Showing papers on "Routing (electronic design automation) published in 2000"

A Review of Routing and Wavelength Assignment Approaches for Wavelength- Routed Optical WDM Networks

Abstract: This study focuses on the routing and WavelengthAssignment (RWA) problem in wavelength-routed optical WDM networks. Most of the attention is devoted to such networks operating under the wavelength-continuity constraint, in which lightpaths are set up for connection requests between node pairs, and a single lightpath must occupy the same wavelength on all of the links that it spans. In setting up a lightpath, a route must be selected and a wavelength must be assigned to the lightpath. If no wavelength is available for this lightpath on the selected route, then the connection request is blocked. We examine the RWA problem and review various routing approaches and wavelengthassignment approaches proposed in the literature. We also briefly consider the characteristics of wavelength-converted networks (which do not have the wavelength-continuity constraint), and we examine the associated research problems and challenges. Finally, we propose a new wavelengthassignment scheme, called Distributed Relative Capacity Loss (DRCL), which works well in distributed-controlled networks, and we demonstrate the performance of DRCL through simulation.

GPSR : Greedy Perimeter Stateless Routing for Wireless

Abstract: We present Greedy Perimeter Stateless Routing (GPSR), a novel routing protocol for wireless datagram networks that uses the positions of routers and a packet’s destination to make packet forwarding decisions. GPSR makes greedy forwarding decisions using only information about a router’s immediate neighbors in the network topology. When a packet reaches a region where greedy forwarding is impossible, the algorithm recovers by routing around the perimeter of the region. By keeping state only about the local topology, GPSR scales better in per-router state than shortest-path and ad-hoc routing protocols as the number of network destinations increases. Under mobility’s frequent topology changes, GPSR can use local topology information to find correct new routes quickly. We describe the GPSR protocol, and use extensive simulation of mobile wireless networks to compare its performance with that of Dynamic Source Routing. Our simulations demonstrate GPSR’s scalability on densely deployed wireless networks.

Greedy Perimeter Stateless Routing for Wireless Networks

Abstract: We present Greedy Perimeter Stateless Routing (GPSR), a novel routing protocol for wireless datagram networks that uses the positions of routers and a packet’s destination to make packet forwarding decisions. GPSR makes greedy forwarding decisions using only information about a router’s immediate neighbors in the network topology. When a packet reaches a region where greedy forwarding is impossible, the algorithm recovers by routing around the perimeter of the region. By keeping state only about the local topology, GPSR scales better in per-router state than shortest-path and ad-hoc routing protocols as the number of network destinations increases. Under mobility’s frequent topology changes, GPSR can use local topology information to find correct new routes quickly. We describe the GPSR protocol, and use extensive simulation of mobile wireless networks to compare its performance with that of Dynamic Source Routing. Our simulations demonstrate GPSR’s scalability on densely deployed wireless networks.

Analysis of an Equal-Cost Multi-Path Algorithm

Abstract: Equal-cost multi-path (ECMP) is a routing technique for routing packets along multiple paths of equal cost. The forwarding engine identifies paths by next-hop. When forwarding a packet the router must decide which next-hop (path) to use. This document gives an analysis of one method for making that decision. The analysis includes the performance of the algorithm and the disruption caused by changes to the set of next-hops.

