Showing papers on "Load balancing (computing) published in 2006"

Fast and memory-efficient regular expression matching for deep packet inspection

Abstract: Packet content scanning at high speed has become extremely important due to its applications in network security, network monitoring, HTTP load balancing, etc. In content scanning, the packet payload is compared against a set of patterns specified as regular expressions. In this paper, we first show that memory requirements using traditional methods are prohibitively high for many patterns used in packet scanning applications. We then propose regular expression rewrite techniques that can effectively reduce memory usage. Further, we develop a grouping scheme that can strategically compile a set of regular expressions into several engines, resulting in remarkable improvement of regular expression matching speed without much increase in memory usage. We implement a new DFA-based packet scanner using the above techniques. Our experimental results using real-world traffic and patterns show that our implementation achieves a factor of 12 to 42 performance improvement over a commonly used DFA- based scanner. Compared to the state-of-art NFA-based implementation, our DFA-based packet scanner achieves 50 to 700 times speedup.

A fuzzy multiobjective approach for network reconfiguration of distribution systems

Abstract: This paper presents an algorithm for network reconfiguration based on the heuristic rules and fuzzy multiobjective approach. Multiple objectives are considered for load balancing among the feeders and also to minimize the real power loss, deviation of nodes voltage, and branch current constraint violation, while subject to a radial network structure in which all loads must be energized. These four objectives are modeled with fuzzy sets to evaluate their imprecise nature and one can provide his or her anticipated value of each objective. Heuristic rules are also incorporated in the algorithm for minimizing the number of tie-switch operations. The effectiveness of the proposed method is demonstrated through an example.

Avoiding traceroute anomalies with Paris traceroute

Abstract: Traceroute is widely used, from the diagnosis of network problems to the assemblage of internet maps. However, there are a few serious problems with this tool, in particular due to the presence of load balancing routers in the network. This paper describes a number of anomalies that arise in nearly all traceroute-based measurements. We categorize them as "loops", "cycles", and "diamonds". We provide a new publicly-available traceroute, called Paris traceroute, which controls packet header contents to obtain a more precise picture of the actual routes that packets follow. This new tool allows us to find conclusive explanations for some of the anomalies, and to suggest possible causes for others.

MobiRoute: routing towards a mobile sink for improving lifetime in sensor networks

Abstract: Improving network lifetime is a fundamental challenge of wireless sensor networks. One possible solution consists in making use of mobile sinks. Whereas theoretical analysis shows that this approach does indeed benefit network lifetime, practical routing protocols that support sink mobility are still missing. In this paper, in line with our previous efforts, we investigate the approach that makes use of a mobile sink for balancing the traffic load and in turn improving network lifetime. We engineer a routing protocol, MobiRoute, that effectively supports sink mobility. Through intensive simulations in TOSSIM with a mobile sink and an implementation of MobiRoute, we prove the feasibility of the mobile sink approach by demonstrating the improved network lifetime in several deployment scenarios.

Parallel hypergraph partitioning for scientific computing

Abstract: Graph partitioning is often used for load balancing in parallel computing, but it is known that hypergraph partitioning has several advantages. First, hypergraphs more accurately model communication volume, and second, they are more expressive and can better represent nonsymmetric problems. Hypergraph partitioning is particularly suited to parallel sparse matrix-vector multiplication, a common kernel in scientific computing. We present a parallel software package for hypergraph (and sparse matrix) partitioning developed at Sandia National Labs. The algorithm is a variation on multilevel partitioning. Our parallel implementation is novel in that it uses a two-dimensional data distribution among processors. We present empirical results that show our parallel implementation achieves good speedup on several large problems (up to 33 million nonzeros) with up to 64 processors on a Linux cluster.

