due-time to replace the concept of time window because it can describe customers preference better than fixed time-window. Thus we can use the mathematics of fuzzy calculus to handle these imprecise descriptions of cus-

Method for automatically routing circuits of very large scale integration (VLSI)

Abstract: An automated routing tool for routing interconnections between circuit elements, standard cells and/or cell blocks of cell-based designs which incorporates the best features of both currently known gate array routing techniques with currently known cell-based routing techniques. The invention eliminates the disadvantages of permitting the detailed router to adjust the relative positions of the circuit elements, standard cells and/or cell blocks during the detailed routing process. The method employs a topology manager which iteratively compacts the circuit topology while at the same time optimizing the routing of the interconnections among the circuit elements, standard cells and/or cell blocks of the circuit design. The method employs bin-based global routing, which identifies expandable boundaries and which provides input to a compaction routine which expands or contracts the expandable areas in accordance with the result of the global routing process. The detailed routing step is not performed until after the relative positions of the circuit elements, cells and/or cell blocks have been already fixed.

Minimum-cost bounded-skew clock routing

Abstract: In this paper, we present a new clock routing algorithm which minimizes total wirelength under any given path-length skew bound. The algorithm constructs a bounded-skew tree (BST) in two steps: (i) a bottom-up phase to construct a binary tree of shortest-distance feasible regions which represent the loci of possible placements of clock entry points, and (ii) a top-down phase to determine the exact locations of clock entry points. Experimental results show that our clock routing algorithm, named BST/DME, can produce a set of routing solutions with skew and wirelength trade-off.

Link-state routing

Abstract: ƒ Same assumptions/goals, but different idea than DV: ƒ Tell all routers the topology and have each compute best paths ƒ Two phases: 1. Topology dissemination (flooding)-New News travels fast.-Old News should eventually be forgotten 2. Shortest-path calculation (Dijkstra's algorithm)-nlogn

A theory of deadlock-free adaptive multicast routing in wormhole networks

Abstract: A theory for the design of deadlock-free adaptive routing algorithms for wormhole networks, proposed by the author (1991, 1993), supplies sufficient conditions for an adaptive routing algorithm to be deadlock-free, even when there are cyclic dependencies between channels. Also, two design methodologies were proposed. Multicast communication refers to the delivery of the same message from one source node to an arbitrary number of destination nodes. A tree-like routing scheme is not suitable for hardware-supported multicast in wormhole networks because it produces many headers for each message, drastically increasing the probability of a message being blocked. A path-based multicast routing model was proposed by Lin and Ni (1991) for multicomputers with 2D-mesh and hypercube topologies. In this model, messages are not replicated at intermediate nodes. This paper develops the theoretical background for the design of deadlock-free adaptive multicast routing algorithms. This theory is valid for wormhole networks using the path-based routing model. It is also valid when messages with a single destination and multiple destinations are mixed together. The new channel dependencies produced by messages with several destinations are studied. Also, two theorems are proposed, developing conditions to verify that an adaptive multicast routing algorithm is deadlock-free, even when there are cyclic dependencies between channels. As an example, the multicast routing algorithms of Lin and Ni are extended, so that they can take advantage of the alternative paths offered by the network. >

Memory requirement for universal routing schemes

Abstract: Laboratoire de l'Informatique du Paral141isme-CNRS Ecole Normale Sup6rieure de Lyon 69364 Lyon cedex 07 France Abstract In this paper, we deal with the compact routing problem , that is implementing routing schemes that use a minimum memory size on each router. In [20], Peleg and Upfal showed that there is no hope to do that with less than a total f2(nl+llt2S+4)) memory bits for any stretch factor s z 1. We improve this bound for stretch factors s < 2 by proving that any near-shortest path routing scheme uses a total of Q(n2) memory bits. 1 Introduction The general routing problem in a network (as opposed to the permutation routing problem [18] or the broadcasting problem [6]) consists of fiding a routing protocol or routing function such that, for any source-destination pair, any message from the source can be routed to the destination. XY-routing [2] or e-cube routing [3] are such protocols. The efficiency of a protocol is measured in terms of latency (related to the length of the paths) and/or throughput (related to link or node congestion). Finding shortest paths in a network is easy [14], ~d finding paths minimizing congestion can be done easily for a large class of networks (namely Cayley graphs) [16]. However, the routings protocols that are obtained may be of no use from a VLSI point of view. Indeed, the implementation of these protocols may require such a large amount of hardware that they cannot be used in practice. For instance, implementing XY or e-cube routing is simple because routing is locally performed by respectively comparison and XOR-ing of the local address with the destination address. However, net works do not necessarily have the simde structure of meshes or hv-. percubes. For instance routing in pancake networks requires to decompose any given permutation in a product of particular ones, and this is definitely not easy (see Problem 39 in [9]). Also, networks may even have no Permission to make digital/hard copies of all or part of this material for personal or cIassroom use is granted without fee provided that the copies are not made or distributed for profit or commercial advantage, the copyright notice, the title of the publication and its date appear, and notice is given that copyright is by permission of the ACM, Inc. To copy otherwise, to republish, to post on servers or to redistribute to lists, requires speeitic permission and/or …

Method of on-line permanent virtual circuit routing

Abstract: A method of on-line routing of permanent virtual circuits is disclosed. The method uses an exponential cost function based on the network state and virtual circuit parameters to determine paths for the virtual circuits without scaling. The method may also advantageously use information available when multiple virtual circuits are requested to determine paths for the virtual circuits. Additionally, the method allows the routing selection to be refined so that the total cost of routing all the virtual circuits is reduced.

Call processing to provide number portability

Abstract: A method of routing a call including a called number in a communications network such as a Public Switched Telephone Network (PSTN), the method including determining if the called number is a network routing number indicating a specific switching node and line associated therewith in the communications network and routing the call within the communications network based on the called number when the called number is a network routing number. Additionally, the method includes identifying a network routing number based on the called number when the called number is not equal to the network routing number and routing the call within the communications network based on the identified network routing number.