Showing papers on "Routing (electronic design automation) published in 1999"

An improved Ant System algorithm for theVehicle Routing Problem

Abstract: The Ant System is a distributed metaheuristic that combines an adaptive memory with alocal heuristic function to repeatedly construct solutions of hard combinatorial optimizationproblems. In this paper, we present an improved ant system algorithm for the Vehicle RoutingProblem with one central depot and identical vehicles. Computational results on fourteenbenchmark problems from the literature are reported and a comparison with five othermetaheuristic approaches for solving Vehicle Routing Problems is given.

QoS routing in networks with inaccurate information: theory and algorithms

Abstract: This paper investigates the problem of routing flows with quality-of-service (QoS) requirements through one or more networks, when the information available for making such routing decisions is inaccurate. Inaccuracy in the information used in computing QoS routes, e.g., network state such as link and node metrics, arises naturally in a number of different environments that are reviewed in the paper. The goal is to determine the impact of such inaccuracy on the ability of the path-selection process to successfully identify paths with adequate available resources. In particular, we focus on devising algorithms capable of selecting path(s) that are most likely to successfully accommodate the desired QoS, in the presence of uncertain network state information for the purpose of the analysis, we assume that this uncertainty is expressed through probabilistic models, and we briefly discuss sample cases that can give rise to such models. We establish that the impact of uncertainty is minimal for flows with only bandwidth requirements, but that it makes path selection intractable when end-to-end delay requirements are considered. For this latter case, we provide efficient solutions for special cases of interest and develop useful heuristics.

A Survey of Virtual Topology Design Algorithms for Wavelength Routed Optical Networks

Abstract: In the past few years, there has been growing interest in wide area ``All Optical Networks'''' with {\em wavelength division multiplexing\/} (WDM), using {\em wavelength routing}. Due to the huge bandwidth inherent in optical fiber, and the use of WDM to match user and network bandwidths, the wavelength routing architecture is an attractive candidate for future backbone transport networks. A {\em virtual topology\/} over a WDM WAN consists of clear channels between nodes called {\em lightpaths}, with traffic carried from source to destination without electronic switching ``as far as possible'''', but some electronic switching may be performed. Virtual topology design aims at combining the best of optical switching and electronic routing abilities. Designing a virtual topology on a physical network consists of deciding the lightpaths to be set up in terms of their source and destination nodes and wavelength assignment. In this survey we first describe the context and motivations of the virtual topology design problem. We provide a complete formulation of the problem, describe and compare the formulations and theoretical results as well as algorithms, heuristics and some results in the current literature in the field. The reconfigurability issue, which is another attractive characteristic of optical networks, is also discussed and the literature surveyed. This survey is restricted to transport networks with wavelength routing. Similar virtual topology problems also arise in multihop broadcast local area optical networks, but this work does not directly apply to them and corresponding literature is not included in this survey. This survey also relates to the design of a static topology, not one in which individual lightpaths are set up and torn down in response to traffic demand.

Rule based ip data processing

Abstract: A apparatus and method that provides a routing engine for processing data packets based upon certain rules that are compiled and applied real-time via a just-in-time (JIT) compiler, a runtime compiler, or the like. The routing engine parses and analyzes an incoming IP flow. A set of rules are developed and stored for use by the JIT. The rules establish a set of patterns, and the incoming data is compared to those patterns. If certain patterns are detected, then the associated action established by the rule is applied to the processing of the data packet. Packets are classified according to any rule, as applied to any packet, as early as possible in the process (i.e. first or second stage of process), with the route lookup and packet attribute processes performed in parallel. Data packets might be assigned or mapped to various traffic service levels. Traffic types and priorities, as well as service levels, can be mapped onto existing QoS/CoS definitions and assignments. The data packets can be altered or modified as a result of the detected patterns. Data packets can also be discarded or dropped if the detected patterns and associated rule indicate such a desire. The apparatus and method might be implemented as a hardware and software configuration. A software configuration might also be loaded into existing router hardware.

