Showing papers on "Static routing published in 1995"

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. >

A routing protocol for packet radio networks

Abstract: : The authors present a new distance-vector routing protocol for a packet radio network. The new distributed routing protocol, Wireless Routing Protocol (WRP), works on the notion of second-to-last hop node to a destination. WRP reduces the number of cases in which a temporary routing loop can occur and also provides a mechanism for the reliable transmission of update messages. The performance of WRP has been compared quantitatively by simulations with that of distributed Bellman-Ford (DBF), DUAL (a loop-free, distance-vector algorithm), and an ideal link-state algorithm (ILS) that represents the state of the art of Internet routing in a highly dynamic environment. The simulation results indicate that WRP is the most efficient of the algorithms simulated in a wireless environment.

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. >

Collective communication in wormhole-routed massively parallel computers

Abstract: Most MPC networks use wormhole routing to reduce the effect of path length on communication time. Researchers have exploited this by designing ingenious algorithms to speed collective communication. Many projects have addressed the design of efficient collective communication algorithms for wormhole-routed systems. By exploiting the relative distance-insensitivity of wormhole routing, these new algorithms often differ fundamentally from their store-and-forward counterparts. We examine software and hardware approaches to implementing collective communication operations. Although we emphasize methods in which the underlying architecture is a direct network, such as a hypercube or mesh, as opposed to an indirect switch-based network, several approaches apply to systems of either type. We illustrate several issues arising in this research area and describe the major classes of algorithms proposed to solve these problems.

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. >

Method and system for routing packets in a packet communication network using locally constructed routine tables

Abstract: In a packet communication system, wherein nodes are assigned an absolute coordinate-based address and routing decisions are made at each node (S2, S7) without the use of directory-based routing, routing decisions made for a particular packet with an ultimate destination are stored at each node so that the next packet sent by that node to that same ultimate destination can be forwarded in accordance with the previous routing decision made for that destination. Routing decisions are stored locally at each node in a routing table (S6, S12). In one embodiment, nodes also store routing information about the source node for a packet so that when a return packet is received for the original source, the relay node will not have to make a routing decision.

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. >

Method and apparatus for routing for virtual networks

Abstract: An internetwork routing protocol which supports virtual networks Routing tables are maintained in routers or gateways which identify whether or not a destination is directly reachable by the router listed in the routing information entry, or whether it is merely part of a virtual network served by the listed destination routers For directly reachable connections, datagrams may be directly delivered to any router claiming such status with respect to the network with assurance of likely delivery to the destination Routers in communication with a virtual network must first be queried for the identity of a particular destination router address before packets are delivered to eliminate the need of packet forwarding

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.

Planar-adaptive routing: low-cost adaptive networks for multiprocessors

Abstract: Network throughput can be increased by allowing multipath, adaptive routing. Adaptive routing allows more freedom in the paths taken by messages, spreading load over physical channels more evenly. The flexibility of adaptive routing introduces new possibilities of deadlock. Previous deadlock avoidance schemes in k-ary n-cubes require an exponential number of virtual channels. We describe a family of deadlock-free routing algorithms, called planar-adaptive routing algorithms, that require only a constant number of virtual channels, independent of networks size and dimension. Planar-adaptive routing algorithms reduce the complexity of deadlock prevention by reducing the number of choices at each routing step. In the fault-free case, planar-adaptive networks are guaranteed to be deadlock-free. In the presence of network faults, the planar-adaptive router can be extended with misrouting to produce a working network which remains provably deadlock free and is provably livelock free. In addition, planar-adaptive networks can simultaneously support both in-order and adaptive, out-of-order packet delivery.Planar-adaptive routing is of practical significance. It provides the simplest known support for deadlock-free adaptive routing in k-ary n-cubes of more than two dimensions (with k>2). Restricting adaptivity reduces the hardware complexity, improving router speed or allowing additional performance-enhancing network features. The structure of planar-adaptive routers is amenable to efficient implementation.Simulation studies show that planar-adaptive routers can increase the robustness of network throughput for nonuniform communication patterns. Planar-adaptive routers outperform deterministic routers with equal hardware resources. Further, adding virtual lanes to planar-adaptive routers increases this advantage. Comparisons with fully adaptive routers show that planar-adaptive routers, limited adaptive routers, can give superior performance. These results indicate the best way to allocate router resources to combine adaptivity and virtual lanes.Planar-adaptive routers are a special case of limited adaptivity routers. We define a class of adaptive routers with f degrees of routing freedom. This class, termed f-flat adaptive routers, allows a direct cost-performance tradeoff between implementation cost (speed and silicon area) and routing freedom (channel utilization). For a network of a particular dimension, the cost of adaptivity grows linearly with the routing freedom. However, the rate of growth is a much larger constant for high-dimensional networks. All of the properties proven for planar-adaptive routers, such as deadlock and livelock freedom, also apply to f-flat adaptive routers.

