Showing papers on "Equal-cost multi-path routing published in 1991"

A Tree-Based Packet Routing Table for Berkeley Unix.

Abstract: Packet forwarding for OSI poses strong challenges for routing lookups: the algorithm must be able to efficiently accommodate variable length, and potentially very long addresses. The 4.3 Reno release of Berkeley UNIX† uses a reduced radix tree to make decisions about forwarding packets. This data structure is general enough to encompass protocol to link layer address translation such as the Address Resolution Protocol (ARP), and the End System to Intermediate System Protocol (ES−IS), and should apply to any hierarchical routing scheme, such as source and quality-of-service routing, or choosing between multiple Datakits on a single system. The system uses a message oriented mechanism to communicate between the kernel and user processes to maintain the routing database, inform user processes of spontaneous events such as redirects, routing lookup failures, and suspected timeouts through gateways.

System and method for interconnecting local area networks

Abstract: A transmission system transmits data among interconnected local area networks using a bridge coupled between local area networks which senses whether the data originating node transmitted the data using transparent routing or source routing. The bridges provide interconnection at the MAC-layer and based upon information contained in the MAC-layer header, automatically perform either transparent routing or source routing, depending upon the type of routing used by the data originating node. In addition, the bridge provides source routing over multiple wide area channels to those nodes which use source routing.

A framework for adaptive routing in multicomputer networks

Abstract: Message-passing concurrent computers, also known as multicomputers, such as the Caltech Cosmic Cube [47] and its commercial descendents, consist of many computing nodes that interact with each other by sending and receiving messages over communication channels between the nodes. The communication networks of the second-generation machines, such as the Symult Series 2010 and the Intel iPSC2 [2], employ an oblivious wormhole-routing technique that guarantees deadlock freedom. The network performance of this highly evolved oblivious technique has reached a limit of being capable of delivering, under random traffic, a stable maximum sustained throughput of ~~45 to 50% of the limit set by the network bisection bandwidth, while maintaining acceptable network latency. This thesis examines the possibility of performing adaptive routing as an approach to further improving upon the performance and reliability of these networks. In an adaptive multipath routing scheme, message trajectories are no longer deterministic, but are continuously perturbed by local message loading. Message packets will tend to follow their shortest-distance routes to destinations in normal traffic loading, but can be detoured to longer but less-loaded routes as local congestion occurs. A simple adaptive cut-through packet-switching framework is described, and a number of fundamental issues concerning the theoretical feasibility of the adaptive approach are studied. Freedom of communication deadlock is achieved by following a coherent channel protocol and by applying voluntary misrouting as needed. Packet deliveries are assured by resolving channel-access conflicts according to a priority assignment. Fairness of network access is assured either by sending round-trip packets or by having each node follow a local injection-synchronization protocol. The performance behavior of the proposed adaptive cut-through framework is studied with stochastic modeling and analysis, as well as through extensive simulation experiments for the 2D and 3D rectilinear networks. Theoretical bounds on various average network-performance metrics are derived for these rectilinear networks. These bounds provide a standard frame of reference for interpreting the performance results. In addition to the potential gain in network performance, the adaptive approach offers the potential for exploiting the inherent path redundancy found in richly connected networks in order to perform fault-tolerant routing. Two convexity-related notions are introduced to characterize the conditions under which our adaptive routing formulation is adequate to provide fault-tolerant routing, with minimal change in routing hardware, The effectiveness of these notions is studied through extensive simulations, The 2D octagonal-mesh network is suggested; this displays excellent fault-tolerant potential under the adaptive routing framework. Both performance and reliability behaviors of the octagonal mesh are studied in detail. A number of

Neural network implementation of the shortest path algorithm for traffic routing in communication networks

Abstract: A neural network computation algorithm is introduced to solve for the optimal traffic routing in a general N-node communication network. The algorithm chooses multilink paths for node-to-node traffic which minimize a certain cost function. Unlike the algorithm introduced earlier in this area, knowledge of the number of links between each origin-destination pair is not required by the algorithm, therefore it can be applied to variable-length path routing problems. The neural network structure for implementing the algorithm is a modified form of the one used by the traveling salesman algorithm. Computer simulation in a nine- and sixteen-node grid network showed that the algorithm performs extremely well in single and multiple paths. >

Message-routing apparatus

Abstract: Message-routing apparatus is known for routing messages between a plurality of communications networks. Typically, the known apparatus comprises a respective network interface card for each communications network and a shared, processor-based, routing manager with which the cards communicate through a backplane bus system. In order to overcome the bandwidth limitations of such known apparatus, the present invention provides a local routing manager on each card and high-speed, point-to-point, links interconnecting the local routing managers in a closed loop. Each local routing manager recognizes whether a message passed to it is for outward transmission over the associated network; if this is not the case, the message is passed to the local routing manager of the next card. Any messages which the local routing managers are unable to route, are diverted to a shared routing manager.