Optical network design and restoration

Abstract: The explosion of data traffic and the availability of enormous bandwidth via dense wavelength division multiplexing (DWDM) and optical amplifier (OA) technologies make it important to study optical layer networking and restoration. This paper is concerned with fast distributed restoration and provisioning for generic mesh-based optical networks. We consider two problems of practical importance: determining the best restoration route for each wavelength demand, given the network topology and the capacities and primary routes of all demands, and determining primary and restoration routes for each wavelength demand to minimize network capacity and cost. The approach we propose for both problems is based on precomputing. For each problem, we describe specific algorithms used for computing routes. We also describe endpoint-based failure detection, message flows, and cross-connect actions for execution of fast restorations. Finally, we report test results for large carrier-scale networks that include both the computational performance of the optimization algorithms and the restoration speed obtained by simulation. Our results indicate that subsecond restoration, high capacity efficiency, and scalability can be achieved without fault isolation and with moderate processing. We also discuss methods for scaling algorithms to problems with very large numbers of demands. The wavelength routing and restoration algorithms, the failure detection, and the message exchange and activation architectures we propose are collectively known as WaveStar™ advanced routing platform.

A unified routing scheme for ad-hoc internetworking

Abstract: Routing table update messsages that include both network-level and link-level addresses of nodes of a computer network are exchanged among the nodes of the computer network. Further, a routing table maintained by a first one of the nodes of the computer network may be updated in response to receiving one or more of the update messages. The shortest distance to the destination node may be determined according to one or more link-state and/or node-state metrics regarding communication links and nodes along the path to the destination node. Also, the nodal characteristics of the nodes of the computer system may be exchanged between neighbor nodes, prior to updating the routing table.

Online Routing in Triangulations

Abstract: We consider online routing strategies for routing between the vertices of embedded planar straight line graphs. Our results include (1) two deterministic memoryless routing strategies, one that works for all Delaunay triangulations and the other that works for all regular triangulations, (2) a randomized memoryless strategy that works for all triangulations, (3) an O(1) memory strategy that works for all convex subdivisions, (4) an O(1) memory strategy that approximates the shortest path in Delaunay triangulations, and (5) theoretical and experimental results on the competitiveness of these strategies.

An orthogonal genetic algorithm for multimedia multicast routing

Abstract: Many multimedia communication applications require a source to send multimedia information to multiple destinations through a communication network. To support these applications, it is necessary to determine a multicast tree of minimal cost to connect the source node to the destination nodes subject to delay constraints on multimedia communication. This problem is known as multimedia multicast routing and has been proved to be NP-complete. The paper proposes an orthogonal genetic algorithm for multimedia multicast routing. Its salient feature is to incorporate an experimental design method called orthogonal design into the crossover operation. As a result, it can search the solution space in a statistically sound manner and it is well suited for parallel implementation and execution. We execute the orthogonal genetic algorithm to solve two sets of benchmark test problems. The results indicate that for practical problem sizes, the orthogonal genetic algorithm can find near optimal solutions within moderate numbers of generations.

Interconnect Analysis and Synthesis

Abstract: From the Publisher: State-of-the-art methods and current perspectives on interconnect The irrepressible march toward smaller and faster integrated circuits has made interconnect a hot topic for semiconductor research. The effects of wire size, topology construction, and network design on system performance and reliability have all been thoroughly investigated in recent years. Interconnect Analysis and Synthesis provides CAD researchers and engineers with powerful, state-of-the-art tools for the analysis, design, and optimization of interconnect. It brings together a wealth of information previously scattered throughout the literature, explaining in depth available analysis techniques and presenting a range of CAD algorithms for synthesizing and optimizing interconnect. Along with examples and results from the semiconductor industry and 150 illustrations, this practical work features: *Models for interconnect as well as devices and the impact of scaling trends *Modern analysis techniques, from matrix reduction and moment matching to transmission-line analysis *An overview of the effects of inductance on on-chip interconnect *Flexible CAD algorithms that can be generalized for different needs, from buffer insertion to wire sizing to routing topology *Emphasis on realistic problem formulations, addressing key design tradeoffs such as those between area and performance

The design of a SRAM-based field-programmable gate array-Part II: Circuit design and layout