Can recursive bisection alone produce routable placements

Abstract: This work focuses on congestion-driven placement of standard cells into rows in the fixed-die context. We summarize the state-of-the-art after two decades of research in recursive bisection placement and implement a new placer, called Capo, to empirically study the achievable limits of the approach. From among recently proposed improvements to recursive bisection, Capo incorporates a leading-edge multilevel min-cut partitioner [7], techniques for partitioning with small tolerance [8], optimal min-cut partitioners and end-case min-wirelength placers [5], previously unpublished partitioning tolerance computations, and block splitting heuristics. On the other hand, our “good enough” implementation does not use “overlapping” [17], multi-way partitioners [17, 20], analytical placement, or congestion estimation [24, 35]. In order to run on recent industrial placement instances, Capo must take into account fixed macros, power stripes and rows with different allowed cell orientations. Capo reads industry-standard LEF/DEF, as well as formats of the GSRC bookshelf for VLSI CAD algorithms [6], to enable comparisons on available placement instances in the fixed-die regime.Capo clearly demonstrates that despite a potential mismatch of objectives, improved mincut bisection can still lead to improved placement wirelength and congestion. Our experiments on recent industrial benchmarks fail to give a clear answer to the question in the title of this paper. However, they validate a series of improvements to recursive bisection and point out a need for transparent congestion management techniques that do not worsen the wirelength of already routable placements. Our experimental flow, which validates fixed-die placement results by violation-free detailed auto-routability, provides a new norm for comparison of VLSI placement implementations.

Internet Routing Architectures

Abstract: I. THE CONTEMPORARY INTERNET. 1. Evolution of the Internet. 2. ISP Services and Characteristics. 3. IP Addressing and Allocation Techniques. II. ROUTING PROTOCOL BASICS. 4. Interdomain Routing Basics. 5. Border Gateway Protocol Version 4. III. EFFECTIVE INTERNET ROUTING DESIGNS. 6. Tuning BGP Capabilities. 7. Redundancy, Symmetry, and Load Balancing. 8. Controlling Routing Inside the Autonomous System. 9. Controlling Large-Scale Autonomous Systems. 10. Designing Stable Internets. IV. INTERNET ROUTING DEVICE CONFIGURATION. 11. Configuring Basic BGP Functions and Attributes. 12. Configuring Effective Internet Routing Policies. V. APPENDIXES. Appendix A: BGP Command Reference. Appendix B: References for Further Study. Appendix C: BGP Outbound Route Filter (ORF). Appendix D: Multiprotocol BGP (MBGP).

Minimum interference routing of bandwidth guaranteed tunnels with MPLS traffic engineering applications

Abstract: This paper presents new algorithms for dynamic routing of bandwidth guaranteed tunnels, where tunnel routing requests arrive one by one and there is no a priori knowledge regarding future requests. This problem is motivated by the service provider needs for fast deployment of bandwidth guaranteed services. Offline routing algorithms cannot be used since they require a priori knowledge of all tunnel requests that are to be rooted. Instead, on-line algorithms that handle requests arriving one by one and that satisfy as many potential future demands as possible are needed. The newly developed algorithms are on-line algorithms and are based on the idea that a newly routed tunnel must follow a route that does not "interfere too much" with a route that may he critical to satisfy a future demand. We show that this problem is NP-hard. We then develop path selection heuristics which are based on the idea of deferred loading of certain "critical" links. These critical links are identified by the algorithm as links that, if heavily loaded, would make it impossible to satisfy future demands between certain ingress-egress pairs. Like min-hop routing, the presented algorithm uses link-state information and some auxiliary capacity information for path selection. Unlike previous algorithms, the proposed algorithm exploits any available knowledge of the network ingress-egress points of potential future demands, even though the demands themselves are unknown. If all nodes are ingress-egress nodes, the algorithm can still be used, particularly to reduce the rejection rate of requests between a specified subset of important ingress-egress pairs. The algorithm performs well in comparison to previously proposed algorithms on several metrics like the number of rejected demands and successful rerouting of demands upon link failure.

Arc Routing : Theory, Solutions and Applications

Abstract: Preface Contributing Authors 1 A Historical Perspective on Arc Routing HA Eiselt, G Laporte Part I Theory: 2 Traversing Graphs: The Eulerian and Hamiltonian Theme h Fleischner 3 Matching: Arc Routing and Solution Connection U Derigs 4 Arc Routing: Complexity and Approximability M Dror 5 Chinese Postman and Euler Tour Problems in Bi-directed Graphs ELJohnson Part II Solutions: 6 Polyhedral Theory for Arc Routing Problems RW Eglese, AN Letchford 7 Linear Programming Based Methods for Solving Arc Routing Problems E Benavent, et al 8 Transformations and Exact Node Routing Solutions by Column Generation M Dror, A Langevin 9 Heuristic Algorithms A Hertz, M Mittaz Part III Applications: 10 Roadway Snow and Ice Control JF Campbell, A Langevin 11 Scheduling of Local Delivery Carrier Routes for the United States Postal Service L Bodin, L Levy 12 Livestock Feed Distribution and Arc Traversal Problems M Dror, et al