Evaluation of multicast routing algorithms for real-time communication on high-speed networks

Abstract: Multicast (MC) routing algorithms capable of satisfying the 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 tree 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. One algorithm, reverse path multicasting, is not suitable for asymmetric networks irrespective of the requirements of the application. The three constrained Steiner tree (CST) heuristics reported to date are also studied. Simulations show that all three heuristics behave similarly and that they can manage the network efficiently and construct low cost MC trees that satisfy the QoS requirements of real-time traffic. The execution times of the CST heuristics depend on the MC group size, but they are always larger than those of the unconstrained algorithms.

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.

Transaction message routing in digital communications networks

Abstract: Packet messages transmitted on a packet communications network include origin and destination addresses in the form of stacked address elements which can be pushed or popped off of the stack. A plurality of interconnected packet communications network include routing nodes which utilize the top address element on the destination stack to route the message. Such routing nodes also include stack element editing facilities for popping elements from the stacks, constructing new elements to be pushed onto the stacks, and amending the contents of elements on the stack. This arrangement allows messages to be launched on the networks where the originating station does not have full knowledge of the destination station, and the routing nodes add the necessary destination information as it becomes necessary for routing.

Method and apparatus for routing and link metric assignment in shortest path networks

Abstract: The invention discloses a method and apparatus for assigning link "distance" metrics that result in near optimal routing for a network formed of nodes (routers) and links, where each link has a capacity associated with it, and where source-destination flows are given. The routing optimality is measured with respect to some objective function (e.g., average network delay).

Chapter 1 Vehicle routing

Abstract: Publisher Summary This chapter presents the most important algorithms that have been developed for model of the vehicle routing problem. However, before plunging into the mathematical development, it will be helpful to consider some examples of vehicle routing problems and various practical issues that arise in the use of vehicle routing models. Vehicle routing problems are all around us in the sense that many consumer products such as soft drinks, beer, bread, snack foods, gasoline and pharmaceuticals are delivered to retail outlets by fleets of trucks whose operation fits the vehicle routing model. Other examples of vehicle routing problems include the delivery of liquefied industrial gases and the collection of milk from farms for transportation to a processing center. Many companies have reported successful implementation of mathematical algorithms to optimize trucking operations including Air Products and Chemicals, Chevron, DuPont, Edward Don and Company etc. Two approaches have been taken to providing geographic information. The first approach is easy to implement and thus preferred if it is accurate enough. It consists of assigning coordinates to each customer and assuming that the travel distance between customers is the Euclidean distance between their coordinate pairs. Cost is taken to be proportional to distance. The distance is often scaled up by a factor to compensate for roads that deviate from a straight-line path between customers. The second approach obtains travel distances by applying a shortest route algorithm to a computerized network model of the road system.

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.

A new exact algorithm for the vehicle routing problem based on q -paths and k -shortest paths relaxations

Abstract: We consider the basic Vehicle Routing Problem (VRP) in which a fleet ofM identical vehicles stationed at a central depot is to be optimally routed to supply customers with known demands subject only to vehicle capacity constraints. In this paper, we present an exact algorithm for solving the VRP that uses lower bounds obtained from a combination of two relaxations of the original problem which are based on the computation ofq-paths andk-shortest paths. A set of reduction tests derived from the computation of these bounds is applied to reduce the size of the problem and to improve the quality of the bounds. The resulting lower bounds are then embedded into a tree-search procedure to solve the problem optimally. Computational results are presented for a number of problems taken from the literature. The results demonstrate the effectiveness of the proposed method in solving problems involving up to about 50 customers and in providing tight lower bounds for problems up to about 150 customers.