A Client-Driven Approach for Channel Management in Wireless LANs

Abstract: We propose an efficient client-based approach for channel management (channel assignment and load balancing) in 802.11-based WLANs that lead to better usage of the wireless spectrum. This approach is based on a “conflict set coloring” formulation that jointly performs load balancing along with channel assignment. Such a formulation has a number of advantages. First, it explicitly captures interference effects at clients. Next, it intrinsically exposes opportunities for better channel re-use. Finally, algorithms based on this formulation do not depend on specific physical RF models and hence can be applied efficiently to a wide-range of in-building as well as outdoor scenarios. We have performed extensive packet-level simulations and measurements on a deployed wireless testbed of 70 APs to validate the performance of our proposed algorithms. We show that in addition to single network scenarios, the conflict set coloring formulation is well suited for channel assignment where multiple wireless networks share and contend for spectrum in the same physical space. Our results over a wide range of both simulated topologies and in-building testbed experiments indicate that our approach improves application level performance at the clients by upto three times (and atleast 50%) in comparison to current best-known techniques.

Cross-Layer Design for Lifetime Maximization in Interference-Limited Wireless Sensor Networks

Abstract: We consider the joint optimal design of the physical, medium access control (MAC), and routing layers to maximize the lifetime of energy-constrained wireless sensor networks. The problem of computing lifetime-optimal routing flow, link schedule, and link transmission powers for all active time slots is formulated as a non-linear optimization problem. We first restrict the link schedules to the class of interference-free time division multiple access (TDMA) schedules. In this special case, we formulate the optimization problem as a mixed integerconvex program, which can be solved using standard techniques. Moreover, when the slots lengths are variable, the optimization problem is convex and can be solved efficiently and exactly using interior point methods. For general non-orthogonal link schedules, we propose an iterative algorithm that alternates between adaptive link scheduling and computation of optimal link rates and transmission powers for a fixed link schedule. The performance of this algorithm is compared to other design approaches for several network topologies. The results illustrate the advantages of load balancing, multihop routing, frequency reuse, and interference mitigation in increasing the lifetime of energy-constrained networks. We also briefly discuss computational approaches to extend this algorithm to large networks

Server load balancing using IP option field approach to identify route to selected server

Abstract: A router for routing data from a client through load-balancing nodes to a selected load-balanced server among a plurality of servers in a network involves: receiving, at a last load balancing node associated with a selected server among the plurality of servers, a first packet of a server reply to a request from the client; storing identifiers of ingress interfaces on which the packet arrives, in a send path list for server load balancing, as the first packet of the server reply is routed from the last load balancing node to the client using hop-by-hop decisions; receiving subsequent packets of the client request; and forwarding the subsequent packets to the selected server only on a route that is defined by the send path list and without hop-by-hop routing decisions. Packet flows are routed from the same client to the same server without hop-by-hop routing decisions or repeated load-balancing decisions.

Load balancing a data storage system

Abstract: An apparatus and method for automatically load balancing one or more workload groups to a set of available physical resources of a data storage system, and generating a layout planning recommendation of the set of available physical resources that supports the one or more workload groups based on the load balancing.

Geo-locating load balancing

Abstract: Methods and apparatus are provided for geo-locating load balancing. According to one embodiment, a communication network architecture includes multiple servers, multiple load balancers, and multiple geographically dispersed communication devices. The servers provide services to the communication devices within the communication network. The load balancers each service a shared virtual Internet Protocol (IP) address common to all of the load balancers and perform load balancing of service requests on behalf of two or more of the servers that are located geographically proximate to the load balancer. The communication devices are communicatively coupled with the load balancers and are configured to issue service requests intended for any of the servers to the shared virtual IP address, whereby, upon issuing a service request, a communication device is directed to a particular server selected by a load balancing routine that is associated with a load balancer that is closest to the communication device.

