Showing papers on "Equal-cost multi-path routing published in 1995"

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. >

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.

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).

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.

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.

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. >

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.

Hierarchical distance-vector multicast routing for the MBone

Abstract: The exponential growth of the Multicast Back-bone (MBone) has resulted in increased routing overhead and processing costs. In this paper we propose a two-level hierarchical routing model as a solution to this problem. This approach involves partitioning the MBone into non-overlapping regions using DVMRP as the inter-region routing protocol; intra-region routing may be accomplished by any of a number of existing multicast protocols. Our design is flexible enough to accommodate additional levels of hierarchy, and protocols other than DVMRP at the higher levels. The unique feature of this approach is the independence of the higher level routing protocol from the subnet addresses, which allows for easy incremental deployment with small changes to existing intra-region protocols.

Method for automatically routing circuits of very large scale integration (VLSI)

Abstract: An automated routing tool for routing interconnections between circuit elements, standard cells and/or cell blocks of cell-based designs which incorporates the best features of both currently known gate array routing techniques with currently known cell-based routing techniques. The invention eliminates the disadvantages of permitting the detailed router to adjust the relative positions of the circuit elements, standard cells and/or cell blocks during the detailed routing process. The method employs a topology manager which iteratively compacts the circuit topology while at the same time optimizing the routing of the interconnections among the circuit elements, standard cells and/or cell blocks of the circuit design. The method employs bin-based global routing, which identifies expandable boundaries and which provides input to a compaction routine which expands or contracts the expandable areas in accordance with the result of the global routing process. The detailed routing step is not performed until after the relative positions of the circuit elements, cells and/or cell blocks have been already fixed.

Method and apparatus for storing and retrieving routing information in a network node

Abstract: Method and apparatus for storing and retrieving routing information in a node of a network, such as an ATM network, are disclosed. A routing table in each node of the network stores the routing information for each active call connection through the node, for example, identified by a virtual path identifier (VPI) and a virtual channel identifier (VCI). The routing table is indexed by a modified header error control (HEC) value, which may be the actual HEC value associated with a given cell, or a value calculated therefrom. Upon receipt of an incoming cell at a network node, the modified HEC value is calculated, to access the appropriate entry of the routing table. The routing table preferably stores a pointer to a memory location, such as a linked list of data structures, storing the actual routing information for each connection. An intermediate node data structure preferably stores the routing information for a particular connection through an intermediate node of the ATM network, while a leaf node data structure preferably stores the routing information for a particular connection associated with a leaf node of the ATM network. If a data structure in the indicated linked list has a VPI/VCI value matching the VPI/VCI value in the received cell header, the routing information for the next link of the call connection is retrieved, and the cell header information is validated.

Minimum-cost bounded-skew clock routing

Abstract: In this paper, we present a new clock routing algorithm which minimizes total wirelength under any given path-length skew bound. The algorithm constructs a bounded-skew tree (BST) in two steps: (i) a bottom-up phase to construct a binary tree of shortest-distance feasible regions which represent the loci of possible placements of clock entry points, and (ii) a top-down phase to determine the exact locations of clock entry points. Experimental results show that our clock routing algorithm, named BST/DME, can produce a set of routing solutions with skew and wirelength trade-off.

Communications network and method which implement diversified routing

Abstract: A communications network (20) includes any number of moving switching nodes (30) and a route-determining node (28). The route-determining node (28) performs an off-line procedure (58) to define a-priori routing for the entire network. This procedure (58) is performed repetitively to track switching node (30) movement and to define routing for numerous epochs included in a planning period. The procedure (58) includes a process (86) for determining all shortest path routes between all possible origination and destination switching nodes (30). Another process (84) matches predicted call traffic for a subject epoch with the shortest path routes. Another process (88) generates routing code tables (54) in response to the predicted call traffic matched to shortest path routes. This process (88) assigns logical routing IDs (52) to physically distinct, shortest path routes in proportion to the predicted call traffic allocated to the distinct routes.

Link-state routing

Abstract: ƒ Same assumptions/goals, but different idea than DV: ƒ Tell all routers the topology and have each compute best paths ƒ Two phases: 1. Topology dissemination (flooding)-New News travels fast.-Old News should eventually be forgotten 2. Shortest-path calculation (Dijkstra's algorithm)-nlogn

Distance-vector routing

Abstract: Your program must start up and read a configuration file, the configuration file will provide you with the IP addresses of your directly connected neighbors, and the cost to reach those neighbors. Your program must connect to the IP addresses specified in the configuration file. Note that to bootstrap the network you are going to need to have your program retry connections that fail. Your program must also accept incoming IP connections, from neighbors, or from my master control client, which may inform you of a link cost change, or may ask you to deliver a message to a particular IP address. You can write your program in the language of your choice, however the program must run on Linux in the Olin 202 lab.

A theory of deadlock-free adaptive multicast routing in wormhole networks

Abstract: A theory for the design of deadlock-free adaptive routing algorithms for wormhole networks, proposed by the author (1991, 1993), supplies sufficient conditions for an adaptive routing algorithm to be deadlock-free, even when there are cyclic dependencies between channels. Also, two design methodologies were proposed. Multicast communication refers to the delivery of the same message from one source node to an arbitrary number of destination nodes. A tree-like routing scheme is not suitable for hardware-supported multicast in wormhole networks because it produces many headers for each message, drastically increasing the probability of a message being blocked. A path-based multicast routing model was proposed by Lin and Ni (1991) for multicomputers with 2D-mesh and hypercube topologies. In this model, messages are not replicated at intermediate nodes. This paper develops the theoretical background for the design of deadlock-free adaptive multicast routing algorithms. This theory is valid for wormhole networks using the path-based routing model. It is also valid when messages with a single destination and multiple destinations are mixed together. The new channel dependencies produced by messages with several destinations are studied. Also, two theorems are proposed, developing conditions to verify that an adaptive multicast routing algorithm is deadlock-free, even when there are cyclic dependencies between channels. As an example, the multicast routing algorithms of Lin and Ni are extended, so that they can take advantage of the alternative paths offered by the network. >