Packet routing system and method for achieving uniform link usage and minimizing link load

Abstract: Data packets are routed among nodes of a communication system in a uniform fashion. Substantial uniform link usage is achieved within allowed routes determined by end to end transport delay criteria. Initial routes are selected for each source--destination pair from alternative minimal hop routes. Link usage probabilities are calculated for the links involved in each route and system network routing entropy is calculated from the link usage probabilities. Final routes are chosen to maximize the network routing entropy resulting in uniform usage of the system's communication links in proportion to link capacity. The aggregate link load is also minimized. Individual routing tables are generated for each communication node based on the selected routes. The routing tables reflect changes in the traffic demand, changes in link capacity and changes in node connectivity within the constellation which occur as a result of satellite motion.

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.

Chapter 5 Arc routing methods and applications

Abstract: Publisher Summary The term "arc routing" refers to routing problems where the key service activity is to cover arcs of a transportation network. In contrast to node routing, where the key service activity occurs at the nodes (customer sites) and arcs are of interest only as elements of paths that connect the nodes, arc routing focuses on the traversal of edges. Practical examples include the routing of street sweepers, snow-plowing, salt gritting (covering streets with salt grit), and inspection of streets for maintenance, postal delivery, and meter reading. In all examples, each street segment must be covered in its entirety. In meter reading, postal delivery, and the delivery of telephone books, the density of the customer locations along a street segment is sufficiently high to consider the street segment as a whole as the service entity. The basic methodology of arc routing by discussing generic arc routing models and their solution techniques is discussed. The chapter covers well-known postman problems that can be regarded as the classical problems of arc routing. The basic objective of these problems is to cover all arcs of a given network with an Euler cycle of minimum cost. The chapter considers the capacitated arc routing problem, where each vehicle tour (cycle) must observe an explicit capacity constraint. Two manufacturing problems that can be modeled as rural postman problems and also mentions other routing applications are discussed in the chapter.

A preservation-based multicast (RBM) routing protocol for mobile networks: initial route construction phase

Abstract: We propose a combined multicast routing, resource reservation and admission control protocol, termed Reservation-Based Multicast (RBM), that borrows the “Rendez-vous Point” or “Core” concept from multicast routing algorithms proposed for the Internet, but which is intended for operation in mobile networks and routes hierarchically-encoded data streams based on user-specified fidelity requirements, real-time delivery thresholds and prevailing network bandwidth constraints. The protocol exhibits the fully distributed operation and receiver-initiated orientation of these proposed algorithms; but, unlike them, the protocol is tightly coupled to a class of underlying, distributed, unicast routing protocols thereby facilitating operation in a dynamic topology. This paper focuses on the initial route construction phase, assumed to occur during a static “snapshot” of the dynamic topology, and is therefore applicable to fixed networks as well, e.g. the Internet.

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. >

Topological design and routing for low-Earth orbit satellite networks

Abstract: We investigate a topological design and routing problem for low Earth orbit (LEO) satellite communication networks where each satellite can have a limited number of direct inter-satellite links (ISLs) to a subset of satellites within its line-of-sight. First, we model LEO satellite network as a FSA (finite state automaton) using satellite constellation information. Second, we solve a combined topological design and routing problem for each configuration corresponding to a state in the FSA. The topological design (or link assignment) problem deals with the selection of ISLs, and the routing problem handles the traffic distribution over the selected links to maximize the number of carried calls. This NP-complete mixed integer optimization problem is solved by a two-step heuristic algorithm that first solves the topological design problem, and then finds the optimal routing. The algorithm is iterated using the simulated annealing technique until the near-optimal solution is found. The link assignment table and the routing table that are pre-calculated off-line for each state are loaded into the satellites and a new set of these tables are retrieved at each state transition. The simulation result shows that the proposed method is applicable to practical LEO satellite networks.

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.

On wavelength translation in all-optical networks

Abstract: In this paper we study the benefits of wavelength translation in all-optical networks providing clear channel circuit-switching among users. We first establish approximate analytical models for a static-routing circuit-switched network with an arbitrary topology, both with and without wavelength translation. We then study performance of the non-blocking centralized switch, the mesh-torus network and the ring network, using the analytical models and simulation results. It is shown that the analytical models match the simulation results very well in the case of the centralized switch and the mesh network. The results of our study also show that the benefits of wavelength translation are marginal for the centralized switch and the ring network. On the other hand, the results show that wavelength translation can significantly improve performance of a large mesh network.

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. >