Showing papers on "Geographic routing published in 1987"

Deadlock-Free Message Routing in Multiprocessor Interconnection Networks

Abstract: A deadlock-free routing algorithm can be generated for arbitrary interconnection networks using the concept of virtual channels. A necessary and sufficient condition for deadlock-free routing is the absence of cycles in a channel dependency graph. Given an arbitrary network and a routing function, the cycles of the channel dependency graph can be removed by splitting physical channels into groups of virtual channels. This method is used to develop deadlock-free routing algorithms for k-ary n-cubes, for cube-connected cycles, and for shuffle-exchange networks.

Routing in the Manhattan Street Network

Abstract: The Manhattan Street Network is a regular, two-connected network, designed for packet communications in a local or metropolitan area. It operates as a slotted system, similar to conventional loop networks. Unlike loop networks, routing decisions must be made at every node in this network. In this paper, several distributed routing rules are investigated that take advantage of the regular structure of the network. In an operational network, irregularities occur in the structure because of the addressing mechanisms, adding single nodes, and failures. A fractional addressing scheme is described that makes it possible to add new rows or columns to the network without changing the addresses of existing nodes. A technique is described for adding one node at a time to the network, while changing only two existing links. Finally, two procedures are described that allow the network to adapt to node or link failures. The effect that irregularities have on routing mechanisms designed for a regular structure is investigated.

Method and apparatus for eliminating unsuccessful tries in a search tree

Abstract: A circuit switching system in an M-ary, n-cube connected network completes a best-first path from an originating node to a destination node by latching valid legs of the path as the path is being sought out. Each network node is provided with a routing hyperswitch sub-network, ("HSN") connected between that node and bidirectional high capacity communication channels of the n-cube network. The sub-networks are all controlled by routing algorithms which respond to message identification headings ("headers") on messages to be routed along one or more routing legs. The header includes information embedded therein which is interpreted by each sub-network to route and historically update the header. A logic circuit, available at every node, implements the algorithm and automatically forwards or back-tracks the header in the network legs of various paths until a completed path is latched.

Distributed routing unit for fully-automated flexible manufacturing system

Abstract: Segments-in-process (SIPs) of material are automatically routed through a material handling system by distributed routing units under the guidance of a host computer system. The material handling system comprises a network of intersecting material paths. A distributed routing unit is located at material path intersections. Information relating to the source, destination and identity of a SIP is provided to the host computer system by a client process. Typically the destination of the SIP is a process machine located on a material path. Upon receipt of the information from the client process, the host defines a sequence of distributed routing units through which the SIP will move from its source to its destination. Each distributed routing unit in the sequence is then provided with information which enables each unit to identify the SIP and to perform a task with respect thereto. The tasks are then sequentially performed such that the SIP is routed through the defined sequence to its destination. The SIP may be routed to its destination when the host computer system is off line.

A new look at fault-tolerant network routing

Abstract: We model a communication network as a graph in which a processor is a node and a communication link is an edge. A routing for such a network is a fixed path, or route, between each pair of nodes. Given a network with a predefined routing, we study the effects of faulty components on the routing. Of particular interest is the number of routes along which a message must travel between any two non-faulty nodes. This problem is analyzed for specific families of graphs and for classes of routings. We also give some bounds for general versions of the problem. Finally, we conclude with one of the most important contributions of this paper, a list of interesting and apparently difficult open problems.

Nonstationary models of learning automata routing in data communication networks

Abstract: In a data communication network the message traffic has peak and slack periods and the network topology may change. When the learning approach is applied to routing, a learning automation is situation at each node in the network. Each automation selects the routing choices at its node and modifies its strategy according to network conditions. A model of a nonstationary automaton environment, with response characteristics dynamically related to the probabilities of the actions performed on it, is proposed. The limiting behavior of the model is identical to that of the earlier models. Simulation studies of automata operating in simple queuing networks reinforce the analytical results and show that the parameters of the proposed model can be chosen to predict transient behavior.

Method and apparatus for routing message packets and recording the roofing sequence

Abstract: A message packet router is described that performs the functions of determining if a message packet is addressed to circuitry associated with the router, of routing message packets to their distination if possible and of storing message packets that cannot be routed on because of circuit conflicts. The router also provides additional functions of merging message packets addressed to the same destination, of saving the state of the router at each significant point in the message routing cycle, and of running the entire routing cycle backwards. This later feature makes it possible to broadcast message packets selectively to certain processors in the array.

