Showing papers on "Link-state routing protocol published in 1993"

RSVP: a new resource ReSerVation Protocol

Abstract: A resource reservation protocol (RSVP), a flexible and scalable receiver-oriented simplex protocol, is described. RSVP provides receiver-initiated reservations to accommodate heterogeneity among receivers as well as dynamic membership changes; separates the filters from the reservation, thus allowing channel changing behavior; supports a dynamic and robust multipoint-to-multipoint communication model by taking a soft-state approach in maintaining resource reservations; and decouples the reservation and routing functions. A simple network configuration with five hosts connected by seven point-to-point links and three switches is presented to illustrate how RSVP works. Related work and unresolved issues are discussed. >

A survey of wormhole routing techniques in direct networks

Abstract: Several research contributions and commercial ventures related to wormhole routing, a switching technique used in direct networks, are discussed. The properties of direct networks are reviewed, and the operation and characteristics of wormhole routing are discussed in detail. By its nature, wormhole routing is particularly susceptible to deadlock situations, in which two or more packets may block one another indefinitely. Several approaches to deadlock-free. routing, along with a technique that allows multiple virtual channels to share the same physical channel, are described. In addition, several open issues related to wormhole routing are discussed. >

Packet Routing in Dynamically Changing Networks: A Reinforcement Learning Approach

Abstract: This paper describes the Q-routing algorithm for packet routing, in which a reinforcement learning module is embedded into each node of a switching network. Only local communication is used by each node to keep accurate statistics on which routing decisions lead to minimal delivery times. In simple experiments involving a 36-node, irregularly connected network, Q-routing proves superior to a nonadaptive algorithm based on precomputed shortest paths and is able to route efficiently even when critical aspects of the simulation, such as the network load, are allowed to vary dynamically. The paper concludes with a discussion of the tradeoff between discovering shortcuts and maintaining stable policies.

Cyclic transfer algorithms for multivehicle routing and scheduling problems

Abstract: This paper investigates the application of a new class of neighborhood search algorithms—cyclic transfers—to multivehicle routing and scheduling problems. These algorithms exploit the two-faceted decision structure inherent to this problem class: First, assigning demands to vehicles and, second, routing each vehicle through its assigned demand stops. We describe the application of cyclic transfers to vehicle routing and scheduling problems. Then we determine the worst-case performance of these algorithms for several classes of vehicle routing and scheduling problems. Next, we develop computationally efficient methods for finding negative cost cyclic transfers. Finally, we present computational results for three diverse vehicle routing and scheduling problems, which collectively incorporate a variety of constraint and objective function structures. Our results show that cyclic transfer methods are either comparable to or better than the best published heuristic algorithms for several complex and important ...

How bad is naive multicast routing

Abstract: In previous approaches to routing multicast connections in networks, the emphasis has been on the source transmitting to a fixed set of destinations (the multicast group). There are some applications where destinations will join and leave the multicast group. Under these conditions, computing an 'optimal' spanning tree after each modification may not be the best way to proceed. An alternative is to make modest alterations to an existing spanning tree to derive a new one. An extreme, though nonoptimal, variation of this is to use minimal cost source to destination routing for each destination, effectively ignoring the existing multicast tree. The authors examine just how nonoptimal these trees are in random general topology networks and conclude that they are worse by only a small factor. The factor is reduced still further if a hierarchy is imposed on the random network to give a more realistic model. >

Neural networks for shortest path computation and routing in computer networks

Abstract: The application of neural networks to the optimum routing problem in packet-switched computer networks, where the goal is to minimize the network-wide average time delay, is addressed. Under appropriate assumptions, the optimum routing algorithm relies heavily on shortest path computations that have to be carried out in real time. For this purpose an efficient neural network shortest path algorithm that is an improved version of previously suggested Hopfield models is proposed. The general principles involved in the design of the proposed neural network are discussed in detail. Its computational power is demonstrated through computer simulations. One of the main features of the proposed model is that it will enable the routing algorithm to be implemented in real time and also to be adaptive to changes in link costs and network topology. >

A Clustering-Based Optimization Algorithm in Zero-Skew Routings

Abstract: A zero-skew routing algorithm with clustering and improvement methods is proposed. This algorithm generates a zero-skew routing in O(n log n) time for n pins, and it is proven that the order of the total wire length is best possible. Our algorithm achieves 20% reduction of the total wire length on benchmark data compared with the best known algorithm.

