Showing papers on "Dynamic Source Routing published in 1994"

Dynamic Source Routing in Ad Hoc Wireless Networks.

Abstract: An ad hoc network is a collection of wireless mobile hosts forming a temporary network without the aid of any established infrastructure or centralized administration. In such an environment, it may be necessary for one mobile host to enlist the aid of other hosts in forwarding a packet to its destination, due to the limited range of each mobile host’s wireless transmissions. This paper presents a protocol for routing in ad hoc networks that uses dynamic source routing. The protocol adapts quickly to routing changes when host movement is frequent, yet requires little or no overhead during periods in which hosts move less frequently. Based on results from a packet-level simulation of mobile hosts operating in an ad hoc network, the protocol performs well over a variety of environmental conditions such as host density and movement rates. For all but the highest rates of host movement simulated, the overhead of the protocol is quite low, falling to just 1% of total data packets transmitted for moderate movement rates in a network of 24 mobile hosts. In all cases, the difference in length between the routes used and the optimal route lengths is negligible, and in most cases, route lengths are on average within a factor of 1.01 of optimal.

Highly dynamic Destination-Sequenced Distance-Vector routing (DSDV) for mobile computers

Abstract: An ad-hoc network is the cooperative engagement of a collection of Mobile Hosts without the required intervention of any centralized Access Point. In this paper we present an innovative design for the operation of such ad-hoc networks. The basic idea of the design is to operate each Mobile Host as a specialized router, which periodically advertises its view of the interconnection topology with other Mobile Hosts within the network. This amounts to a new sort of routing protocol. We have investigated modifications to the basic Bellman-Ford routing mechanisms, as specified by RIP [5], to make it suitable for a dynamic and self-starting network mechanism as is required by users wishing to utilize ad hoc networks. Our modifications address some of the previous objections to the use of Bellman-Ford, related to the poor looping properties of such algorithms in the face of broken links and the resulting time dependent nature of the interconnection topology describing the links between the Mobile Hosts. Finally, we describe the ways in which the basic network-layer routing can be modified to provide MAC-layer support for ad-hoc networks.

An architecture for wide-area multicast routing

Abstract: Existing multicast routing mechanisms were intended for use within regions where a group is widely represented or bandwidth is universally plentiful. When group members, and senders to those group members, are distributed sparsely across a wide area, these schemes are not efficient; data packets or membership report information are occasionally sent over many links that do not lead to receivers or senders, respectively. We have developed a multicast routing architecture that efficiently establishes distribution trees across wide area internets, where many groups will be sparsely represented. Efficiency is measured in terms of the state, control message processing, and data packet processing, required across the entire network in order to deliver data packets to the members of the group.Our Protocol Independent Multicast (PIM) architecture: (a) maintains the traditional IP multicast service model of receiver-initiated membership; (b) can be configured to adapt to different multicast group and network characteristics; (c) is not dependent on a specific unicast routing protocol; and (d) uses soft-state mechanisms to adapt to underlying network conditions and group dynamics. The robustness, flexibility, and scaling properties of this architecture make it well suited to large heterogeneous inter-networks.

The turn model for adaptive routing

Abstract: This paper presents a model for designing wormhole routing algorithms. A unique feature of the model is that it is not based on adding physical or virtual channels to direct networks (although it can be applied to networks with extra channels). Instead, the model is based on analyzing the directions in which packets can turn in a network and the cycles that the turns can form. Prohibiting just enough turns to break all of the cycles produces routing algorithms that are deadlock free, livelock free, minimal or nonminimal, and highly adaptive. This paper focuses on the two most common network topologies for wormhole routing, n-dimensional meshes and k-ary n-cubes without extra channels

Reliable transport protocol for internetwork routing

Abstract: A reliable transport protocol, suitable for routing protocols, that works with unicast transmission and multicast transmission, and an improved routing protocol based thereon. Multicast transmissions can be interspersed with unicast transmissions in situations where some of the receivers have received all of the packets sent to them and others have not. A mechanism to deliver multicast packets quickly to some receivers, even when there are unacknowledged packets pending for other receivers. When a packet is multicast from a sender node to all of its neighbors, the sender puts the packet on a queue for each neighbor and retransmits the packet if an acknowledgement has not been received within a predetermined period of time. If the packet is retransmitted, it is transmitted as a unicast. The invention takes advantage of the fact that the sender already has to maintain state information to determine who has not received its packets. A technique for distributing routing information gathered by a router outside an autonomous system of routers using the same routing protocol. A metric calculated by an identical routing protocol or a different routing protocol may be distributed and used by routers in a different autonomous system. Packets may be labeled with authentication information or with an administrative tag that specifies a method of routing in response to policy considerations.