Supporting Task Migration in Multi-Processor Systems-on-Chip: A Feasibility Study

Abstract: With the advent of multi-processor systems-on-chip, the interest in process migration is again on the rise both in research and in product development. New challenges associated with the new scenario include increased sensitivity to implementation complexity, tight power budgets, requirements on execution predictability, and the lack of virtual memory support in many low-end MPSoCs. As a consequence, effectiveness and applicability of traditional transparent migration mechanisms are put in discussion in this context. Our paper proposes a task management software infrastructure that is well suited for the constraints of single chip multiprocessors with distributed operating systems. Load balancing in the system is maintained by means of intelligent initial placement and task migration. We propose a user-managed migration scheme based on code check pointing and user-level middleware support as an effective solution for many MPSoC application domains. In order to prove the practical viability of this scheme, we also propose a characterization methodology for task migration overhead. We derive the minimum execution time following a task migration event during which the system configuration should be frozen to make up for the migration cost

Congestion Avoidance Based on Lightweight Buffer Management in Sensor Networks

Abstract: A wireless sensor network is constrained by computation capability, memory space, communication bandwidth, and above all, energy supply. When a critical event triggers a surge of data generated by the sensors, congestion may occur as data packets converge toward a sink. Congestion causes energy waste, throughput reduction, and information loss. However, the important problem of congestion avoidance in sensor networks is largely open. This paper proposes a congestion-avoidance scheme based on lightweight buffer management. We describe simple yet effective approaches that prevent data packets from overflowing the buffer space of the intermediate sensors. These approaches automatically adapt the sensors' forwarding rates to nearly optimal without causing congestion. We discuss how to implement buffer-based congestion avoidance with different MAC protocols. In particular, for CSMA with implicit ACK, our 1/k-buffer solution prevents hidden terminals from causing congestion. We demonstrate how to maintain near-optimal throughput with a small buffer at each sensor and how to achieve congestion-free load balancing when there are multiple routing paths toward multiple sinks

Systems and Methods for Migrating Components in a Hierarchical Storage Network

Abstract: System and methods for selectively or automatically migrating resources between storage operation cells are provided. In accordance with one aspect of the invention, a management component within the storage operation system may monitor system operation and migrate components from storage operation cell to another to facilitate failover recovery, promote load balancing within the system and improve overall system performance as further described herein. Another aspect of the invention may involve performing certain predictive analyses on system operation to reveal trends and tendencies within the system. Such information may be used as the basis for potentially migrating components from one storage operation cell to another to improve system performance and reduce or eliminate resource exhaustion or congestion conditions.

VBI-Tree: A Peer-to-Peer Framework for Supporting Multi-Dimensional Indexing Schemes

Abstract: Multi-dimensional data indexing has received much attention in a centralized database. However, not so much work has been done on this topic in the context of Peerto- Peer systems. In this paper, we propose a new Peer-to- Peer framework based on a balanced tree structure overlay, which can support extensible centralized mapping methods and query processing based on a variety of multidimensional tree structures, including R-Tree, X-Tree, SSTree, and M-Tree. Specifically, in a network with N nodes, our framework guarantees that point queries and range queries can be answered within O(logN) hops. We also provide an effective load balancing strategy to allow nodes to balance their work load efficiently. An experimental assessment validates the practicality of our proposal.

Load balancing communications system comprising cellular overlay and ad hoc networks

Abstract: The present invention relates to a method and system for balancing load in a network environment comprising at least one ad hoc network and at least one overlay network (10) , wherein at least one wireless mobile node (50) of the ad hoc network is selected as a head node for collecting transmission related information received from other mobile nodes of said ad hoc network, which is reported to a load balancing function of the network environment. There, the reported transmission related information is analyzed and a connection link within the network environment is selected based on the result of said analyzing step.

Simple Efficient Load-Balancing Algorithms for Peer-to-Peer Systems

Abstract: Load balancing is a critical issue for the efficient operation of peer-to-peer (P2P) networks. We give two new load-balancing protocols whose provable performance guarantees are within a constant factor of optimal. Our protocols refine the consistent hashing data structure that underlies the Chord (and Koorde) P2P network. Both preserve Chord's logarithmic query time and near-optimal data migration cost.Consistent hashing is an instance of the distributed hash table (DHT) paradigm for assigning items to nodes in a P2P system: items and nodes are mapped to a common address space, and nodes have to store all items residing closeby in the address space.Our first protocol balances the distribution of the key address space to nodes, which yields a load-balanced system when the DHT maps items "randomly" into the address space. To our knowledge, this yields the first P2P scheme simultaneously achieving O(log n) degree, O(log n) look-up cost, and constant-factor load balance (previous schemes settled for any two of the three).Our second protocol aims to balance directly the distribution of items among the nodes. This is useful when the distribution of items in the address space cannot be randomized. We give a simple protocol that balances load by moving nodes to arbitrary locations "where they are needed." As an application, we use the last protocol to give an optimal implementation of a distributed data structure for range searches on ordered data.