Computing approximate blocking probabilities for large loss networks with state-dependent routing

Abstract: A reduced load approximation (also referred to as an Erlang fixed point approximation) for estimating point-to-point blocking probabilities in loss networks (e.g., circuit switched networks) with state-dependent routing is considered. In this approximation scheme, the idle capacity distribution for each link in the network is approximated, assuming that these distributions are independent from link to link. This leads to a set of nonlinear fixed-point equations which can be solved by repeated substitutions. The accuracy and the computational requirements of the approximation procedure for a particular routing scheme, namely least loaded routing, is examined. Numerical results for six-node and 36-node asymmetric networks are given. A novel reduced load approximation for multirate networks with state-dependent routing is also presented. >

System for extending network resources to remote networks

Abstract: A system for interconnecting networks transparently extends the multiprotocol routing functionality of a router across a communication link to a remote LAN, while requiring a device on the remote LAN which operates independent of the higher layer protocol suites. A boundary router, having a local routing interface coupled to the first network, and a remote routing interface coupled to the communication link, provides the higher level protocol suite services for routing frames of data to terminals in the first and second networks. A routing adapter extends the remote routing interface of the boundary router transparently across the communication link to the second network.

A comparison of adaptive wormhole routing algorithms

Abstract: Improvement of message latency and network utilization in torus interconnection networks by increasing adaptivity in wormhole routing algorithms is studied. A recently proposed partially adaptive algorithm and four new fully-adaptive routing algorithms are compared with the well-known e-cube algorithm for uniform, hotspot, and local traffic patterns. Our simulations indicate that the partially adaptive north-last algorithm, which causes unbalanced traffic in the network, performs worse than the nonadaptive e-cube routing algorithm for all three traffic patterns. Another result of our study is that the performance does not necessarily improve with full-adaptivity. In particular, a commonly discussed fully-adaptive routing algorithm, which uses 2n virtual channels per physical channel of a k-ary n-cube, performs worse than e-cube for uniform and hotspot traffic patterns. The other three fully-adaptive algorithms, which give priority to messages based on distances traveled, perform much better than the e-cube and partially-adaptive algorithms for all three traffic patterns. One of the conclusions of this study is that adaptivity, full or partial, is not necessarily a benefit in wormhole routing.

Minimum crosstalk channel routing

Abstract: As technology advances, interconnection wires are placed in closer proximity and circuits operate at higher frequencies. Consequently, reduction of crosstalk between interconnection wires becomes an important consideration in VLSI design. In this paper, we study the gridded channel routing problem with the objective of satisfying crosstalk constraints for the nets. We proposed a new approach to the problem which utilizes existing channel routing algorithms and improves upon the routing results by permuting the routing tracks. The permutation problem is proven to be NP-complete. A novel mixed ILP formulation and effective procedures for reducing the number of variables and constraints in the mixed ILP formulation are then presented. The new algorithm is tested on three large benchmark circuits as well as many randomly generated circuits. The experimental results are very promising.

Fault-tolerant wormhole routing in meshes

Abstract: It is shown how to modify the routing algorithms produced by the turn model to encompass dynamic faults The authors describe how to modify the negative-first routing algorithm, which the turn model produces for n-dimensional meshes without virtual channels, to make it one-fault tolerant Simulations of the one-fault-tolerant routing algorithms in a two-dimensional mesh indicate that misrouting increases communication latencies significantly at high throughputs The conclusion is that misrouting should be used only for increasing the degree of fault tolerance, never for just increasing adaptiveness Finally, the authors describe how to modify the negative-first routing algorithm to make it (n-1)-fault tolerant for n-dimensional meshes

A Distributed Reinforcement Learning Scheme for Network Routing

Abstract: In this paper we describe a self-adjusting algorithm for packet routing, in which a reinforcement learning module is embedded into each node of a switching network. Only local communication is used to keep accurate statistics at each node on which routing policies lead to minimal delivery times. In simple experiments involving a 36-node, irregularly connected network, this learning approach proves superior to a nonadaptive algorithm based on precomputed shortest paths.

Adaptive routing protocols for hypercube interconnection networks

Abstract: A taxonomy for characterizing adaptive routing protocols for hypercube interconnection networks (HINs) is presented. The taxonomy is based on classes of routing decisions common to any HIN. This taxonomy is used to discuss existing and proposed protocols. Rather than an exhaustive enumeration of related research, the protocols selected for discussion are intended to be representative of the classes defined by the taxonomy. These protocols are candidates for use in massively parallel architectures configured with HINs. To provide some insight into their behavior in very large HINs, results of simulation studies of representative protocols are presented. >

Methods and apparatus for routing packets in packet transmission networks

Abstract: A packet communications system provides for point-to-point packet routing and broadcast packet routing to limited subsets of nodes in the network, using a routing field in the packet header which is processed according to two different protocols. A third protocol is provided in which a packet can be broadcast to the limited subset even when launched from a node which is not a member of the subset. The routing field includes a first portion which contains the route labels necessary to deliver the packet to the broadcast subset. A second portion of the routing field contains the broadcast subset identifier which can then be used to deliver the packet to all of the members of the broadcast subset. Provision is made to backtrack deliver the packet to the last node identified before the broadcast subset if that last node is itself a member of the subset.

