Showing papers on "Destination-Sequenced Distance Vector routing published in 1988"

Multicast routing in internetworks and extended LANs

Abstract: Multicasting is used within local-area networks to make distributed applications more robust and more efficient. The growing need to distribute applications across multiple, interconnected networks, and the increasing availability of high-performance, high-capacity switching nodes and networks, lead us to consider providing LAN-style multicasting across an internetwork. In this paper, we propose extensions to two common internetwork routing algorithms—distance-vector routing and link-state routing—to support low-delay datagram multicasting. We also suggest modifications to the single-spanning-tree routing algorithm, commonly used by link-layer bridges, to reduce the costs of multicasting in large extended LANs. Finally, we show how different link-layer and network-layer multicast routing algorithms can be combined hierarchically to support multicasting across large, heterogeneous internetworks.

Survey Paper—Time Window Constrained Routing and Scheduling Problems

Abstract: We have witnessed recently the development of a fast growing body of research focused on vehicle routing and scheduling problem structures with time window constraints. It is the aim of this paper to survey the significant advances made for the following classes of routing problems with time windows: the single and multiple traveling salesman problem, the shortest path problem, the minimum spanning tree problem, the generic vehicle routing problem, the pickup and delivery problem including the dial-a-ride problem, the multiperiod vehicle routing problem and the shoreline problem. Having surveyed the state-of-the-art in this area, we then offer some perspectives on future research.

A tradeoff between space and efficiency for routing tables

Abstract: Two conflicting goals play a crucial role in the design of routing schemes for communication networks. A routing scheme should use as short as possible paths for routing messages in the network, while keeping the routing information stored in the processors' local memory as succinct as possible. The efficiency of a routing scheme is measured in terms of its stretch factor - the maximum ratio between the length of a route computed by the scheme and that of a shortest path connecting the same pair of vertices.Most previous work has concentrated on finding good routing schemes (with a small fixed stretch factor) for special classes of network topologies. In this work we study the problem for general networks, and look at the entire range of possible stretch factors. The results exhibit a tradeoff between the efficiency of a routing scheme and its space requirements. We present almost tight upper and lower bounds for this tradeoff. Specifically, we prove that any routing scheme for general n-vertex networks that achieves a stretch factor k ≥ 1 must use a total of O(n1+1/2k+4) bits of routing information in the networks. This lower bound is complemented by a family H(k) of hierarchical routing schemes (for every fixed k ≥ 1), which guarantee a stretch factor of O(k), require storing a total of O(n1+1/k) bits of routing information in the network and name the vertices with O(log2n)-bit names.

Hypercube message routing in the presence of faults

Abstract: We discuss the problem of routing messages on hypercubes which have faulty processors and/or communication links. We are motivated by the belief that simple algorithms, operating under simple assumptions, can ensure high probabilities of successful message routing. In this paper, we consider the basic problem of routing a single message from an arbitrary source to an arbitrary destination. In our study, a fault is assumed to render the processor or link non-functional for purposes of communicating messages. As such, we may also consider communications hot spots as node faults, and our results also apply to routing in congested hypercubes.A framework for the analysis of fault tolerant routing schemes on a hypercube is presented. This framework includes differing routing schemes, routing information models and fault distribution models. The a priori probabilities of successful routing of a single, indivisible message under each of our possible sets of assumptions are calculated. Using random routing, under the one-step local information routing model, we show that the a priori probability of successful message routing is high even for an exceedingly large number of faults. We also analyze the behavior of sidetracking, a routing method which combines the concepts of local information and randomization. Using sidetracking, and in the one-step local information routing model, a message will be routed forward using random routing. If the message reaches a blocked processor (no non-faulty neighbors along a minimal path to the destination) it will be sent to a non-faulty neighbor, chosen uniformly at random from the set of non-faulty neighbors. We use simulation experiments to determine the performance of this routing scheme, analyzing the probability of successful routing and the expected path length of a routed message. The empirical performance of the sidetracking algorithms indicates strongly that, in the limit as the cube dimension grows larger and for a fixed probability of node failure, the probability of successful message routing is 100%.