System for customer configuration of call routing in a telecommunications network

Abstract: In a telecommunications network operable for routing calls such as 800 calls, to a plurality of customer destinations, a system allows the customer to configure the routing of calls by entering selected call routing criteria such as a call-routing map associated with a time frame for implementation thereof included as part of an overall routing plan. The routing map includes the desired allocation of calls placed from a customer defined origination region to selected ones of the customer's call receiving destinations. Using the customer supplied criteria, the system then composes a set of call-handling statements, also called time features, which the network then compiles into an executable routing scheme for translating the dialed number into the physical number associated with the selected customer destination.

Scalable multiple level tab oriented interconnect architecture

Abstract: An improved field programmable gate array (FPGA) is provided which includes tab network connectors for interfacing groups of configurable function generators with lower levels of interconnect and for interfacing lower levels of interconnect with higher levels of interconnect. Furthermore, an innovative cluster architecture is utilized which provides fine granularity without a significant increase in configurable function generators. The tab connector network can also be used to route a lower level routing line to a higher level routing line. This is particularly desirable in order to meet the needs for driving a signal along longer routing lines without requiring all signal drivers be sufficiently large to drive a signal along the longest routing line. The connector networks described enable a flexible routing scheme to be implemented in which the routing lines at each level are divided into sets. In addition, the innovative routing hierarchy consisting of the routing lines, block connector tab networks and turn matrices, permits an innovative, space saving floor plan to be utilized that is scalable.

Packet routing system and method with quasi-real-time control

Abstract: In a system that includes a constellation of satellite communication nodes, information packets are routed through the constellation using routing tables stored in each communication node. When a packet is received at a node, the packet's destination and routing table ID are read. One of several routing tables are selected using a mapping table. Each of the several routing tables has a different routing instruction set. The packet is routed away from the node using the selected routing table. When system traffic is heavy, or some of the communication links are overloaded or have failed, routing table control bits are sent to the nodes updating the mapping table. Packets are subsequently routed using different sets of routing tables, such as ones having greater hop counts.

A packet routing protocol for arbitrary networks

Abstract: In this paper, we introduce an on-line protocol which routes any set of packets along shortest paths through an arbitrary N-node network in O(congestion+diameter+log N) rounds, with high probability. This time bound is optimal up to the additive log N, and it was previously only reached for bounded-degree levelled networks.

Computing approximate blocking probabilities for a class of all-optical networks

Abstract: Studies a class of all-optical networks using wavelength division multiplexing and wavelength routing in which a connection between a pair of nodes in the network is assigned a path and a wavelength on that path. Moreover, on the links of that path no other connection can share the assigned wavelength. Using a generalized reduced load approximation scheme the authors calculate the blocking probabilities for the optical network model for two routing schemes: fixed routing and least loaded routing.

Routing in a three-dimensional chip

Abstract: As the very large scale integration (VLSI) technology approaches its fundamental scaling limit at about 0.2 /spl mu/m, it is reasonable to consider three-dimensional (3-D) integration to enhance packing density and speed performance. With additional functional units packed into one chip in a 3-D space, computer-aided design (CAD) tools are demanded to ease the complicated design work. This paper presents a 100% completion achievable routing methodology. The routing methodology is based on the two-dimensional (2D) channel routing methodology; thus, it is called a 3-D channel routing methodology. With the routing methodology, a 3-D routing problem is decomposed into two 2D routing subproblems: intra-layer routing that interconnects terminals on the same layer, which can be done by using a 2-D channel router, and inter-layer routing that interconnects terminals on different layers. The inter-layer routing problem is transformed into a 2-D channel routing problem and the transformation is made in some 3-D channels. Detailed discussions are given for the 3-D to 2-D transformation. Optimization of the transformation is shown to be NP-complete. Thus, simulated annealing is used to optimize the transformation. >

Multiobjective Routing Problems

Abstract: Many network routing problems, particularly where the transportation of hazardous materials is involved, are multiobjective in nature; that is, it is desired to optimise not only physical path length but other features as well. Several such problems are defined here and a general framework for multiobjective routing problems is proposed. The notion of “efficient solution” is defined and it is demonstrated, by means of an example, that a problem may have very many solutions which are efficient. Next, potentially useful solution methods for multiobjective routing problems are discussed with emphasis being placed on the use of shortest/k-shortest path techniques. Finally, some directions for possible further research are indicated.

System for adaptively routing data in switching network wherein source node generates routing message identifying one or more routes form switch selects

Abstract: A method for adaptive routing of messages in a computer network. The method provides adaptive source routing by generating at a source node a routing message describing a plurality of allowable paths via which data message can reach a desired destination. The data message and the routing message are sent by the source to a first switch, and the routing message is evaluated by control logic to determine if an available, allowable path exists. If so, the data message and routing message are sent via that path to the destination.

LLR routing in homogeneous VP-based ATM networks

Abstract: In ATM networks, a virtual path (VP) concept has been proposed to simplify traffic control and resource management. As a consequence, cell routing becomes more flexible and significant call setup processing can be reduced when resources are reserved on VP's. In this paper, we study the routing problem in homogeneous VP-based ATM networks in which VP's are used for traffic segregation such that all VC's in a VP have the same traffic characteristics and QOS requirement. Four adaptive routing algorithms based on the least loaded routing (LLR) concept are designed and evaluated. Our simulation results show that network blocking probability can be significantly reduced by LLR routing.