Deadlock-free multicast wormhole routing in 2-D mesh multicomputers

Abstract: Multicast communication services, in which the same message is delivered from a source node to an arbitrary number of destination nodes, are being provided in new-generation multicomputers. Broadcast is a special case of multicast in which a message is delivered to all nodes in the network. The nCUBE-2, a wormhole-routed hypercube multicomputer, provides hardware support for broadcast and a restricted form of multicast in which the destinations form a subcube. However, the broadcast routing algorithm adopted in the nCUBE-2 is not deadlock-free. In this paper, four multicast wormhole routing strategies for 2-D mesh multicomputers are proposed and studied. All of the algorithms are shown to be deadlock-free. These are the first deadlock-free multicast wormhole routing algorithms ever proposed. A simulation study has been conducted that compares the performance of these multicast algorithms under dynamic network traffic conditions in a 2-D mesh. The results indicate that a dual-path routing algorithm offers performance advantages over tree-based, multipath, and fixed-path algorithms. >

A Necessary and Sufficient Condition for Deadlock-Free Adaptive Routing in Wormhole Networks

Abstract: Deadlock avoidance is a key issue in wormhole networks. A first approach [8] consists of removing the cyclic dependencies between channels. Although this is a necessary and sufficient condition for deadlock-free deterministic routing, it is only a sufficient condition for deadlock-free adaptive routing. A more powerful approach [12] only requires the absence of cyclic dependencies on a connected channel subset. The remaining channels can be used in almost any way. In this paper, we propose a necessary and sufficient condition for deadlock-free adaptive routing. This condition is the key for the design of maximally adaptive routing algorithms with minimum restrictions. Some examples are given, showing the application of the new theory. In particular, we propose a partially adaptive routing algorithm for k-ary n-cubes which doubles the throughput without increasing the hardware complexity significantly.

Performance analysis of mesh interconnection networks with deterministic routing

Abstract: This paper develops detailed analytical performance models for k-ary n-cube networks with single-hit or infinite buffers, wormhole routing, and the nonadaptive deadlock-free routing scheme proposed by Dally and Seitz (1987). In contrast to previous performance studies of such networks, the system is modeled as a closed queueing network that: includes the effects of blocking and pipelining of messages in the network; allows for arbitrary source-destination probability distributions; and explicitly models the virtual channels used in the deadlock-free routing algorithm. The models are used to examine several performance issues for 2-D networks with shared-memory traffic. These results should prove useful for engineering high-performance systems based on low-dimensional k-ary n-cube networks. >

An adaptive and fault tolerant wormhole routing strategy for k -ary n -cubes

Abstract: The concept of virtual channels is extended to multiple virtual communication systems that provide adaptability and fault tolerance in addition to being deadlock-free. A channel dependency graph is taken as the definition of what connections are possible, and any routing function must use only those connections defined by it. Virtual interconnection networks allowing adaptive, deadlock-free routing are examined for three k-ary n-cube topologies: unidirectional, torus-connected bidirectional, and mesh-connected bidirectional. >

Adaptive deadlock- and livelock-free routing with all minimal paths in torus networks

Abstract: This paper consists of two parts. In the first part, two new algorithms for deadlock- and livelock-free wormhole routing in the torus network are presented. The first algorithm, called Channels, is for the n-dimensional torus network. This technique is fully-adaptive minimal, that is, all paths with a minimal number of hops from source to destination are available for routing, and needs only five virtual channels per bidirectional link, the lowest channel requirement known in the literature for fully-adaptive minimal worm-hole routing. In addition, this result also yields the lowest buffer requirement known in the literature for packet-switched fully-adaptive minimal routing. The second algorithm, called 4-Classes, is for the bidimensional torus network. This technique is fully-adaptive minimal and requires only eight virtual channels per bidirectional link. Also, it allows for a highly parallel implementation of its associated routing node. In the second part of this paper, four worm-hole routing techniques for the two-dimensional torus are experimentally evaluated using a dynamic message injection model and different traffic patterns and message lengths. >

On-line admission control and circuit routing for high performance computing and communication