Novel routing schemes for IC layout part I: Two-layer channel routing

Abstract: We present new channel routing algorithms and theory that consider the characteristic of net crossings. ‘llte routing strategy is based on parallel bubble sorting and river routing tectilques. A fiction named POTENTfAL, cart be evaluated to indicate the required channel height for a given channel witbout actually carrying out the routing steps. Non-Manhattan wires as wefl as overlapping wires are introduced. Preliminary results show that a class of channel muting problems cart be muted in height less than the Manhattan density.

Deadlock-free multicast wormhole routing in multicomputer networks

Abstract: Efficient routing of messages is the key to the performance of multicomputers. Multicast communication refers to the delivery of the same message from a source node to an arbitrary number of destination nodes. Wormhole routing is the most promising switching technique used in new generation multicomputers. In this paper, we present multicast wormhole routing methods for multicomputers adopting 2D-mesh and hypercube topologies. The dual-path routing algorithm requires less system resource, while the multipath routing algorithm creates less traffic. More import antly, both routing algorithms are deadlock-free, which is essential to wormhole networks.

Routing apparatus and method for high-speed mesh connected local area network

Abstract: A packet routing apparatus allows numerous packets to be routed simultaneously through a mesh connected network. The network consists of a number of interconnected switches which are coupled, in turn, to the hosts that are members of the local network. The switches are nonblocking switches that are coupled to each other and to the hosts by a multiplicity of point to point links. Each switch has a routing mechanism for automatically routing received packets toward their specified destinations. For each received packet the router generates a routing mask representing the output links that may be used to route the packet towards its destination. The routing mask includes a broadcast bit. If the broadcast bit is ON, the packet must be simultaneously routed to all of the output links specified by the routing mask. If the broadcast bit is OFF, the packet may be routed on any single one of the links specified by the routing mask. To ensure that every packet makes progress towards its destination, packets are processed in the order of their arrival by placing the corresponding routing masks in a queue. Periodically, the set of available output links is compared with all of the routing masks. Using a first come, first considered routing discipline, the first routing mask in the queue to match the available output lines is selected. A routing selection is then generated for the corresponding packet and the selected routing mask is removed from the queue.

Topological routing in SURF: Generating a rubber-band sketch

Abstract: A multi-layer topological router for generating rubberband sketches is described. The router uses hierarchical togdown partitioning to perform global routing for all nets simultaneously. I t combines this with successive refinement to help correct mistakes made before more detailed local information is discovered. Layer assignment is performed during the partitioning process to generate routing that has fewer vias and is not restricted to one-layer one-direction. The local router uses a region connectivity graph to generate shortest-path rubber-band routing.

Deadlock-free adaptive routing algorithms for multicomputers: evaluation of a new algorithm

Abstract: A new theory for the design of deadlock-free adaptive routing algorithms for wormhole and store-and-forward routing as well as two design methodologies have been proposed previously. In this paper, a new adaptive routing algorithm, obtained from the application of the former theory to the binary n-cube, is evaluated under different load conditions and compared with other algorithms. The results show that the new design methodology supplies faster routing algorithms, at least for those networks with a high connectivity. >

A comparison between two routing protocols: OSPF and IS-IS

Abstract: A comparison is made of the open shortest path first (OSPF) and intermediate system-to-intermediate system (IS-IS) routing protocols in terms of their ability to route internet protocol (IP) traffic. Common characteristics of the two protocols are briefly indicated. The differences between the two are explored with respect to packet encoding, area partitions, level 2 partitions, injection of level 2 information, authentication, designated router election, link state packet propagation, synchronized parameter setting, and neighbor initialization. >

A general greedy channel routing algorithm

Abstract: A general approach for the channel routing problem is presented as a framework for a class of heuristic routing algorithms. The algorithm is shown to possess a backtracking capability that increases the chance of completing the routing with a minimum number of tracks. Since the concepts described are general, they can be applied to other channel problems, such as switchbox routing, three-layer routing, and multilayer routing, or even to the overlap model, with only a few modifications. It is shown that track-oriented greedy algorithms can be modified to solve other channel routing problems. As examples, the algorithm is modified to solve the Manhattan switch-box problem and channel routing problems in the overlap and knock-knee models. Preliminary results show that the modified algorithms have good performance and show strong potential to outperform existing algorithms. Applying the algorithm MCRP-ROUT to the benchmark Deutsch's difficult problem and Burstein's difficult problem, routing solutions of 19 tracks and six tracks, respectively, were obtained. >

Fully-adaptive minimal deadlock-free packet routing in hypercubes, meshes, and other networks