New dynamic algorithms for shortest path tree computation

Abstract: The open shortest path first (OSPF) and IS-IS routing protocols widely used in today's Internet compute a shortest path tree (SPT) from each router to other routers in a routing area Many existing commercial routers recompute an SPT from scratch following changes in the link states of the network Such recomputation of an entire SPT is inefficient and may consume a considerable amount of CPU time Moreover, as there may coexist multiple SPTs in a network with a set of given link states, recomputation from scratch causes frequent unnecessary changes in the topology of an existing SPT and may lead to routing instability We present new dynamic SPT algorithms that make use of the structure of the previously computed SPT Besides efficiency, our algorithm design objective is to achieve routing stability by making minimum changes to the topology of an existing SPT (while maintaining shortest path property) when some link states in the network have changed We establish an algorithmic framework that allows us to characterize a variety of dynamic SPT algorithms including dynamic versions of the well-known Dijkstra, Bellman-Ford, D'Esopo-Pape algorithms, and to establish proofs of correctness for these algorithms in a unified way The theoretical asymptotic complexity of our new dynamic algorithms matches the best known results in the literature

Interconnect analysis and synthesis

Abstract: Interconnect Models. Device Models. Interconnect Analysis. Inductance and Inductive Coupling for On--chip Interconnect. Synthesis: Overview and Static Topology Optimization. Global Routing Topology Synthesis. Optimization of Multi--Source Nets. Timing Driven Maze Routing.

A framework for scalable global IP-anycast (GIA)

Abstract: This paper proposes GIA, a scalable architecture for global IP-anycast. Existing designs for providing IP-anycast must either globally distribute routes to individual anycast groups, or confine each anycast group to a pre-configured topological region. The first approach does not scale because of excessive growth in the routing tables, whereas the second one severely limits the utility of the service. Our design scales by dividing inter-domain anycast routing into two components. The first component builds inexpensive default anycast routes that consume no bandwidth or storage space. The second component, controlled by the edge domains, generates enhanced anycast routes that are customized according to the beneficiary domain's interests. We evaluate the performance of our design using simulation, and prove its practicality by implementing it in the Multi-threaded Routing Toolkit.

High performance switch fabric element and switch systems

Abstract: A high performance switch fabric element and flexible link interconnection topologies and frame addressing techniques therefor are disclosed. The fabric element, which may be a 16 port ASIC with internal steerable interconnection among all ports. The fabric element ports each have a unique local routing table, thereby avoiding the need for a global routing table for ports as is provided in the prior art. This also permits addressing and routing from port to port within the fabric element without need for look-up references from off the fabric element, thereby contributing to speed. The fabric element can be used in multiples interconnected by unique link interconnection techniques including cascade, mesh, microstaging, and combinations thereof. These link interconnection techniques provide unique switch topologies that permit high performance switching chassis or network box having a significantly larger number of ports than is achievable with the prior art techniques.

Time-varying network tomography: router link data

Abstract: In a computer network, the traffic matrix or the origin-destination (OD) byte counts are important statistics needed for design, routing, configuration debugging, monitoring and pricing However, they are not easily available For a fixed routing scheme, a statistical inverse algorithm is proposed and validated to estimate the traffic matrix from the easily collectable link counts which are aggregations of the origin-destination counts