Economical payload stream routing in a multiple-ring network

Abstract: The present invention is directed to a system for routing data between rings. A routing symbol is provided, and as it crosses a bridge, the local target address of the bridge is dropped, and the local source address of the bridge node (in the far side ring) is added to the routing symbol. Fields are shifted in the routing symbol so that the value that was in a hop field becomes the local target address in the new ring. Because the routing symbol that arrives at the ultimate target has been transformed into a source node list, the return path is available to the target.

Asynchronous transfer mode communication system

Abstract: An ATM communication system capable of minimizing the delay period and achieving high throughput without requiring setting of the corresponding virtual connection (VC) table and routing. The communication system includes a vacant virtual connection table indicating unused VC. The VC is retrieved in response to a transmission demand and set in an ATM cell as a virtual connection ID (VCI). Then, the cell is transmitted with added address information identifying the destination. An ATM switch and a routing controller determine routing from a transmitting terminal to a receiving terminal. The determined routing is stored in a routing table in the routing controller. Then, through the determined routing, data is transferred from the transmitting terminal to the receiving terminal.

Algorithms for the vehicle routing problems with time deadlines

Abstract: SYNOPTIC ABSTRACTThe vehicle routing problem with time deadlines (VRPTD) is an extension of the classical vehicle routing problem (VRP) with constraints on the latest allowable time (deadline) for servicing each customer. The objective is to minimize the number of vehicles and the distance travelled without exceeding the capacity of the vehicles or violating the customer deadlines. VRPTD belongs to the class of NP-complete problems. As the computational time taken to solve such problems using exact methods is prohibitive, heuristic methods are used instead to obtain near optimal solutions for large-size problems. We develop three heuristics to solve the VRPTD: deadline sweep, push-forward insertion and genetic sectoring. The solutions obtained by these heuristics are improved using a local post-optimization procedure. Computational analysis of the three heuristics are reported on 25 problems consisting of 200 customers each with different geographical and temporal characteristics.

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. 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 show how to use the model to prove that a given adaptive routing algorithm is deadlock-free. Finally, we use the method to de? velop new, efficient adaptive routing algorithms for 2D meshes and hypercubes.

Routing in frequency-hop packet radio networks with partial-band jamming

Abstract: Research in adaptive, decentralized routing for frequency-hop packet radio networks with mobile partial-band jamming. A routing technique called least-resistance routing (LRR) is developed, and various versions of this routing method are examined. LRR uses a quantitative assessment of the interference environment experienced by a radio's receiver to determine a resistance value for that radio. Two components for the interference environment are considered: transmissions from other radios and partial-band jamming. The resistances for each of the radios in a particular path are combined to form the path resistance, and packets are forwarded on the path with the smallest resistance. Comparisons are made between different versions of LRR and between LRR and previously developed adaptive routing techniques. It is found that LRR is an effective way for dealing with mobile jamming in a frequency-hop packet radio network. Significant increases in throughput and end-to-end probability of success are obtained with LRR. >

A direct combination of the Prim and Dijkstra constructions for improved performance-driven global routing

Abstract: Motivated by analysis of distributed RC delay in routing trees, a new tree construction is proposed for performance-driven global routing which directly trades off between Prim's minimum spanning tree algorithm and Dijkstra's shortest path tree algorithm. This direct combination of two objective functions and their corresponding optimal algorithms contrasts with the more indirect 'shallow-light' methods. The authors' method achieves routing trees which satisfy a given routing tree radius bound while using less wire than previous methods. Detailed simulations show that these wirelength savings translate into significantly improved delay over standard MST routing in both IC and multichip module (MCM) interconnect technologies. >

Adaptive Deadlock-Free Routing in Multicomputers Using Only One Extra Virtual Channel

Abstract: We present three protocols defin ing the relationship between messages and the chan nel resources requested: request-then-hold, requestthen wait, and request-then-relinquish. Based on the three protocols, we develop an adaptive deadlockfree routing algorithm called the SP routing. The SP routing uses shortest paths and is fully-adaptive, so messages can be routed via any of the shortest paths from the source to the destination. Since it is a minimal or shortest routing, the SP routing guar antees the freedom of livelocks. The SP routing is not limited to a specific network topology. The main requirement for an applicable network topology is that there exists a deterministic, minimal, deadlock-free routing algorithm. Most ex isting network topologies are equipped with such an algorithm. In this paper, we present an adaptive deadlock-free routing agorithm for n-dimensional meshes by using the SP routing. The hardware re quired by the SP routing uses only one extra virtual channel as compared to the deterministic routing.