Abstract: This paper deals with the problem of packet-switched routing in parallel machines. Several new routing algorithms for different interconnection networks are presented. While the new techniques apply to a wide variety of networks, routing algorithms will be shown for the bypercube, the 2-dinleusional mesh, and the shuffleexchange. The techniques presented for hypercubes and meshes are fully-adaptive and minimal. A similar technique can be devised for tori. A fully-adaptive and millimal routing is one in which all possible minimal paths bet,ween a source and a destination are of potential use at the time a message is injected into the network. Minimal paths followed by messages ultimately depend on the local congestion encountered in each node of the network. In the shuffle-exchange network, the routing scheme also exhibits adaptivity but paths could be up to 3 log N long for an N node machine. The shuflleexchange algorithm is the first adaptive and deadlockfree method that requires a small (and independent of N) number of buffers and queues in the routing nodes for that network. * ESLAI, Escuela Superior Latino Americana de Informitica, CC 3193,(1000) Buenos Aires, Argentina. t Computer Research and Advanced Applications Group, IBM Argentina, Ing. E. Bntti 275, (1300) Buenos Aires, Argentina. + Computer Science Dept., IBh’1 Almadeu Research Center, San

Channel routing by sorting

Abstract: A novel approach for the channel routing problem based on sorting is described. A router based on the bubble-sort for routing two point nets across a channel is presented. A lower and an upper bound on the channel width and an upperbound on the number of vias are given. The router is extended for handling multiterminal nets and single-sided connections. Results for multilayer channel routing are presented. The high-speed and predictable performance of these channel routing algorithms makes them valuable in assessing the difficulty of routing a particular configuration of logic blocks. This makes then suitable for use when calculating a cost metric in an iterative placement algorithm. >

Constant queue routing on a mesh

Abstract: Packet routing is an important problem in parallel computation since a single step of inter-processor communication can be thought of as a packet routing task. In this paper we present an optimal algorithm for packet routing on a mesh-connected computer.

Fully-adaptive routing: packet switching performance and wormhole algorithms

Abstract: In thts paper, a strnulatton study on the performance of some new algorithms for deadlock- and lwelock-free adaptive routing is reported. Packetswztchcd fully -adaptive minzmal routing on the mesh and the hypercube as ezplored for dt~erent tn~ection models: stattc and dynamic. The algorithms stmu lated in this paper are the jirst known to be !ivelockand deadlock-free fully -adaptive minimal that requzre a moderate amount of hardware. These techniques need only two central queues per routing node. The performance of these schemes IS measured for dtfferent irafic models: random, complement, transpose, bit-reversal and leveied permutations. Several machine sizes are trted and critical parameters indicating the performance of the routing algorithms are measured such as throughput, maximum and average latency, effective tn~ectaon, and saturation point. In the case of the mesh network, the new method w compared to an obltvzous scheme based on a simtlar routing node model. In the present versaon of thts paper, stm u!atton results are reported for hypercubes up to 16K nodes and for meshes of 11{ nodes. Ftnallyl a fu!iy-adaptwe minzmal worm-hole routing algorathm for the torus network wiil be presented. This technique is dead!ock- and hvelock-free and requuvs only 8 vzrtual channels per physzcal bzdzrectzonal link for zts implementation. Szmu!ations are currently being performed to determme the practical performance of this routing method.

Hierarchical network routing

Abstract: A disadvantage of Link State routing schemes is that exact shortest path calculations require a complete topology, which can overload the capacity of small nodes in a large network. Area routing schemes (when destination names are structured corresponding to the network topology) allow nodes to reduce the size of routing tables, by recording only one entry for an entire region rather than one for each node in the region. A description is presented of a general hierarchical routing scheme that allows all nodes to participate in a distributed routing network, using close to optimal paths, with short routing tables, and a reduction of topology information for minor nodes. >

The effect of model uncertainty on some optimal routing problems

Abstract: The effect of model uncertainties on optimal routing in a system of parallel queues is examined. The uncertainty arises in modeling the service time distribution for the customers (jobs, packets) to be served. For a Poisson arrival process and Bernoulli routing, the optimal mean system delay generally depends on the variance of this distribution. However, as the input traffic load approaches the system capacity the optimal routing assignment and corresponding mean system delay are shown to converge to a variance-invariant point. The implications of these results are examined in the context of gradient-based routing algorithms. An example of a model-independent algorithm using online gradient estimation is also included. >

A new model for over-the-cell channel routing with three layers

Abstract: The authors propose an approach to an over-the-cell channel routing problem using a model that consists of two channels and the routing area over a cell row between them. Three and two layers are available for routing in the channels and the over-the-cell routing area, respectively, The problem is decomposed into two phases: over-the-cell routing and channel routing. The authors formulate the problem in the first phase as that of channel routing with additional constraints. Based on this formulation, they present an efficient over-the-cell routing algorithm. The effectiveness of the approach is demonstrated by experimental results on sea-of-gates array chips. >