Providing resiliency to load variations in distributed stream processing

Abstract: Scalability in stream processing systems can be achieved by using a cluster of computing devices. The processing burden can, thus, be distributed among the nodes by partitioning the query graph. The specific operator placement plan can have a huge impact on performance. Previous work has focused on how to move query operators dynamically in reaction to load changes in order to keep the load balanced. Operator movement is too expensive to alleviate short-term bursts; moreover, some systems do not support the ability to move operators dynamically. In this paper, we develop algorithms for selecting an operator placement plan that is resilient to changes in load. In other words, we assume that operators cannot move, therefore, we try to place them in such a way that the resulting system will be able to withstand the largest set of input rate combinations. We call this a resilient placement.This paper first formalizes the problem for operators that exhibit linear load characteristics (e.g., filter, aggregate), and introduces a resilient placement algorithm. We then show how we can extend our algorithm to take advantage of additional workload information (such as known minimum input stream rates). We further show how this approach can be extended to operators that exhibit non-linear load characteristics (e.g., join). Finally, we present prototype- and simulation-based experiments that quantify the benefits of our approach over existing techniques using real network traffic traces.

Layered routing in irregular networks

Abstract: Freedom from deadlock is a key issue in cut-through, wormhole, and store and forward networks, and such freedom is usually obtained through careful design of the routing algorithm. Most existing deadlock-free routing methods for irregular topologies do, however, impose severe limitations on the available routing paths. We present a method called layered routing, which gives rise to a series of routing algorithms, some of which perform considerably better than previous ones. Our method groups virtual channels into network layers and to each layer it assigns a limited set of source/destination address pairs. This separation of traffic yields a significant increase in routing efficiency. We show how the method can be used to improve the performance of irregular networks, both through load balancing and by guaranteeing shortest-path routing. The method is simple to implement, and its application does not require any features in the switches other than the existence of a modest number of virtual channels. The performance of the approach is evaluated through extensive experiments within three classes of technologies. These experiments reveal a need for virtual channels as well as an improvement in throughput for each technology class.

Throughput-range tradeoff of wireless mesh backhaul networks

Abstract: Wireless backhaul communication is expected to play a significant role in providing the necessary backhaul resources for future high-rate wireless networks. Mesh networking, in which information is routed from source to destination over multiple wireless links, has potential advantages over traditional single-hop networking, especially for backhaul communication. We develop a linear programming framework for determining optimum routing and scheduling of flows that maximizes throughput in a wireless mesh network and accounts for the effect of interference and variable-rate transmission. We then apply this framework to examine the throughput and range capabilities for providing wireless backhaul to a hexagonal grid of base stations, for both single-hop and multihop transmissions for various network scenarios. We then discuss the application of mesh networking for load balancing of wired backhaul traffic under unequal access traffic conditions. Numerical results show a significant benefit for mesh networking under unbalanced loading.

