Showing papers on "Dynamic Source Routing published in 1981"

Design and optimization of networks with dynamic routing

Abstract: The growth of electronic switching systems and the high-capacity interoffice signaling network provide an opportunity to extend telephone network routing rules beyond the conventional hierarchy. Network models are described that illustrate the savings inherent in designing networks for dynamic, nonhierarchical routing. An algorithm for engineering such networks is discussed, and the comparative advantages of various path-routing and progressive-routing techniques are illustrated. A particularly simple implementation of dynamic routing called two-link dynamic routing with crankback is discussed and is shown to yield benefits comparable to much more complicated routing schemes. The efficient solution of embedded linear programming (LP) routing problems is an essential ingredient for the practicality of the design algorithm We introduce an efficient heuristic optimization method for solution of the LP routing problems, which greatly improves computational speed with minimal loss of accuracy. We also project computational requirements for a 200-node design problem, which is the estimated size of the intercity Bell System dynamic routing network in the 1990s.

Servicing and real-time control of networks with dynamic routing

Abstract: The design of a network for dynamic routing is made using the forecasted network loads. Load uncertainties arising from errors in the forecast and from daily variations in network load give rise to reserve or idle network capacity not immediately needed by current network demands. The reserve capacity can be reduced by the use of more flexible dynamic routing methods, which allow routing flexibility to help control network flow under load uncertainties. We illustrate techniques for changing network routing patterns in planned and demand servicing to counteract the effects of forecast errors. Included in the benefits are a reduction in both reserve capacity, estimated to be about 5 percent of network first cost, and in trunk rearrangements. We also present call-by-call simulation results for real-time routing enhancements to the basic routing algorithms. The real-time routing algorithms use dynamic trunk reservation techniques, and the simulation results illustrate the improvement in network efficiency and performance under normal daily load variations, network overloads, and network failures.

Advances in Verifiable Fail-Safe Routing Procedures

Abstract: Two new versions of a distributed protocol for establishing and maintaining loop-free routing tables for communication networks with changing topology are presented. The protocols here possess significant advantages over previous versions in terms of complexity of the node algorithm and of the validation procedure, as well as the communication and storage needs. In addition, we present a procedure for establishing new and disrupted calls in a virtual or physical circuit-switched network, and for canceling existing calls, such that each call is loop-free and is established according to the routing tables provided by the protocol.

A Technique for Adaptive Routing in Networks

Abstract: A two-level adaptive routing scheme for packet-switched computer communication networks is proposed and investigated. The first level is quasi-static and based on the global network status. The second level is dynamic with decisions being made at each node in an attempt to obtain the savings in average delay predicted by a multiserver model of the node. Simulations confirm the predicted improvement.

Optimal Routing in Rectilinear Channels

Abstract: Programs for integrated circuit layout typically have two phases: placement and routing. The router should produce as efficient a layout as possible, but of course the quality of the routing depends heavily on the quality of the placement. On the other hand, the placement procedure would like to know how good a routing it can expect without actually routing the wires. This paper presents fast algorithms for optimal routing and for accurately estimating the area cost of such routings without actually laying them out.

A Failsafe Distributed Protocol for Minimum Delay Routing

Abstract: Previous distributed routing protocols in data-communication networks that achieve minimum average delay are extended to take into consideration topological changes in the network.

Notes on Optimal Routing and Flow Control for Communication Networks.

Abstract: : The main purpose of routing and flow control in a communication network is, roughly speaking, to keep delay per message within an acceptable level while minimizing the amount of offered traffic that is rejected by the network due to its inability to handle it. These two objectives are clearly contradictory so a good routing and flow control scheme must strike a balance between the two. It should also take into account a number of other issues such as fairness for all users, the possibility that the network topology can be altered due to unexpected link or node failures, and the fact that the statistics of offered traffic change with time. In these notes we consider some aspects of routing and flow control for long-haul wire data networks in which the communication resource is scarce (as opposed to local networks such as Ethernet where it is not), and where there are no issues of contention resolution due to random access of a broadcast medium (as in some satellite, local, and packet radio networks). We place primary emphasis on optimal procedures since these offer a more sound philosophical basis than heuristic schemes and also provide a yardstick for measuring the effectiveness of other methods.

TWIGY A Topological Algorithm Based Routing System

Abstract: A two-level approach to routing is described, in which a multi-layer printed circuit board routing problem is broken down into a set of single-layer ones. A topological transformation is then applied to accomplish single-layer routing. A solution found for each layer by a search in this new domain is then translated back into physical space by means of a deterministic drawing algorithm. The algorithms are independent of specific technological parameters, affording their use on a variety of board routing grids, pad diameters and wire sizes.

Delay Analysis of Broadcast Routing in Packet-Switching Networks

Abstract: Broadcast addressing is the capability to send a packet from a source node to all other nodes in the network. Store-and-forward, packet-switching networks are not inherently designed to carry broadcast packets, and broadcasting has to be implemented by some sort of routing algorithm. In this paper, the source based forwarding algorithm is considered. With this algorithm, a spanning tree is defined for each node, and broadcast packets are sent along the branches of these trees. Approximation methods are presented to obtain a lower bound and estimates of the mean broadcast time. The accuracy of these methods is evaluated by comparison with simulation.

A distributed minimum hop routing algorithm

Abstract: A two-part distributed algorithm for minimum hop routing in message-switched networks subject to end-to-end average message delay constraints is developed. The first part of the algorithm provides for unconstrained minimum hop routing, while the second corrects this routing to satisfy the delay constraints. Both parts are implemented nodewise via low-order linear programs wherein the information exchange required for each node to carry out its computations involves only adjacent neighbor nodes. The algorithm is illustrated via an example of an 8- node, 14-link network with 7 commodities, and directions for future research to enhance present results are indicated.

Routing traffic in telephone networks

Abstract: Telephone calls arriving at a switching center must be assigned to any one of the outgoing trunks which has idle links. With probability 1-?i the call may be lost due to congestion in subsequent trunks along the route, and with probability ?i the call is successful, and then the links along the route remain busy for an exponential holding time. If the ?i do not depend on the routing policy, then assigning the call to the trunk with largest such ?i minimizes the expected number of lost calls. When ?i does depend upon the policy, a suboptimal policy combining overflow and load sharing is proposed.

Adaptive routing in large communication networks: Probabilistic study

Abstract: A network model is presented and conditions for stochastic stability of the network system are given. For adaptation algorithms which change the routing probabilities slowly (small stepsize), expressions for steady-state variances are derived; usimg these, guidelines for the selection of algorithm parameters are discussed.

Routing in Networks

Abstract: : This report is concerned with routing protocols in networks. The major result is a low bound for any oblivious routing strategy where the route of a packet depends only on the source and destination of the packet. We show that for any oblivious routing protocol for a network of n processors in which the maximum number of processors directly connected to any processor is d, there exists a permutation that requires time (sq. root of n) d (to the 3/2). For specific networks such as an n-cube we give an oblivious routing algorithm whose performance is close to this lower bound. (Author)