Method and circuit arrangement for the acceptance and forwarding of message cells transmitted according to an asynchronous transfer mode by an asynchronous transfer mode switching equipment

Abstract: For receiving and forwarding message cells transmitted according to an asynchronous transfer mode (ATM) by an ATM switching equipment which comprises a multi-stage reversing switching matrix network, each of the message cells has a routing information block having a plurality of routing information corresponding in number of the plurality of switching matrix stages to be traversed located in front thereof within the ATM switching equipment and the routing information just evaluated for the forwarding of a message cell through one of the switching matrix stages is subsequently displaced to the end of the respective routing information block. It is thereby provided that each of the routing information of the routing information block has a separate security information attached thereto and the security information is falsified, together with the displacement of a routing information to the end of the respective routing information block. A message cell is thereby only forwarded via a switching matrix stage when the routing information to be evaluated for that purpose has been recognized as being free of error on the basis of the attached security information.

A minimum interference routing algorithm for a linear lightwave network

Abstract: A routing algorithm for setting up point to point connection is proposed for a linear lightwave network (LLN). The overall problem of routing is decomposed into the subproblems of physical path allocation, checking for violations of some of the special constraints (MISC (mutually independent sources combining) and color clash) of the LLN on the allocated physical path and the allocation of an appropriate channel. It is shown that the problem of finding a physical path that does not violate the MISC constraint of the LLN is NP-complete. >

Flexible, fault-tolerant routing criteria for circuit-switched hypercubes

Abstract: A set of routing criteria is proposed for circuit-switched hypercubes that exploit the flexibility provided by the hypercube. The routing criteria are provably deadlock-free and route messages along shortest paths. The number of shortest paths allowed by the routing criteria is more than one for most source-destination pairs. It is shown that the flexibility provided by the routing criteria can be used to limit the negative effects due to component-failures. The exact number of disrupted source-destination pairs are derived in the presence of a single faulty link or a single faulty node. It is shown that these numbers can be minimized using the relabeling techniques proposed. It is shown that the criteria, if used effectively, lead to a significant improvement in performance over the e-cube routing strategy for non-uniform traffic. >

A routing strategy for MAN interconnection

Abstract: The authors propose a combined routing strategy to overcome the problems connected with applying routing schemes usually adopted in bridged LANs to a LAN-MAN (metropolitan area network) internet. The strategy uses a spanning tree for multicasting within user groups, and shortest paths for point-to-point forwarding. The authors show that the algorithms can scale up efficiently to large network sizes. They also present various enhancements of the basic algorithms, which can substantially improve performance in specific environments. >

Connectivity database overhead for inter-domain policy routing

Abstract: Policy routing protocols incorporate policy related constraints into the route computation and packet forwarding functions for inter-administrative domain (AD) communication. However, this functionally exacerbates the already critical problem of routing information distribution and storage overhead in very large internets (e.g., 100000 ADs). The authors investigate the scalability of the inter-domain policy routing (IDPR) architecture. In particular, they present an informal analysis of connectivity database and update overhead. A model of the IDPR architecture is defined and tested by varying several parameters. The results obtained illustrate the scaling properties of the IDPR architecture and their dependencies upon internet configuration, connectivity among ADs, and number of policies. It is found that, under certain reasonable assumptions, global information for an internet of 5000 transit ADs (and 50000 stub ADs) will occupy on the order of 2.5 MB of storage in the route server. >

Team theory and backpropagation for dynamic routing in communication networks

Abstract: The dynamic routing problem in communication networks is considered. Traffic routing nodes are required to generate routing decisions on the basis of local information, and to compute or adapt their routing strategies online. The first requirement leads to regarding routing nodes as the cooperating decision makers of a team organization. The second requirement calls for a computationally distributed algorithm. This fact and the impossibility of solving, under general conditions, team functional optimization problems suggest that each routing node be assigned a set of multilayer feedforward neural networks able to generate routing decisions. The weights of such neural networks are then adjusted by means of an algorithm based on backpropagation. >

Distributed fault-tolerant routing on hypercubes algorithms and performance study

Abstract: Increasing use of hypercube systems in reliability-critical applications has made fault-tolerant communication algorithms for hypercube important. This paper describes four fault-tolerant routing algorithms for hypercubes subject to link failures, namely any/sub -/nd, sidewalk, lookahead and lookside. The principle of sidewalk and lookahead are similar to two existing approaches. Lookside is an improved version of either of them. Sidewalk, lookahead and lookside guarantee successful routing in a d-cube if the number of link failures is less than d. For higher degree of link failures, the authors measure their performance by probability of successful routing and expected routing distance using two fault distribution models, probability fault model and random fault model. Lookside demonstrates better properties than sidewalk and lookahead in that it has the highest successful routing rate with reasonable routing distance. >