Abstract: For Pt.I see ibid., vol.7, pp.191-7 (1999). Field-programmable gate arrays (FPGA's) are now widely used for the implementation of digital systems, and many commercial architectures are available. Although the literature and data books contain detailed descriptions of these architectures, there is very little information on how the high-level architecture was chosen and no information on the circuit-level or physical design of the devices. In Part I of this paper, we described the high-level architectural design of a static random-access memory programmable FPGA. This paper will address the circuit-design issues through to the physical layout. We address area-speed tradeoffs in the design of the logic block circuits and in the connections between the logic and the routing structure. All commercial FPGA designs are done using full-custom hand layout to obtain absolute minimum die sizes. This is both labor and time intensive. We propose a design style with a minitile that contains a portion of all the components in the logic tile, resulting in less full-custom effort. The minitile is replicated in a 4/spl times/4 array to create a macro tile. The minitile is optimized for layout density and speed, and is customized in the array by adding appropriate vias. This technique also permits easy changing of the hard-wired connections in the logic block architecture and the segmentation length distribution in the routing architecture.

A path availability model for wireless ad-hoc networks

Abstract: Ad-hoc networks are expected to play an important role in future commercial and military communications systems. As such, scalable routing strategies capable of supporting greater user mobility and a wide range of applications are needed. This paper proposes a novel routing metric, which defines a probabilistic measure of the availability of network paths that are subject to link failures caused by node mobility in ad-hoc networks. It is shown how this measure can be used to select more stable paths and reduce the routing overhead caused by node mobility. A mobility model is first proposed and used to characterize the movement of ad-hoc network nodes. This model is then used to derive expressions for link and path availability. Finally, simulation results are reported which validate the proposed analytical model.

Analysis of multi-path routing

Abstract: In connection-oriented networks, resource reservations must be made before data can be sent along a route. For short or bursty connections, a selected route must have the required resources to ensure appropriate communication with regard to desired quality-of-service (QoS). For example, in ATM networks, the route setup process considers only links with sufficient resources and reserves these resources while it advances toward the destination. The same concern for QoS routing appears in datagram networks such as the Internet, when applications with QoS requirements need to reserve resources along pinned routes. In this paper, we analyze the performance of multi-path routing algorithms and compare them to single-path reservation that might be persistent, i.e., retry after a failure. The analysis assumes that the routing process reserves resources while it advances toward the destination, thus there is a penalty associated with a reservation that cannot be used. Our analysis shows that while multi-path reservation algorithms perform comparably to single-path reservation algorithms, either persistent or not, the connection-establishment time for multi-path reservation is significantly lower. Thus, multi-path reservation becomes an attractive alternative for interactive applications such as World Wide Web browsing.

An Evaluation of Routing and Volume‐based Storage Policies in an Order Picking Operation

Abstract: Order picking, the assembly of a customer's order from items in storage, is an essential link in the supply chain and is the major cost component of warehousing. The critical issue is to simultaneously reduce the cost and increase the speed of the order picking activity. This study departs from the limited prior research that focused on either routing of workers or storage of warehoused items. The main objectives are to (1) evaluate various routing heuristics versus an optimal routine in a volume-based storage environment, (2) propose several methods of implementing volume-based storage, and (3) examine the interaction of the routing and storage policies under different operating conditions of pick list size and demand skewness. The experimental results show statistically significant differences in the mean route distance for the routing policies, storage policies, and their interactions. Further testing indicates that the choice of certain routing and storage policies in combination can result in increased picking efficiency.

Maximizing text-mining performance

Abstract: The authors' adaptive resampling approach surpasses previous decision-tree performance and validates the effectiveness of small, pooled local dictionaries. They demonstrate their approach using the Reuters-21578 benchmark data and a real-world customer E-mail routing system.

A new approach to on-demand loop-free multipath routing

Abstract: We present and verify ROAM, an on-demand routing algorithm that maintains multiple loop-free paths to destinations. Each router maintains entries only for those destinations for which data flows through the router which reduces storage space requirements and the amount of bandwidth needed to maintain correct routing tables. In ROAM, routes are established and maintained on demand using diffusing computations. A router does not send updates for active destinations, unless its distance to them increases beyond a given threshold. ROAM maintains a state that informs routers when a destination is unreachable and prevents routers from sending unnecessary search packets attempting to find paths to an unreachable destination. ROAM is shown to converge in a finite time after an arbitrary sequence of topological changes and is shown to be loop-free at every instant. The time and communication complexities of ROAM are analyzed.