A safe path vector protocol

Abstract: An IP routing protocol is safe if it is guaranteed to converge in the absence of network topology changes. BGP, currently the only interdomain routing protocol employed on the Internet, is not safe in this sense. It may seem that the source of BGP's potential divergence is inherent in the requirements for any interdomain routing protocol-policy-based metrics must be allowed to override distance-based metrics, and each autonomous system must be allowed to independently define its routing policies with little or no global coordination. In this paper we present a simple path vector protocol (SPVP) that captures the underlying semantics of BGP by abstracting away all nonessential details. We then add a dynamically computed attribute to SPVP routing messages, called the route history. Protocol oscillations caused by policy conflicts produce routes whose histories contain cycles. These cycles identify the policy conflicts and the autonomous systems involved. SPVP is made safe by automatically suppressing routes whose histories contain cycles. We discuss how this safe SPVP can be used in the design of a safe BGP.

A Lower Bound for the Split Delivery Vehicle Routing Problem

Abstract: In this paper we consider the Split Delivery Vehicle Routing Problem (SDVRP), a relaxation of the known Capacitated Vehicle Routing Problem (CVRP) in which the demand of any client can be serviced by more than one vehicle. We define a feasible solution of this problem, and we show that the convex hull of the associated incidence vectors is a polyhedron ( PSDVRP), whose dimension depends on whether a vehicle visiting a client must service, or not, at least one unit of the client demand. From a partial and linear description ofPSDVRP and a new family of valid inequalities, we develop a lower bound whose quality is exhibited in the computational results provided, which include the optimal resolution of some known instances--one of them with 50 clients. This instance is, as far as we know, the biggest one solved so far.

A Survey of Algorithms for Convex Multicommodity Flow Problems

Abstract: Routing problems appear frequently when dealing with the operation of communication or transportation networks. Among them, the message routing problem plays a determinant role in the optimization of network performance. Much of the motivation for this work comes from this problem which is shown to belong to the class of nonlinear convex multicommodity flow problems. This paper emphasizes the message routing problem in data networks, but it includes a broader literature overview of convex multicommodity flow problems. We present and discuss the main solution techniques proposed for solving this class of large-scale convex optimization problems. We conduct some numerical experiments on the message routing problem with four different techniques.

A global wiring paradigm for deep submicron design

Abstract: Global interconnect is commonly regarded as a key potential bottleneck to the advancing performance of high-speed integrated circuits. Our previous work has suggested that local interconnect effects can be managed through a deep submicron design hierarchy that uses 50000 to 100000 gate modules as primitive building blocks. The primary goal of this paper is to examine global interconnect effects, within such a design hierarchy, to determine if there are any significant roadblocks which will prevent National Technology Roadmap for Semiconductors (NTRS) performance expectations from being met. Specifically, the issues of global resistance-capacitance delay, signal time-of-flight, inductance, clock and power distribution, and noise are studied. Results indicate that, while global clock frequencies will necessarily he lower than local clock speeds, NTRS expectations should be attainable to the 50 nm technology generation. Achieving these high clock speeds (10 GHz local clock) will be aided by the use of a newly proposed routing hierarchy which limits interconnect effects at each level of a design (local, isochronous, and global).

Server and method for routing messages to achieve unified communications

Abstract: A server routes one's incoming messages to his/her communication devices according to his/her routing preferences, and modifies the messages as needed. For example, the server can route an incoming page to one's email account and, if necessary, modify the page so that it is compatible with the email client. Thus, the server enables a number of diverse features such as: selection of routing topology (direct or indirect), translation of network restrictions, conditioning a synchronous communication for reception by an asynchronous device, message encryption, and callback or 'buddy list' services.

Enterprise contact server with enhanced routing features

Abstract: The present invention is an Enterprise Contact Server (100) that enables customers to submit call-back requests to agents (13) located at any one of a plurality of call centers (116) via the Internet (32), or virtually any other communications technology available.