Method providing server affinity and client stickiness in a server load balancing device without TCP termination and without keeping flow states

Abstract: A method of routing data from a client through one or more load-balancing routers to a selected load-balanced server among a plurality of servers in a network involves: receiving, at a load balancing node in a path from the client to the plurality of servers, a first packet of a request from a client; creating and storing a mapping of flow identifying information, associated with the first packet, to a client stickiness identifier; pushing the client stickiness label into a sending path list that is stored in association with the first packet; storing the client stickiness label in a mapping of client stickiness labels to server identifiers at a last load balancing node associated with the plurality of servers, wherein the mapping associates the client stickiness label with a server identifier that uniquely identifies a selected server that has been selected from among the plurality of servers to receive the client request; and forwarding all subsequent packets associated with the client request to the same selected server based on looking up the client stickiness label of such subsequent packets in the mapping As a result, packet flows are rapidly routed from the same client to the same server without time-consuming hop-by-hop routing decisions or repeated load-balancing decisions

Integrated Radio Resource Allocation for Multihop Cellular Networks With Fixed Relay Stations

Abstract: Recently, the notion that a logical next step towards future mobile radio networks is to introduce multihop relaying into cellular networks, has gained wide acceptance. Nevertheless, due to the inherent drawbacks of multihop relaying, e.g., the requirement for extra radio resources for relaying hops, and the sensitivity to the quality of relaying routes, multihop cellular networks (MCNs) require a well-designed radio resource allocation strategy in order to secure performance gains. In this paper, the optimal radio resource allocation problem in MCNs, with the objective of throughput maximization, is formulated mathematically and proven to be NP-hard. Considering the prohibitive complexity of finding the optimal solution for such an NP-hard problem, we propose an efficient heuristic algorithm, named integrated radio resource allocation (IRRA), to find suboptimal solutions. The IRRA is featured as a low-complexity algorithm that involves not only base station (BS) resource scheduling, but also routing and relay station (RS) load balancing. Specifically, a load-based scheme is developed for routing. A mode-aware BS resource-scheduling scheme is proposed for handling links in different transmission modes, i.e., direct or multihop. Moreover, a priority-based RS load balancing approach is presented for the prevention of the overloading of RSs. Within the framework of the IRRA, the above three functions operate periodically with coordinated interactions. To prove the effectiveness of the proposed IRRA algorithm, a case study was carried out based on enhanced uplink UMTS terrestrial radio access/frequency-division duplex with fixed RSs. The IRRA is evaluated through system level simulations, and compared with two other cases: 1) nonrelaying and 2) relaying with a benchmark approach. The results show that the proposed algorithm can ensure significant gains in terms of cell throughput

Cell Breathing Techniques for Load Balancing in Wireless LANs

Abstract: Maximizing network throughput while providing fairness is one of the key challenges in wireless LANs (WLANs). This goal is typically achieved when the load of access points (APs) is balanced. Recent studies on operational WLANs, however, have shown that AP load is often substantially uneven. To alleviate such imbalance of load, several load balancing schemes have been proposed. These schemes commonly require proprietary software or hardware at the user side for controlling the user-AP association. In this paper we present a new load balancing technique by controlling the size of WLAN cells (i.e., AP’s coverage range), which is conceptually similar to cell breathing in cellular networks. The proposed scheme does not require any modification to the users neither the IEEE 802.11 standard. It only requires the ability of dynamically changing the transmission power of the AP beacon messages. We develop a set of polynomial time algorithms that find the optimal beacon power settings which minimize the load of the most congested AP. We also consider the problem of network-wide min-max load balancing. Simulation results show that the performance of the proposed method is comparable with or superior to the best existing association-based methods.

Dynamic Load Balancing Strategy for Grid Computing

Abstract: Workload and resource management are two essential functions provided at the service level of the grid software infras- tructure. To improve the global throughput of these software environ- ments, workloads have to be evenly scheduled among the available resources. To realize this goal several load balancing strategies and algorithms have been proposed. Most strategies were developed in mind, assuming homogeneous set of sites linked with homogeneous and fast networks. However for computational grids we must address main new issues, namely: heterogeneity, scalability and adaptability. In this paper, we propose a layered algorithm which achieve dynamic load balancing in grid computing. Based on a tree model, our algorithm presents the following main features: (i) it is layered; (ii) it supports heterogeneity and scalability; and, (iii) it is totally independent from any physical architecture of a grid.

