Browsing by Subject "Distributed systems"

Now showing 1 - 12 of 12

Open Access
AIMD-based online MPLS traffic engineering for TCP flows via distributed multi-path routing
(Springer, 2004) Alparslan O.; Akar, N.; Karasan, E.
With this paper, we propose a distributed online traffic engineering architecture for MPLS networks. In this architecture, a primary and secondary MPLS LSP are established from an ingress LSR to every other egress LSR. We propose to split the TCP traffic between the primary and secondary paths using a distributed mechanism based on ECN marking and AIMD-based rate control. Inspired by the random early detection mechanism for active queue management, we propose a random early reroute scheme to adaptively control the delay difference between the primary and secondary LSPS. Considering the adverse effect of packet reordering on TCP performance for packet-based load balancing schemes, we propose that the TCP splitting mechanism operates on a per-flow basis. Using flow-based models developed for Internet traffic and simulations, we show that flow-based distributed multi-path traffic engineering outperforms on a consistent basis the case of a single path in terms of per-flow goodputs. Due to the elimination of out-of-order packet arrivals, flow-based splitting also enhances TCP performance with respect to packet-based splitting especially for long TCP flows that are hit hard by packet reordering. We also compare and contrast two queuing architectures for differential treatment of data packets routed over primary and secondary LSPS in the MPLS data plane, namely first-in-first-out and strict priority queuing. We show through simulations that strict priority queuing is more effective and relatively more robust with respect to the changes in the traffic demand matrix than first-in-first-out queuing in the context of distributed multi-path routing.
Open Access
Auction based scheduling for distributed systems
(International Institute of Informatics and Systemics, 2006) Zarifoğlu, Emrah; Sabuncuoğlu, İhsan
Businesses deal with huge databases over a geographically distributed supply network. When this is combined with scheduling and planning needs, it becomes too difficult to handle. Recently, Fast Consumer Goods sector tends to consolidate their manufacturing facilities on a single supplier serving to a distributed customer network. This decentralized structure causes imperfect information sharing between customers and the supplier. We model this problem as a single machine distributed scheduling problem with job agents representing the customers and the machine agent representing the supplier. We developed Auction Based Algorithm by exploiting the opportunity to use game theoretic approach to solve the problem in the decentralized utility case. Results of our extensive computational experiments indicate that Auction Based Algorithm converges to the upper bound found for the total utility measure.
Open Access
A connection management protocol for promoting cooperation in Peer-to-Peer networks
(Elsevier BV, 2008-02-05) Karakaya, M.; Körpeoǧlu, I.; Ulusoy, Özgür
The existence of a high degree of free riding in Peer-to-Peer (P2P) networks is an important threat that should be addressed while designing P2P protocols. In this paper we propose a connection-based solution that will help to reduce the free riding effects on a P2P network and discourage free riding. Our solution includes a novel P2P connection type and an adaptive connection management protocol that dynamically establishes and adapts a P2P network topology considering the contributions of peers. The aim of the protocol is to bring contributing peers closer to each other on the adapted topology and to push the free riders away from the contributors. In this way contribution is promoted and free riding is discouraged. Unlike some other proposals against free riding, our solution does not require any permanent identification of peers or a security infrastructure for maintaining a global reputation system. It is shown through simulation experiments that there is a significant improvement in performance for contributing peers in a network that applies our protocol. © 2007 Elsevier B.V. All rights reserved.
Open Access
Distributed block formation and layout for disk-based management of large-scale graphs
(Springer, 2017) Yaşar, A.; Gedik, B.; Ferhatosmanoğlu, H.
We are witnessing an enormous growth in social networks as well as in the volume of data generated by them. An important portion of this data is in the form of graphs. In recent years, several graph processing and management systems emerged to handle large-scale graphs. The primary goal of these systems is to run graph algorithms and queries in an efficient and scalable manner. Unlike relational data, graphs are semi-structured in nature. Thus, storing and accessing graph data using secondary storage requires new solutions that can provide locality of access for graph processing workloads. In this work, we propose a scalable block formation and layout technique for graphs, which aims at reducing the I/O cost of disk-based graph processing algorithms. To achieve this, we designed a scalable MapReduce-style method called ICBL, which can divide the graph into a series of disk blocks that contain sub-graphs with high locality. Furthermore, ICBL can order the resulting blocks on disk to further reduce non-local accesses. We experimentally evaluated ICBL to showcase its scalability, layout quality, as well as the effectiveness of automatic parameter tuning for ICBL. We deployed the graph layouts generated by ICBL on the Neo4j open source graph database, http://www.neo4j.org/ (2015) graph database management system. Our results show that the layout generated by ICBL reduces the query running times over Neo4j more than 2 × compared to the default layout. © 2017, Springer Science+Business Media New York.