Over-the-cell channel routing

Abstract: A common approach to the over-the-cell channel routing problem is to divide the problem into three steps: (1) routing over the cells; (2) choosing net segments; and (3) routing within the channel. It is shown that the first step can be reduced to the problem and finding a maximum independent set of a circle graph, and thus can be solved optimally in quadratic time. Also, it is shown that to determine an optimal choice of net segments in the second step is NP-hard in general, and an efficient heuristic algorithm for this step is presented. The third step can be carried out using a conventional channel router. On the basis of these theoretical results, an over-the-cell channel router that produces solutions which are better than the optimal two-layer channel routing solutions for all test examples is designed. The over-the-cell channel router also outperforms the over-the-cell channel router described by Y. Shiraishi and Y. Sakemi (ibid., vol.CAD-6, no.3, p.462-71, 1987). In particular, for Deutsch's difficult example, the solution yields a saving of 10.5% in channel routing area when compared with the optimal two-layer channel routing solution, and a saving of 15% in channel routing area when compared with the routing solution produced by the over-the-cell channel router. >

Vehicle routing and scheduling problems with time window constraints: efficient implementations of solution improvement procedures. vehicle routing: methods and studies. studies in management science and systems - volume 16

Abstract: A number of heuristic algorithms have been proposed for the vehicle routing and scheduling problem with time window constraints. These algorithms include both route construction and route improvement procedures. This paper extends branch exchange solution improvement procedures, well known from the standard vehicle routing literature, to vehicle routing and scheduling problems with time window constraints. We focus on efficient implementations of these procedures and present extensive computational results. The methods presented are completely robust in that significant reductions in running time are achieved without any degradation in the quality of the solution. (Author/TRRL)

A new algorithm for standard cell global routing

Abstract: The algorithm considers all of the interconnection nets in parallel. This produces superior results, since information about all of the nets is available throughout the global routing process. The global routing is formulated as finding the optimal spanning forest (a generalization of optimal spanning trees) on a graph that contains all of the interconnection information. The results of several theorems allow many nonoptimal connections to be pruned before the process begins. This approach successfully solves the net-ordering and congestion-prediction problems from which other approaches suffer. The algorithm was implemented as part of the DATools systems. The benchmarks from the Physical Design Workshop are used as part of the comparison suite. The algorithm achieves up to 11% area reduction compared to the previous global routing package used in the DATools systems and up to 17% reduction in the total channel density compared to the Timberwolf 4.2 package. In no case does the algorithm do worse than its competitors. >

Routing and broadcasting in faulty hypercube computers

Abstract: This paper examines routing and broadcasting algorithms for hypercube computers subject to node failures. First some simple message-passing algorithms are described which perform well with certain fault patterns, but poorly with others. The concept of an unsafe node is introduced to identify fault-free nodes that may cause communication difficulties in faulty hypercubes. It is then shown that by only using “feasible” paths that try to avoid unsafe nodes, routing and broadcasting can be substantially simplified. It is assumed that each active node is supplied with the fault status of all neighboring nodes within a specified radius k. A computationally efficient routing algorithm is presented which can route a message via a path of length no greater than p+2, where p is the minimum feasible distance from the source to the destination, provided that not all non-faulty nodes in the hypercube are unsafe, and k = 1. We further show that broadcasting can be achieved under the same fault conditions with only one more time unit than the fault-free case.

A new approach to three- or four-layer channel routing

Abstract: An approach to the three-layer or four-layer channel-routing problem is presented. A general technique that transforms a two-layer routing solution systematically into a three-layer routing solution is developed. The proposed router performs well in comparison with other three-layer channel routers proposed thus far. In particular, it provides a ten-track optimal solution for the famous Deutsch's difficult example, whereas other well-known three-layer channel routers required 11 or more tracks. The approach is extended to four-layer channel routing. Given any two-layer channel-routing solution without an unrestricted dogleg that uses w tracks, the router can obtain a four-layer routing solution using no more than w/2 tracks. A theoretical upper bound d/2+2 for arbitrary four-layer channel routing problems is also given. >

Optimal routing algorithms for mesh-connected processor arrays (extended abstract)

Abstract: We show that there is a randomized oblivious algorithm for routing any (partial) permutation on an n × n grid in 2n+O (log n) parallel communication steps. The queues will not grow larger than Θ(log n) with high probability. We then modify this to obtain a (non-oblivious) algorithm with the same running time such that the size of the queues is bounded by a constant with high probability. For permutations with locality, where each packet has to travel distance at most L in either the horizontal or the vertical direction, a generalization of the algorithm routes in time 3L+o(L), while the queue size remains bounded by Θ(log n) with high probability. Finally, we show that for a general class of oblivious deterministic routing strategies, Ω(n 2) time is required if we want to have constant size queues.