Fast deflection routing for packets and worms

Abstract: We consider deflection routing on the n x n mesh and torus. In deflection routing a message cannot be buffered, and is therefore always moving until it reaches its destination. In addition, routing choices have to be made locally. We give a nearly optimal deterministic algorithm for the permutation routing problem for packets, the first such result for deflection routing. We extend the deterministic algorithm to the case when the messages are worms; a contiguous physical stream of bits that must follow the head of the message uninterrupted through the network. We then give an optimal randomized algorithm for permutation routing for worms of any length up to n.

Optically processed self-routing, synchronization, and contention resolution for 1-D and 2-D photonic switching architectures

Abstract: The use of optical processing to perform switch routing functions permits real-time routing of packets at high speed. The architecture of a 2*2 photonic packet switching node using optically processed fixed-directory routing, contention resolution using deflection routing, and synchronization is presented. Simplified optically processed self-routing procedures are found for banyan and lattice networks. Although lattice networks require a larger number of switching elements than banyan networks, they have a simpler interconnection field, and unlike banyan networks, the self-routing rule for lattices can avoid any internal blocking. The layout of a self-routing 2-D lattice, using 2*2 switches and a smart pixel, is described. Based on a first-arrival self-routing rule, an additional processing logic is required to perform routing. >

Routing multipoint connections using virtual paths in an ATM network

Abstract: The point-to-multipoint routing problem is studied for an asynchronous transfer mode (ATM) network that uses virtual paths (VPs). ATM networks with asymmetric and symmetric VPs are considered, and the performance factors studied are bandwidth and establishment and switching costs. A VP with intermediate exit, where a node that performs VP switching can copy the switched packets for the local destination, is proposed and studied. Mathematical formulations of multicast routing problems are presented, and heuristics for finding a low cost multicast routing tree, based on the transshipment simplex algorithm, are developed. >

An analytical model for adaptive routing networks

Abstract: Real-time network routing (RTNR) is a new adaptive routing method. With RTNR, switches have a simple way of exchanging link status bit map information, thereby determining the availability and load conditions of the direct and all two-link paths to the destination. Link busy-idle status is exchanged between the network nodes using a bit map data exchange through the common channel signaling (CCS) network, and calls are set up where there is the most available capacity in the network. To date the analysis of RTNR networks has been limited to simulation models. The present authors develop an analytical model for the AT&T network under RTNR, which is shown to provide good agreement with simulation models. The analytical model for RTNR networks uses an Erlang fixed point method to solve the nonlinear equations describing dynamical network behavior. The equations include the link state probability, network flows, link arrival rates, adaptive trunk reservation level, and adaptive path selection depth. The link state model provides the aggregate link state probabilities through solution of the birth-death equations, and models the adaptive nature of trunk reservation. The network flow model provides a method to calculate the traffic flow using the least busy concept employed in RTNR, and also models the adaptive nature of the path selection depth. The analytical model addresses asymmetrical networks, and computational examples show the differences from the simulation model to be small. The authors also use the analytical model to examine key RTNR parameters over a range of values. >

An Efficient Timing-Driven Global Routing Algorithm

Abstract: In this paper, we propose an efficient timing-driven global routing algorithm. Unlike other conventional global routing techniques, interconnection delays are modeled and included during routing and rerouting process in order to minimize the routing area as well as to satisfy timing constraint. The timing-driven global routing problem is formulated as a multiterminal, multicommodity flow problem with integer flows and additional timing constraint. Two efficient timing-driven Steiner tree approach and one Steiner tree improving approach have been used to create initial routing results and reroute trees respectively. The algorithm has been implemented and the experimental results are quite promising.

Integration of security in network routing protocols

Abstract: There are two sources of threats to secure operation of routing protocols in networks. The first source of threats is subverted routers that legitimately participate in a routing protocol. The second source of threats is intruders which may illegally attempt to interfere in routing protocols by masquerading as routers. In this paper, we first analyse the security requirements of network routing protocols and then discuss the necessary measures which can be adopted to make the operation of these protocols secure.