Open Access
Distributed output feedback control of decomposable LPV systems with delay and switching topology: application to consensus problem in multi-agent systems
(Taylor & Francis, 2020-01-08) Zakwan, Muhammad; Ahmed, Saeed
This paper presents distributed output feedback control of a class of distributed linear parameter varying systems with switching topology and parameter varying time delay. To formulate the synthesis conditions for the distributed controller in terms of LMIs, the delay dependent bounded-real lemma based on parameter-dependent Lyapunov–Krasovskii functionals is used. The efficacy of the result is illustrated by applying it to two real-world examples pertaining to the consensus problem of multi-agent systems.
Open Access
Multilevel heuristics for task assignment in distributed systems
(1998) İkinci, Murat
Task assignment problem deals with assigning tasks to processors in order to minimize the sum of execution and communication costs in a distributed system. In this work, we propose a novel task clustering scheme which considei s the differences between the execution times of tasks to be clustered as well as the communication costs between them. We use this clustering approach witli proper assignment schemes to implement two-phase assignment algorithms which can be used to find suboptimal solutions to any task assignment problem. In addition, we adapt the multilevel scheme used in graph/hypergrapli partitioning to the task assignment. Multilevel assignment algorithms reduce the size of the original problem by collapsing tasks, find an initial assignment on the smellier problem, and then projects it towards the original problem l)y successively refining the assignment at each level. We propose several clustering schemes for multilevel assignment algorithms. The performance of all proposed algorithms are evaluated through an experimental study where the assignment qualities are compared with two up-to-date heuristics. Experimerita.l results show that our algorithms substantially outperform both of the existing heuristics.
Open Access
Recurrent neural networks based online learning algorithms for distributed systems
(Institute of Electrical and Electronics Engineers, 2018) Ergen, Tolga; Şahin, S. Onur; Kozat, S. Serdar
In this paper, we investigate online parameter learning for Long Short Term Memory (LSTM) architectures in distributed networks. Here, we first introduce an LSTM based structure for regression. Then, we provide the equations of this structure in a state space form for each node in our network. Using this form, we then learn the parameters via our Distributed Particle Filtering based (DPF) training method. Our training method asymptotically converges to the optimal parameter set provided that we satisfy certain trivial requirements. While achieving this performance, our training method only causes a computational load that is similar to the efficient first order gradient based training methods. Through real life experiments, we show substantial performance gains compared to the conventional methods.
Open Access
Sequential nonlinear learning for distributed multiagent systems via extreme learning machines
(Institute of Electrical and Electronics Engineers Inc., 2017) Vanli, N. D.; Sayin, M. O.; Delibalta, I.; Kozat, S. S.
We study online nonlinear learning over distributed multiagent systems, where each agent employs a single hidden layer feedforward neural network (SLFN) structure to sequentially minimize arbitrary loss functions. In particular, each agent trains its own SLFN using only the data that is revealed to itself. On the other hand, the aim of the multiagent system is to train the SLFN at each agent as well as the optimal centralized batch SLFN that has access to all the data, by exchanging information between neighboring agents. We address this problem by introducing a distributed subgradient-based extreme learning machine algorithm. The proposed algorithm provides guaranteed upper bounds on the performance of the SLFN at each agent and shows that each of these individual SLFNs asymptotically achieves the performance of the optimal centralized batch SLFN. Our performance guarantees explicitly distinguish the effects of data-and network-dependent parameters on the convergence rate of the proposed algorithm. The experimental results illustrate that the proposed algorithm achieves the oracle performance significantly faster than the state-of-the-art methods in the machine learning and signal processing literature. Hence, the proposed method is highly appealing for the applications involving big data. © 2016 IEEE.
Open Access
Service rate region: A new aspect of coded distributed system design
(IEEE, 2021-10-04) Aktaş, Mehmet; Joshi, G.; Kadhe, S.; Kazemi, F.; Soljanin, E.
Erasure coding has been recognized as a powerful method to mitigate delays due to slow or straggling nodes in distributed systems. This work shows that erasure coding of data objects can flexibly handle skews in the request rates. Coding can help boost the service rate region , that is, increase the overall volume of data access requests that the system can handle. This paper aims to postulate the service rate region as an important consideration in the design of erasure-coded distributed systems. We highlight several open problems that can be grouped into two broad threads: 1) characterizing the service rate region of a given code and finding the optimal request allocation, and 2) designing the underlying erasure code for a given service rate region. As contributions along the first thread, we find the rate regions of maximum-distance-separable, locally repairable, and simplex codes. We show the effectiveness of hybrid codes that combine replication and erasure coding in terms of code design. We also discover fundamental connections between multi-set batch codes and the problem of maximizing the service rate region.
Open Access
SPL: an extensible language for distributed stream processing
(Association for Computing Machinery, 2017) Hirzel M.; Schneider S.; Gedik, B.