Abstract: This paper considers the problems of admission control and virtual circuit routing in high performance computing and communication systems. Admission control and virtual circuit routing problems arise in numerous applications, including video-servers, real-lime database servers, and the provision of permanent virtual channel in large-scale communications networks. The paper describes both upper and lower bounds on the competitive ratio of algorithms for admission control and virtual circuit routing in trees, arrays, and hypercubes (the networks most commonly used in conjunction with nigh performance computing and communication). Our results include optimal algorithms for admission control and virtual circuit routing in trees, as well as the first competitive algorithms for these problems on non-tree networks. A key result of our research is the development of on-line algorithms that substantially outperform the greedy-based approaches that are used in practice. >

Compressionless routing: a framework for adaptive and fault-tolerant routing

Abstract: Compressionless Routing (GR) is a new adaptive routing framework which provides a unified framework for efficient deadlock-free adaptive routing and fault-tolerance. CR exploits the tight-coupling between wormhole routers for flow control to detect potential deadlock situations and recover from them. Fault-tolerant Compressionless Routing (FCR) extends Compressionless Routing to support end-to-end fault-tolerant delivery. Detailed routing algorithms, implementation complexity and performance simulation results for CR and FCR are presented.CR has the following advantages: deadlock-free adaptive routing in torus networks with no virtual channels, simple router designs, order-preserving message transmission, applicability to a wide variety of network topologies, and elimination of the need for buffer allocation messages. FCR has the following advantages: tolerates transient faults while maintaining data integrity (nonstop fault-tolerance), tolerates permanent faults, can be applied to a wide variety of network topologies, and eliminates the need for software buffering and retry for reliability. These advantages of CR and FCR not only simplify hardware support for adaptive routing and fault-tolerance, they also can simplify communication software layers.

Static routing system

Abstract: A desired static route is read from a static routing table and a polling is effected on a network connected to a terminal at regular intervals. If a normal response is issued from the network, then information about the above static route is entered in a routing table. If no normal response is delivered from the network, then the information about the static routes entered in the routing table is deleted.

Performance Evaluation of Adaptive Routing Algorithms for k-ary-n-cubes

Abstract: Deadlock avoidance is a key issue in wormhole networks. A first approach [9] consists in removing the cyclic dependencies between channels. Although the absence of cyclic dependencies is a necessary and sufficient condition for deadlock-free deterministic routing, it is only a sufficient condition for deadlock-free adaptive routing. A more powerful approach [12] only requires the absence of cyclic dependencies on a connected channel subset. Moreover, we proposed a necessary and sufficient condition for deadlock-free adaptive routing [15].

Routing method for a hierarchical communications network, and a hierarchical communications network having improved routing

Abstract: A method and apparatus for selecting routes in a hierarchical communications network wherein a number of mutually isolated areas are provided at a first level, which areas are mutually linked at a second level. In the network, routing devices are provided at both levels. For selecting a route from a first area to a second area, use is made of routing information stored in the routing devices of the first level, relating to the first level and to reaching the nearest routing device of the second level. Use is also made, in the routing devices of the first level, of routing information relating to the second level.

Efficient fully adaptive wormhole routing in n-dimensional meshes

Abstract: An efficient fully adaptive wormhole routing algorithm for n-dimensional meshes is developed. The routing algorithm provides full adaptivity at a cost of one additional virtual channel per physical channel irrespective of the number of dimensions of the network. The algorithm is based on dividing the network graph into two acyclic graphs that contain all of the physical channels in the system. Virtual channels are classified as either waiting or nonwaiting channels. Busy channels that a message waits for to become available are classified as waiting channels, otherwise they are classified as nonwaiting channels. Thus, a message considers nonwaiting channels first to reach its destination. If all non-waiting channels are busy, the message considers waiting channels. Messages acquire waiting channels in two phases. In each phase, waiting channels belonging to one acyclic network graph are traversed. This 2-phase routing algorithm could be either minimal or nonminimal. However, we concentrate on minimal routing. It is demonstrated that this adaptive routing algorithm can utilize the virtual paths (channels) between any two nodes more efficiently than any of the present algorithms with the same hardware requirement. >

Multicast routing in self-routing multistage networks

Abstract: The authors present a study on multicast routing algorithms for the self-routing multistage networks. This work is based on the use of the cube concept which consists of a group of outlets reachable in one pass through the network. A multicast connection is decomposed into associated cubes such that each cube can be self-routed through the network. The context of this work is a recursive scheme for multistage network where the outlets are fed back to the inlets through external links. Three routing algorithms are proposed. The emphasis is on evaluating the performance of those algorithms in terms of two metrics. Extensive results from analysis and simulations are given to derive insights into the performance of the proposed routing algorithms. >