Design, implementation and performance of a content-based switch

Abstract: In this paper, we share our experience in designing and building a content-based switch which we call L5. In addition to the layer 2-3-4 information available in the packet, a content-based switch uses application level information to route traffic in the network. Making routing decisions based on information contained in the payload is not a new idea. In fact application level proxies which are functionally equivalent to a content-based switch, have been around for years. Our contribution is in combining the functionalities of an application level proxy with the data handling capabilities of a switch into a single system. In this paper, we describe the architecture of the L5 system along with the details of how application level information can be efficiently processed in the switch hardware. We cover two specific application examples that we believe are ideal candidates for content-based switching: one is routing HTTP sessions based on uniform resource locators (URL) and the other is session-aware dispatching of secure socket layer (SSL) connections.

Routing driven, metal programmable integrated circuit architecture with multiple types of core cells

Abstract: A user customizable integrated circuit architecture having separate regions for different types of core cells. In an embodiment of the present invention, all asynchronous core cells are placed in a first region and all synchronous core cells are placed in a second region thus allowing clock circuitry to be shared and clock traces to be efficiently routed. Clock buffers may also be placed in the second region. In a second embodiment, high-drive buffers are placed in the second region to enable efficient routing of high-drive power traces to the synchronous cells. Each region also may include metal programmable core cells that may be customized by the user for each design.

Predictable routing

Abstract: Predictable routing is the concept of using prespecified patterns to route a net. By doing this, we allow an more accurate prediction mechanism for metrics such as congestion and wirelength earlier in the design flow. Additionally, we can better plan the routes, insert buffers and perform wire sizing earlier. With comparable routing quality, we show that we can predictably route up to 80% of a selected subset of nets. Also, we introduce methods for finding a group of nets which can be predictably routed.

A path decomposition approach for computing blocking probabilities in wavelength-routing networks

Abstract: We study a class of circuit-switched wavelength-routing networks with fixed or alternate routing and with random wavelength allocation. We present an iterative path decomposition algorithm to evaluate accurately and efficiently the blocking performance of such networks with and without wavelength converters. Our iterative algorithm analyzes the original network by decomposing it into single-path subsystems. These subsystems are analyzed in isolation, and the individual results are appropriately combined to obtain a solution for the overall network. To analyze individual subsystems, we first construct an exact Markov process that captures the behavior of a path in terms of wavelength use. We also obtain an approximate Markov process which has a closed-form solution that can be computed efficiently for short paths. We then develop an iterative algorithm to analyze approximately arbitrarily long paths. The path decomposition approach naturally captures the correlation of both link loads and link blocking events. Our algorithm represents a simple and computationally efficient solution to the difficult problem of computing call-blocking probabilities in wavelength-routing networks. We also demonstrate how our analytical techniques can be applied to gain insight into the problem of converter placement in wavelength-routing networks.

Generating highly-routable sparse crossbars for PLDs

Abstract: A method for evaluating and constructing sparse crossbars which are both area efficient and highly routable is presented. The evaluation method uses a network flow algorithm to accurately compute the percentage of random test vectors that can be routed. The construction method attempts to maximize the spread of the switch locations, such that any given subset of input wires can connect to as many output wires as possible. Based on Hall's Theorem, we argue that this increases the likelihood of routing.The hardest test vectors to route are those which attempt to use all of the crossbar outputs. Results in this paper show that area-efficient sparse crossbars can be constructed by providing more outputs than required and a sufficient number of switches. In a few specific case studies, it is shown that sparse crossbars with about 90% fewer switches than a full crossbar can be constructed, and these crossbars are capable of routing over 95% of randomly chosen routing vectors. In one case, a new switch matrix which can replace the one in the Altera FLEX8000 family is shown. This new switch matrix uses approximately 14% more transistors, yet can increase the routability of the most difficult test vectors from 1% to over 96%.

Approximation Algorithms for Disjoint Paths and Related Routing and Packing Problems

Abstract: Given a network and a set of connection requests on it, we consider the maximum edge-disjoint paths and related generalizations and routing problems that arise in assigning paths for these requests. We present improved approximation algorithms and/or integrality gaps for all problems considered; the central theme of this work is the underlying multicommodity flow relaxation. Applications of these techniques to approximating families of packing integer programs are also presented.