Adaptive packet routing in a hypercube

Abstract: All commercial hypercubes use fixed-path routing for packet switching. However, it has long been known that adaptive routing reduces packet delay by sending packets via less congested areas. Moreover, the hypercube topology contains many alternative, equal-length paths, suggesting the desirability of adaptive routing. Noting the importance of a communication system and the efficiency of adaptive routing, we investigate the effect of packet routing on communication latency and message throughput in a hypercube. As a feasibility study of adaptive routing, we selected four representative adaptive routing methods for testing on the Intel IPSC: NRCC routing, shortest queue, delta, and hybrid weighted routing. In NRCC routing, a single node, the network routing control center (NRCC), collects network status information and distributes routing tables to all other nodes. In contrast, shortest queue routing is fully distributed; each node selects the link with the shortest queue of outgoing messages that is the part of a shortest path to the destination node. Delta and hybrid weighted routing are hybrid schemes, combining centralized NRCC routing and distributed shortest queue routing. Extensive simulation studies and implementation confirm the superiority of adaptive routing to the fixed-path routing in commercial hypercubes. This result holds for a variety of traffic models, including high temporal locality and traffic surges.

Multi-pads, single layer power net routing in VLSI circuits

Abstract: An algorithm is presented for obtaining a planar routing of two power nets in building-block layout. In contrast to other works, more than one pad for each of the power nets is allowed. First, conditions are established to guarantee a planar routing. The algorithm consists of three parts, a top-down terminal clustering, a bottom-up topological path routing, and a wire-width calculation procedure. Because of the hierarchical nature of the algorithm, it is inherently fast. >

Decentralized adaptive routing for virtual circuit networks using stochastic learning automata

Abstract: The problem of routing virtual circuits according to dynamical probabilities in virtual-circuit packet-switched networks is considered. Queueing network models are introduced and performance measures are defined. A decentralized asynchronous adaptive routing methodology based on learning automata theory is presented. Every node in the network has a stochastic learning automaton as a router for every destination node. The routing probabilities that are assigned to the network paths are updated asynchronously on the basis of current network conditions. A learning algorithm suitable for routing is used. Some initial simulation experiments, for a simple network, show convergence to optimal routing. >

Permutation Channel Routing

Abstract: Most of the channel routing algorithms in the literature [Deut76, YoKu82, RiFi82, BuPe83, ReSS85] including the simulated annealing channel routers studied in Chapter 4 assume a model in which the pins on the two sides of the channel are fixed (both physically and logically.) Other models that reflect less stringent physical constraints have also been studied. In [GoCW83], it was assumed that only the relative ordering of the pins is fixed. The pins are allowed to “shift” horizontally. This model captures the possibility of expanding or contracting the dimensions of a cell. In [LeLi83] and [Leon86a], the discretionary channel routing problem in which only some of the pins in a given net need to be interconnected was studied. This model captures the possibility of having physically equivalent pins or duplicated pins in a cell. As expected, such flexibilities lead to better routing results, namely, fewer tracks are required for interconnection.

Smoothed perturbation analysis algorithm for a G/G/1 routing problem

Abstract: The smoothed perturbation analysis (SPA) algorithm is proposed for estimating the derivative of the mean delay with respect to the routing probability for a routing problem in data-communication networks. The algorithm requires minimum knowledge about the system and is very suitable for on-line optimization of clata-conimunication networks. It is shown that the SPA algorithm is unbiased.

Comparison of two bridge routing approaches

Abstract: Two routing algorithms proposed for a bridged LAN environment are examined. One is based on creating a spanning tree topology; the other takes a source routing approach. The features of the running environment and the functional requirements of bridge routing are identified, and the two approaches are compared. >

A multi-objective routing problem revisited

Abstract: A dynamic programming model is proposed for a multi-objective routing problem and is compared with the model proposed recently for this problem by Sancho.1

Connectivity biased channel construction and ordering for building-block layout

Abstract: A number of techniques are presented for the construction and ordering of routing channels for building-block layout. First, before the routing channels are defined the placement is modified such that proper routing space is assigned between the circuit blocks. Second, a channel graph is constructed on which the global routing will be performed. Finally, after the global routing a feasible routing order is assigned to the channels. In contrast to other works, the algorithms use both the geometrical data (the placement) and the topological data (the connectivity) to decide which channel structure should be chosen from the feasible set.

A Parallel Algorithm for Channel Routing

Abstract: We present an optimal NC algorithm for 2-layer channel routing of VLSI designs. Our routing algorithm achieves channel density and runs in O(logn) time using O(n) processors on an EREW P-RAM. The routing algorithm is a parallel version of the widely used Left-Edge Algorithm. It can be used to solve the maximum clique and the minimum coloring problem for interval graphs and the maximum independent set problem for co-interval graphs with optimal processor-time bounds. We give an optimizing extension to our algorithm that resolves column conflicts under certain weak conditions and runs in polylog time. The routing algorithm can easily be implemented on a multi-processor shared-memory machine so our solution has considerable practical value.