MDP routing in ATM networks using virtual path concept

Abstract: The virtual path (VP) concept has been proposed to simplify traffic control and resource management in future B-ISDN. In particular, call setup processing can be significantly reduced when resources are reserved on VPs. However, this advantage is offset by a decrease in statistical multiplexing gains of the networks. The focus of this paper is on how to improve bandwidth efficiency through adaptive routing when capacity is reserved on all VPs. The authors first examine two VP capacity reservation strategies. They then design and evaluate computationally feasible Markov decision process-based routing algorithms and show that the network blocking probability can be significantly reduced by MDP routing. >

Optimum routing of multicast streams

Abstract: The authors show that the problem of optimally routing multicast streams can be formulated as an integer programming problem. They propose an efficient solution technique, composed of two parts: (i) an extension to the decomposition principle, to speed up the linear relaxation of the problem, and (ii) enhanced value-fixing rules, to prune the search space for the integer problem. They characterize the reduction in run time gained using these techniques. Finally, they compare the run times for the optimum multicast routing algorithm and for existing heuristic algorithms. >

A theory of fault-tolerant routing in wormhole networks

Abstract: Fault-tolerant systems aim at providing continuous operations in the presence of faults. Multicomputers rely on an interconnection network between processors to support the message-passing mechanism. Therefore, the reliability of the interconnection network is very important for the reliability of the whole system. This paper analyzes the effective redundancy available in a wormhole network by combining connectivity and deadlock freedom. Redundancy is defined at the channel level. We propose a sufficient condition for channel redundancy, also computing the set of redundant channels. The redundancy level of the network is also defined, proposing a theorem that supplies its value. This theory is developed on top of our necessary and sufficient condition for deadlock-free adaptive routing. Finally, a fault-tolerant routing algorithm for n-dimensional meshes is proposed.

Fast algorithms for routing around faults in multibutterflies and randomly-wired splitter networks

Abstract: Simple deterministic O(log N)-step algorithms for routing permutations of packets in multibutterflies and randomly wired splitter networks are described. The algorithms are robust against faults (even in the worst case), and are efficient from a practical point of view. As a consequence, it is found that the multibutterfly is an excellent candidate for a high-bandwidth low-diameter switching network underlying a shared-memory machine. >

Node management in scalable distributed computing enviroment

Abstract: A method for independently executing software components in a node of a network containing many nodes. The method including generating a logical hierarchy of the roles of the nodes where any node can assume one or multiple roles; and negotiating the role of the nodes when there is a change in the configuration of the network. Another technique locates resources requested by a node in a scalable system interconnecting many nodes in a network. The technique includes identifying resources that join the network by switching from an inactive to an active state; and informing the requester the availability of the requested resource. A further technique determines routing paths in a context bridge which is able to route packets between nodes. The technique includes setting up a list of context bridges; listening for routing information packets which are periodically broadcast by other context bridges; and updating the database using the information contained in the received routing information packets. One more technique is on routing packets from a source node to a destination node using a context bridge. The technique includes determining whether the destination node has a routable protocol; if it does not have, then routing the packet using a source route containing the address of the context bridges from the source to the destination; and if it has, then routing the packet through at least one context bridge containing routable protocols.

Controlling alternate routing in general-mesh packet flow networks

Abstract: High-speed packet networks will begin to support services that need Quality-of-Service (QoS) guarantees. Guaranteeing QoS typically translates to reserving resources for the duration of a call. We propose a state-dependent routing scheme that builds on any base state-independent routing scheme, by routing flows which are blocked on their primary paths (as selected by the state-independent scheme) onto alternate paths in a manner that is guaranteed—under certain Poisson assumptions— to improve on the performance of the base state-independent scheme. Our scheme only requires each node to have state information of those links that are incident on it. Such a scheme is of value when either the base state-independent scheme is already in place and a complete overhaul of the routing algorithm is undesirable, or when the state (reserved flows) of a link changes fast enough that the timely update of state information is infeasible to all possible call-originators. The performance improvements due to our controlled alternate routing scheme are borne out from simulations conducted on a fully-connected 4-node network, as well as on a sparsely-connected 12-node network modeled on the NSFNet T3 Backbone.