Big data is revolutionizing how all sectors of our economy do business, including telecommunication, transportation, medical, and finance. Big data comes in two flavors: data at rest and data in motion. Processing data in motion is stream processing. Stream processing for big data analytics often requires scale that can only be delivered by a distributed system, exploiting parallelism on many hosts and many cores. One such distributed stream processing system is IBM Streams. Early customer experience with IBM Streams uncovered that another core requirement is extensibility, since customers want to build high-performance domain-specific operators for use in their streaming applications. Based on these two core requirements of distribution and extensibility, we designed and implemented the Streams Processing Language (SPL). This article describes SPL with an emphasis on the language design, distributed runtime, and extensibility mechanism. SPL is now the gateway for the IBM Streams platform, used by our customers for stream processing in a broad range of application domains. © 2017 ACM.
Open Access
The Universal robot bus : a local communication infrastructure for small robots
(2008-12) Avcı, Akın
Design and construction of small autonomous mobile robots is a challenging task that involves the selection, interfacing and programming of a large number of sensor and actuator components. Facilitating this tedious process requires modularity and extensibility in both hardware and software components. This thesis concerns the development of a real-time infrastructural architecture called the Universal Robot Bus (URB), based on the popular Inter-Integrated Circuit (I 2C) bus standard. The main purpose of the URB is the rapid development and realtime interfacing of local nodes controlling small sensor and actuator components distributed on a mobile robot platform. It is designed to be very lightweight and efficient, with real-time support for RS232 or USB connections to a central computer. The URB infrastructure is inspired from the RiSEBus architecture, which is also an internal communication protocol for mobile robots, and developed to fit our requirements. URB offers a modular and extensible architecture for rapid and frequent changes to the platform design. Mobile robots also need to perform accurate sensory processing and estimation in order to operate in unstructured environments. Hence, the URB also supports real-time operations with reliable hardware and software components. The first novel contribution of this thesis is the design and implementation of automatic synchronization of data acquisition across multiple nodes. Our synchronization algorithm ensures that each node completes data acquisition tasks simultaneously well before read operations. Our experiments also prove that each individual node acquires data at approximately the same time instant. The second major contribution of this thesis is the incorporation of automated and unsupervised data acquisition across multiple nodes into the URB protocol. Autonomous data acquisition helps acquire periodic and frequently needed data over nodes. This enhancement reduces the computational load on the central processing unit and reduces bandwidth costs over the communication medium. This thesis also servers a survey on network architectures and protocols, network applications in robotics, synchronization algorithms, and applications of synchronization in robotics besides implementation details of the URB.
Open Access
An USB-based real-time communication infrastructure for robotic platforms
(2009) Öztürk, Cihan
A typical robot operates by carrying out a sequence of tasks, usually consisting of acquisition of sensory data, interpretation of sensory inputs for making decisions, and application of commands on appropriate actuators. Since this cycle involves transmission of data among electro-mechanical components of the robot, high quality communication is a fundamental requirement. Besides being reliable, robust, extensible, and efficient, a high quality communication infrastructure should satisfy all additional communication requirements that are specific to the robot it is used within. To give an example, for a rapid moving autonomous robot with a reactive controller which is intended to be used in time critical situations, a real-time communication infrastructure which guarantees demanded response times is required. The Universal Robot Bus (URB) is a distributed communication framework based on the widely used I2C standard, intended to be used specifically within rapid autonomous robots. Real-time operation guarantees are provided by defining upper bounds in response times. URB facilitates exchange of information between a central controller and distributed sensory and actuator units. Adoption of a centralized topology by connecting distributed units directly to a central controller creates a bottleneck around the central unit, causing problems in scalability, noise and cabling. In order to overcome this problem, URB is physically realized such that gateways (bridges) are incorporated between the central and distributed units which offload the work of the central unit and master the underlying I2C bus. Connection between the central unit and the gateway, the uplink channel, can be established using any high bandwidth communication alternative which successfully satisfies communication requirements of the system. The main contribution of this thesis is the design and implementation of the URB uplink channel using the well known Universal Serial Bus (USB) protocol. Although true real-time operation is not feasible with USB due to its polling mechanism, USB frame scheduling of 1ms is acceptable for our application domain. In this thesis, hardware components used in the USB uplink implementation as well as our software implementation are covered in detail. These details include the firmware running on the gateway, a Linux based device driver and a client control software that uses a USB library running on central controller, and finally sub-protocols between the application-driver and driver-firmware layers. The thesis also includes our experiments to estimate the performance of the USB uplink in terms of its roundtrip latency, bandwidth, scalability, robustness, and reliability. Finally, this thesis also serves as a reference on distributed systems, device driver development, Linux kernel programming, communication protocols, USB and its usage in real-time applications.