Space-efficient and fault-tolerant message routing in outerplanar networks

Abstract: The problem of designing space- and communication-efficient routing schemes for networks that experience faults is addressed. For any outerplanar network containing t faults, a succinct routing scheme is presented that uses O( alpha tn) space and communication to generate routings that are less than (( alpha +1)/( alpha -1))/sup t/ times longer than optimal, where alpha >1 is an odd-valued integer parameter. Thus, the routings can be tuned as desired, using a suitable amount of information. Efficient sequential and distributed algorithms are presented for setting up the routing schemes. >

Performance evaluation of a hierarchical hybrid adaptive routing algorithm for large scale computer communication networks

Abstract: A hierarchical hybrid adaptive routing algorithm (HHARA) is presented for dynamic large-scale computer communication networks (LSCCN). The performance of the proposed algorithm is evaluated and compared to that of nonhierarchical routing algorithms by simulation experiments on a 50-node network model. The major evaluation criteria are reliability, communication overhead, computation overhead, and average packet delay. A fixed routing algorithm, the most recent ARPANET routing algorithm, and HHARA are compared using simulation experiments. The simulation study indicates that HHARA makes a good balance between the reduction of routing database maintenance overhead, and the global routing capability as well as the local adaptivity to the network changes. >

Simple three-layer channel routing algorithms

Abstract: In this paper we present a simple three-layer assignment algorithm for planar layouts generated by a class of layout algorithms. This class of algorithms includes simple variations of the currently best algorithms for the three layer channel routing problem (CRP). More specifically, this class includes algorithms "equivalent" to the following algorithms (i–iii) developed by Mehlhorn, Preparata and Sarrafzadeh [7].

Hierarchical clustering with topology databases

Abstract: Dynamic routing in networks helps to provide efficient utilization of network resources. However, when networks are too large, the overhead introduced by dynamic routing consumes too much of network resources (processing, transmission capacity, and storage). To overcome this, researchers have investigated techniques to hierarchically organize networks and thereby reduce overhead. This paper introduces a new technique to organize routing information in large networks. A “radius database” provides optimal routing between frequent communicators. The combination of a “cluster database”, and a backbone, allows reasonable routing to all nodes. The paper details the information maintained at each node, describes distributed update algorithms to allow dynamic maintenance of the information, and indicates how to cluster networks to take advantage of this techniques. Simulation results support the efficacy of the technique.

Distributed load balancing

Abstract: Summary form only given. The authors solve a load balancing problem for parallel processors, given limited state information. The novelty of the problem is that the routing units at the parallel arrival streams of tasks have different and limited state information. This makes the problem a team problem of a distributed control problem. The engineering model for this problem consists of arrival streams of tasks, routing units and processors. The control problem is to synthesize an algorithm for the routing units. Both open-loop and closed-loop routing algorithms are considered. A performance analysis has been carried out for the case of two processors. >

An optimal two-copy routing scheme in a communication network

Abstract: The authors consider a static routing problem in a network with failure-prone links. Two copies of each externally generated message are sent from the source to the destination along two disjoint paths with the objective of reducing the delay resulting from retransmissions of unsuccessful packets. They formulate an optimal-routing problem using a suitable delay function. This results in a nonlinear programming problem of minimizing the delay over routing assignment under certain constraints. Specifically, they impose a disjoint-path constraint on the route assignment. This nonlinear program is solved by an iteration method incorporating a combinatorial algorithm. The solution converges to the global minimum for a convex objective function over a convex feasible region. >

On routing and performance comparison of techniques for packet-switched networks using learning automata

Abstract: Distributed adaptive routing algorithms with the ability to adaptively proportion traffic over several paths is proposed for packet-switched data networks. A learning automaton is situated at each node of the network where a routing decision must be made and directs traffic entering the node onto one of the outgoing links. Using network feedback, and automaton modifies its routing strategy to improve its link selections. This approach has the advantage over existing routing schemes of offering a simple and extremely practical feedback and updating policy. >

Message routing schemes in a hypercube machine

Abstract: The aim of this study is to determine efficient routing schemes for message passing in a hypercube machine. Two different algorithms are considered, namely static routing in which the path of a message is predetermined by the addresses of the source and destination nodes, and dynamic routing where the decision as to the next node in the path is made by the current node on the basis of local information regarding queue lengths. In addition, various different prioritization schemes are compared for both static and dynamic routing. The results show that dynamic routing can be up to twice as efficient as static routing, provided priority is given to messages which have only a few hops to traverse or were transmitted early in the computation sequence.