FPGA routing architecture: segmentation and buffering to optimize speed and density

Abstract: In this work we investigate the routing architecture of FPGAs, focusing primarily on determining the best distribution of routing segment lengths and the best mix of pass transistor and tri-state buffer routing switches. While most commercial FPGAs contain many length 1 wires (wires that span only one logic block) we find that wires this short lead to FPGAs that are inferior in terms of both delay and routing area. Our results show instead that it is best for FPGA routing segments to have lengths of 4 to 8 logic blocks. We also show that 50% to 80% of the routing switches in an FPGA should be pass transistors, with the remainder being tri-state buffers. Architectures that employ the best segmentation distributions and the best mixes of pass transistor and tri-state buffer switches found in this paper are not only 11% to 18% faster than a routing architecture very similar to that of the Xilinx XC4000X but also considerably simpler. These results are obtained using an architecture investigation infrastructure that contains a fully timing-driven router and detailed area and delay models.

Cooperating Mobile Agents for Dynamic Network Routing

Abstract: Contemporary computer networks are heterogeneous; even a single network consists of many kinds of processors and communications channels. Networks are also inherently decentralized; capability is scattered across the system. But few system design methodologies embrace or even acknowledge these complexities. New methods and approaches are required if next-generation networks are to be configured, administered and utilized to their full potentials. In our research at the MIT Media Laboratory we are building systems that use mobile software agents to manage complex real-world networks. In this chapter we describe a strategy for using a collection of cooperating mobile agents to solve routing problems for dynamic, peer-to-peer networks.

Routing with end-to-end QoS guarantees in broadband networks

Abstract: We consider routing schemes for connections with end-to-end delay requirements, and investigate several fundamental problems. First, we focus on networks which employ rate-based schedulers and, hence, map delay guarantees into nodal rate guarantees, as done with the guaranteed service class proposed for the Internet. We consider first the basic problem of identifying a feasible route for the connection, for which a straightforward yet computationally costly solution exists. Accordingly, we establish several approximation schemes that offer substantially lower computational complexity. We then consider the more general problem of optimizing the route choice in terms of balancing loads and accommodating multiple connections, for which we formulate and validate several optimal algorithms. We discuss the implementation of such schemes in the context of link-state and distance-vector protocols. Next, we consider the fundamental problem of constrained path optimization. This problem, typical of quality of service routing, is NP-hard. While standard approximation methods exist, their complexity may often be prohibitive in terms of scalability. Such approximations do not make use of the particular properties of large-scale networks, such as the face that the path selection process is typically presented with a hierarchical, aggregated topology. By exploiting the structure of such topologies, we obtain an /spl epsiv/-optimal algorithm for the constrained shortest-path problem, which offers a substantial improvement in terms of scalability.

Multi-agent pseudo-differential signaling scheme

Abstract: A circuit for reducing the effect of noise on signals. The circuit includes a plurality of information signal lines having a substantially matched routing, and a reference voltage line having a routing substantially matched to the routing of the plurality of information signal lines. The circuit further includes a transmitting agent coupled to the plurality of information signal lines and to the reference voltage signal line, including a noise coupling circuit for coupling noise from the transmitting agent to the reference voltage line.

Packet classification using tuple space search

Abstract: Routers must perform packet classification at high speeds to efficiently implement functions such as firewalls and QoS routing. Packet classification requires matching each packet against a databas...

The impact of routing and storage policies on warehouse efficiency

Abstract: Order picking, the activity by which a number of goods are retrieved from a warehousing system to satisfy a number of customer orders, is an essential link in the supply chain and is the major cost component of warehousing. The critical issue is to simultaneously reduce the cost and increase the speed of the order picking activity. The main objectives of this paper are: evaluate various routing heuristics and an optimal routine in a volume‐based and random storage environment; compare the performance of volume‐based storage to random storage; and examine the impact of travel speed and picking rates on routing and storage policy performance. The experimental results show the solution gap between routing heuristics and optimal routing is highly dependent on the travel speed and picking rate, the storage policy, and the size of the pick list. In addition, volume‐based storage produced significant savings over random storage, but again these savings are dependent on the travel speed and picking rate.