An Efficient Zero-Skew Routing Algorithm

Abstract: A bucket algorithm is proposed for zero-skew routing with linear time complexity on the average. Our algorithm is much simpler and more efficient than the best known algorithm which uses Delaunay triangulations for segments on Manhattan distance. Experimental results show that the linearity of our algorithm is accomplished. Our algorithm generates a zero-skew routing for 3000-pin benchmark data within 5 seconds on a 90MIPS RISC workstation.

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

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 hypercube, the two-dimensional mesh, and the shuffle-exchange. Although the new techniques are designed for packet routing, they can be used alternatively for virtual cut-through routing models. The techniques presented for hypercubes and meshes are fully-adaptive and minimal. A fully-adaptive and minimal routing is one in which all possible minimal paths between 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. All of the new techniques are completely free of deadlock situations. >

Fault-tolerant wormhole routing in tori

Abstract: We present a method to enhance wormhole routing algorithms for deadlock-free fault-tolerant routing in tori. We consider arbitrarily-located faulty blocks and assume only local knowledge of faults. Messages are routed via shortest paths when there are no faults, and this constraint is only slightly relaxed to facilitate routing in the presence of faults. The key concept we use is that, for each fault region, a fault ring consisting of fault free nodes and physical channels can be formed around it. These fault rings can be used to route messages around fault regions. We prove that at most four additional virtual channels are sufficient to make any fully-adaptive algorithm tolerant to multiple faulty blocks in torus networks. As an example of this technique, we present simulation results for a fully-adaptive algorithm and show that good performance can be obtained with as many as 10% links faulty.

Minimising packet copies in multicast routing by exploiting geographic spread

Abstract: Routing connections in a point-to-point network is typically treated as a shortest path problem in a graph. Nodes represent switching systems, edges represent links and the edge lengths represent the costs associated with using a link. With multicast routing, one is interested in the shortest subtree of the network containing a given set of hosts. This is essentially a Steiner Tree problem in graphs and is known to be NP-complete [Karp]. Traditionally, the multicast routing algorithms proposed for packet switched networks like asynchronous transfer mode (ATM) networks have been aimed at minimising the total link cost of the Steiner tree [Waxman88], [Jaffe83] and do not take the geographical spreading of the connections into account. A dynamic point-to-multipoint routing algorithm is proposed, which takes into account the concept of geographic spread (also defined) of the connections and its performance is evaluated against the KMB near optimal heuristic algorithm for solving the Steiner tree problem [Kou].

A new global routing algorithm for FPGAs

Abstract: As in traditional ASIC technologies, FPGA routing usually consists of two steps: global routing and detailed routing. Unlike existing FPGA detailed routers, which can take full advantage of the special structures of the programmable routing resources, FPGA global routing algorithms still greatly resemble their counterparts in the traditional ASIC technologies. In particular, the routing congestion information of a switch block essentially is still measured by the numbers of available rows and columns in the switch block. Since the internal architecture of a switch block decides what can route through the block, the traditional measure of routing capacity is no longer accurate. In this paper, we present an accurate measure of switch block routing capacity. Our new measure considers the exact positions of the switches inside a switch block. Experiments with a global router based on these ideas show an average improvement of 38% in the channel width required to route some benchmark circuits using a popular switch block, compared with an algorithm based on the traditional methods for congestion control.

Single-layer global routing

Abstract: We introduce the single-layer global routing problem (SLGRP), also called homotopic routing or rubber-band-equivalent routing, and propose a technique for solving it. Given a set of nets, the proposed technique first determines the routing sequence based on the estimated congestion, the bounding-box length and priority. Then, it finds a routing path, being a sequence of tiles, for each net (one net at a time), avoiding "congested" areas. The overall goal of the algorithm is to maximize the number of routed nets. The proposed global router is the first true single-layer global router ever reported in the literature. The size of tiles, w/spl times/w, is an input parameter in our algorithm. For w=1, the proposed global router serves as an effective detailed router. An optimal postprocessing algorithm, minimizing wire length and number of bends, under homotopic transformation, is presented. The technique has been implemented and tried out for randomly generated data. The algorithm is very efficient and produces good results. >

Optimal Broadcast in All-Port Wormhole-Routed Hypercubes

Abstract: We give an optimal algorithm that broadcasts on an n-dimensional hypercube in Theta(n/ log_{2}(n+ 1)) routing steps with wormhole, e-cube routing and all-port communication. Previously, the best algorithm of McKinley and Trefftz requires [n/2] routing steps. We also give routing algorithms that achieve tight time bounds for n leqslant 7.