Achieving Load Balancing in Wireless Mesh Networks Through Multiple Gateways

Abstract: Wireless Mesh Networks (WMNs) are evolving to be the key technology of the future As the WMNs are envisioned to provide high bandwidth broadband service to a large community of users, the Internet Gateway (IGW) which acts as a central point of internet attachment for the mesh routers, it is likely to be a potential bottleneck because of its limited wireless link capacity We propose a novel technique that elegantly balances the load among the different IGWs in a WMN We switch the point of attachment of an active source serviced gateway depending on the average queue length at the IGW The proposed load balancing scheme includes: an initial gateway discovery module, which determines a primary gateway for a mesh router and a load balancing module that rebalances the load among the gateways We use ns-2 [9] for evaluating our proposed scheme and we observe that the proposed scheme is able to balance the traffic efficiently

Network system, traffic balancing method, network monitoring device and host

Abstract: A traffic balancing system, traffic balancing device and traffic balancing method that converts IP packets by switching IP address of the destination host between the dual stack hosts communicating with each other, in order to control traffic balancing in the networks.

Transparent redirection and load-balancing in a storage network

Abstract: A storage system includes a plurality of storage servers that store a plurality of files, a monitor module, and a redirector module. The monitor module monitors usage information associated with the plurality of storage servers. The redirector module determines, based on the monitored usage information, a storage server in the plurality of storage servers to service a session from a client. The redirector module then instructs the client to establish the session with the determined storage server.

Grouping mesh clusters

Abstract: Systems and methods for grouping mesh networks. Mesh networks enable energy data to be transferred from an energy sensing device to a destination device using various networks and reduces the need to install metering stations. Embodiments of the invention join or group mesh networks that otherwise are not able to communicate. The connections between the grouped mesh networks can be passive using directional antennas or passive antennas or active using higher power RF devices, solar repeaters, mobile mesh devices, etc. The energy data is routed in a smart manner, by performing load balancing at gateways, by monitoring the signal to noise ratio of available communication paths, etc. Mesh clusters can also be created to define low power clusters, address blocking clusters, and frequency based clusters. Grouping clusters facilitates the efficient transfer of energy data from an energy sensing device to a energy management station.

Landmark-Based Information Storage and Retrieval in Sensor Networks

Abstract: For a wide variety of sensor network environments, location information is unavailable or expensive to obtain. We propose a location-free, lightweight, distributed, and data-centric storage/retrieval scheme for information producers and information consumers in sensor networks. Our scheme is built upon the Gradient Landmark-Based Distributed Routing protocol (GLIDER) [8], a two-level routing scheme where sensor nodes are partitioned into tiles by their graph distances to a small set of local landmarks so that localized and efficient routing can be achieved inside and across tiles. Our information storage and retrieval scheme uses two ideas on top of the GLIDER hierarchy — a distributed hash table on the combinatorial tile adjacency graph and a double-ruling scheme within each tile. Queries follow a path that will provably reach the data replicated by the producer(s). We show that this scheme compares favorably with previously proposed schemes, such as Geographic Hash Tables (GHT), providing comparable data storage performance and better locality-aware data retrieval performance. More importantly, this scheme uses no geographic information, makes few assumptions on the network model, and achieves better load balancing and structured data processing and aggregation even for sensor fields with complex geometric shapes and non-trivial topology.

Replication, load balancing and efficient range query processing in DHTs

Abstract: We consider the conflicting problems of ensuring data-access load balancing and efficiently processing range queries on peer-to-peer data networks maintained over Distributed Hash Tables (DHTs). Placing consecutive data values in neighboring peers is frequently used in DHTs since it accelerates range query processing. However, such a placement is highly susceptible to load imbalances, which are preferably handled by replicating data (since replication also introduces fault tolerance benefits). In this paper, we present HotRoD, a DHT-based architecture that deals effectively with this combined problem through the use of a novel locality-preserving hash function, and a tunable data replication mechanism which allows trading off replication costs for fair load distribution. Our detailed experimentation study shows strong gains in both range query processing efficiency and data-access load balancing, with low replication overhead. To our knowledge, this is the first work that concurrently addresses the two conflicting problems using data replication.