Genetic Algorithms for Vlsi Design, Layout & Test Automation

Abstract: This book provides details about some of the EDA applications where GAs have been used. These applications include partitioning, automatic placement and routing, technology mapping for FPGAs, automatic test generation, and power estimation. One chapter is devoted to each of these topics. The objective is to provide examples where GAs have been successfull applied in the past so that the reader will be able to apply similar techniques in solving his/her own problems.

A routing vector method (RVM) for routing in Bluetooth scatternets

Abstract: Bluetooth is a promising new technology for short range wireless connectivity between mobile devices. Initially, Bluetooth will be used as a replacement for point to-(multi)point cables. However, in due course of time, solutions for forming multihop ad hoc networks over Bluetooth (referred to as scatternets) will be needed. In this paper, we explore the design space of routing protocols over Bluetooth scatternets. We argue that ad hoc routing protocols for Bluetooth must make a different set off design compromises compared to those being developed by the MANET working group. These differences result primarily from the specific characteristics of the Bluetooth physical and link layer. Our proposed routing method is based on the concept of route vector, which is an efficient method for encoding source route paths in Bluetooth scatternets. We describe the protocols for route discovery and packet forwarding. Our design illustrates three main design compromises, namely minimization of soft-state, protocol simplicity, and bandwidth conservation, all of are crucial for efficient operation over small size Bluetooth scatternets.

Satisfiability-based layout revisited: detailed routing of complex FPGAs via search-based Boolean SAT

Abstract: 1. ABSTRACT lier BDD-based methods. Boolean-based routing transforms the geometric FPGA routing task into a single, large Boolean equation with the property that any assignment of input variables that “satisfies” the equation (that renders equation identically “1”) specifies a valid routing. The formulation has the virtue that it considers all nets simultaneously, and the absence of a satisfying assignment implies that the layout is unroutable. Initial Boolean-based approaches to routing used Binary Decision Diagrams (BDDs) to represent and solve the layout problem. BDDs, however, limit the size and complexity of the FPGAs that can be routed, leading these approaches to concentrate only on individual FPGA channels. In this paper, we present a new search-based Satisfiability (SAT) formulation that can handle entire FPGAs, routing all nets concurrently. The approach relies on a recently developed SAT engine (GRASP) that uses systematic search with conflict-directed non-chronological backtracking, capable of handling very large SAT instances. We present the first comparisons of search-based SAT routing results to other routers, and offer the first evidence that SAT methods can actually demonstrate the unroutability of a layout. Preliminary experimental results suggest that this approach to FPGA routing is more viable than ear1.1

The end-to-end effects of Internet path selection

Abstract: The path taken by a packet traveling across the Internet depends on a large number of factors, including routing protocols and per-network routing policies. The impact of these factors on the end-t...

Apparatus and method for calendar based call routing

Abstract: A telecommunications system is provided whereby call routing may be based on a pre-programmed calendar of time-date associations. Moreover, the routing may be selective, based on caller-identification information. In particular, when a call arrives at a messaging server (804), such as a PBX or TOL server, a LAN database is checked. The LAN database points to a calendar (916, 918) corresponding to the user. The calendar (918) is queried to determine the user's location. The caller ID information is checked to determine whether the caller is authorized for forwarding. If so, the call is forwarded based on the calendar.

Self-directed routable electronic form system and method

Abstract: This invention provides for a self-directed routable electronic form generation system and method where each user in the process defines the next, or all the subsequent user routing. The invention resides in providing rules and guidelines that define routing to exist completely within the electronic form itself. Residing in the electronic form these routing rules are dynamically changed based on data input to the form, providing visual clues to the routing based on that input. The present invention generates in the approver's view of the form appropriate visual elements corresponding with allowable actions of this subsequent viewer. The present invention also provides visual clues as to the next routing destination based on the electronics form current fill-in data, or based on any changes the approver makes to fill-in data, all without server interaction. This sequence continues until the electronics “form flow” is complete and an end point is reached.