Reduced distance routing in single-state shuffle-exchange interconnection networks

Abstract: In multiprocessor architectures, it is frequently necessary to provide parallel communication among a potentially large number of processors and memories. Among the many interconnection schemes that have been proposed and analyzed, shuffle-exchange networks have received much attention due to their ability to allow a message to pass from any node to any other node in a number of steps that grows only logarithmically with the number of interconnected nodes (in the absence of contention) while keeping the number of hardware connections per node independent of the number of nodes.Straight-forward use of shuffle-exchange networks to interconnect N nodes involves having every packet pass through log2N stages enroute to its destination. By exploiting common structure in the addresses of the source and destination nodes, however, more sophisticated routing can reduce the average number of steps per message below log2N. In this paper, we describe and evaluate three levels of improvements to basic single-stage shuffle-exchange routing. Each one yields successively more benefit at the cost of more complexity. Using simulation, we show that the use of routing schemes that reduce the average distance can substantially reduce average message delay times and increase interconnection network capacity. We quantify the performance gains only in the case where messages from one node are destined with uniform probability over all nodes. However, it is clear that the advantage of the new schemes we propose would be still greater if there is some “locality” of communication that can be exploited by having the most frequent communication occur between pairs of nodes with shorter distances separating them.

Packet routing algorithms for integrated switching networks

Abstract: Repeated studies have shown that a single switching technique, either circuit or packet switching, cannot optimally support a heterogeneous traffic mix composed of voice, video and data. Integrated networks support such heterogeneous traffic by combining circuit and packet switching in a single network. To manage the statistical variations of network traffic, we introduce a new, adaptive routing algorithm called hybrid, weighted routing. Simulations show that hybrid, weighted routing is preferable to other adaptive routing techniques for both packet switched networks and integrated networks.

Optimal Dynamic Routing in Multidestination Networks

Abstract: The dynamic routing problem for multiple destination networks is considered. The minimum time rather than total delay cost functional is employed. Each link capacity is optimally partitioned by examining the competition of bottlenecks associated with each destination. The multidestination problem is thus solved through an iterative link-by-link optimization.

A New Approach to Hierarchical Routing in Large Networks

Abstract: The overhead of an adaptive routing algorithm becomes prohibitive in a network with numerous nodes (in the order of hundreds or more) and a flat organization. In this paper, we present and analyze a new hierarchical routing algorithm for large networks. The algorithm is based on (1) the definition and maintenance of a hierarchical addressing scheme that is in turn based on the names of nodes that are well known in the network or within regions of the network, and (2) an extension of a new distributed routing algorithm first proposed by the author for flat networks.

An adaptive routing method for computer networks by electric‐circuit modeling

Abstract: The computer network and multiprocessor system have been developed and studied. They are based on a network composed of nodes containing processors, aiming at the improvement of performance by distributed processing as well as the improvement of reliability by resource distribution. To realize high system performance, adequate routing and flow controls are required in the communication of information among nodes. This paper proposes a new routing control scheme to be used in the packet communication in the computer network or multiprocessor system. The scheme is called potential routing, which models the computer network by an electric circuit, and the packet routing from the source node to the destination node is performed to the potential difference between the adjacent nodes. The node potential is determined first by Kirchhoff's law and is modified dynamically according to the traffic situation during the routing procedure, providing an adequate criterion for the routing. The proposed scheme has a feature in that ping-pong and loop phenomena, which cause traffic congestion, are not produced in principle. It was verified by simulation that the transmission delay is reduced when the traffic is high or unbalanced.

A New Hierarchical Scheme for Combined Routing and Flow Control in Data Networks by Application of Positive System Theory

Abstract: In this paper we shall present some new results obtained from an application of Positive System Theory [1] to the problem of designing combined routing and flow control strategies for data communication networks. This application permits treating the combined routing and flow control problem in the framework of system stabilization and results in a hierarchical control scheme. The overall control effort consists of a distributed computation of a set of routing parameters at the lower level of network nodes and a computation on a slower time-scale of a set of combined parameters by a Supervisor (Network Control Center) at a higher hierarchical level. Specific algorithms are presented for adaptive updating of these parameters in order to realize improved network performance taking into account multiple objectives of end-to-end delay, throughput and nodal buffer management. The combined routing and flow control problem is attaining a great deal of importance in the recent times. This is due to the fact that the routing schemes and the flow control schemes implemented in existing data networks are designed independent of each other, where-as it has recently been determined [2,3] that a high degree of interplay exists between the two forms of control which has to be taken into account for realizing improved network performance. It has also been determined that a hierarchical control structure provides a very useful mechanism for an integration of routing and flow control [4,5].