11,726 research outputs found
Lightweight Agents, Intelligent Mobile Agent and RPC Schemes: A Comparative Analysis
This paper presents the performance comparison of Lightweight Agents, Single Mobile Intelligent Agents and Remote Procedure Call which are tools for implementing communication in a distributed computing environment. Routing algorithms for each scheme is modeled based on TSP. The performance comparison among the three schemes is based on bandwidth overhead with retransmission, system throughput and system latency. The mathematical model for each performance metric is presented, from which mathematical model is derived for each scheme for comparison. The simulation results show that the LWAs has better performance than the other two schemes in terms of small bandwidth retransmission overhead, high system throughput and low system latency. The Bernoulli random variable is used to model the failure rate of the simulated network which is assumed to have probability of success p = 85% and the probability of failure q = 15%. The network availability is realized by multiplicative pseudorandom number generator during the simulation. The results of simulation are presented
Cross-layer Peer-to-Peer Computing in Mobile Ad Hoc Networks
The future information society is expected to rely heavily on wireless technology. Mobile access to the Internet is steadily gaining ground, and could easily end up exceeding the number of connections from the fixed infrastructure. Picking just one example, ad hoc networking is a new paradigm of wireless communication for mobile devices. Initially, ad hoc networking targeted at military applications as well as stretching the access to the Internet beyond one wireless hop. As a matter of fact, it is now expected to be employed in a variety of civilian applications. For this reason, the issue of how to make these systems working efficiently keeps the ad hoc research community active on topics ranging from wireless technologies to networking and application systems.
In contrast to traditional wire-line and wireless networks, ad hoc networks are expected to operate in an environment in which some or all the nodes are mobile, and might suddenly disappear from, or show up in, the network. The lack of any centralized point, leads to the necessity of distributing application services and responsibilities to all available nodes in the network, making the task of developing and deploying application a hard task, and highlighting the necessity of suitable middleware platforms.
This thesis studies the properties and performance of peer-to-peer overlay management algorithms, employing them as communication layers in data sharing oriented middleware platforms. The work primarily develops from the observation that efficient overlays have to be aware of the physical network topology, in order to reduce (or avoid) negative impacts of application layer traffic on the network functioning. We argue that cross-layer cooperation between overlay management algorithms and the underlying layer-3 status and protocols, represents a viable alternative to engineer effective decentralized communication layers, or eventually re-engineer existing ones to foster the interconnection of ad hoc networks with Internet infrastructures. The presented approach is twofold. Firstly, we present an innovative network stack component that supports, at an OS level, the realization of cross-layer protocol interactions. Secondly, we exploit cross-layering to optimize overlay management algorithms in unstructured, structured, and publish/subscribe platforms
Service-oriented mobility of java code in web services-based architectures
Dissertação apresentada na Faculdade de
Ciências e Tecnologias da Universidade Nova
de Lisboa para a obtenção do Grau de Mestre
em Engenharia InformáticaSoftware mobility consists of providing software components, the ability to migrate to a remote host with the purpose of interacting locally. In other words, this technology enables computations to be transferred from the current machine to a remote one. This powerful enhancement embodied in a traditional network fairly raises security concerns. For now, we believe that software mobility paradigm is confined to environments with bases of trust such as local area networks or middleware layers where security issues can be better controlled.
Service-oriented computations reorganize the network architecture in the form of services, where components are more easily integrated, modified and removed. They have the ability to cooperate between them regardless the programming language used in their development. In addition, service-oriented computing is a widely accepted technology for the implementation of distributed applications, namely middleware.
The work developed in this thesis consists of instantiating a model which combines software mobility and service-oriented paradigms as proposed by Paulino [20]. In this model, migrating sessions take advantage of the resources of a service-oriented network, creating thus an environment where the migration is modeled in terms of services instead of network nodes abstractions.
In the instantiated model, we aim to apply the migration of Java programs in a context of a service-oriented architecture developed with Web services. This application comprises of a middleware layer that runs between the source program and the Web services technologies, and whose interface is the result of the mapping of the operations defined in the model.
The evaluation performed to the instantiated model allows us to identify situations in which component migration to the server to interact locally is more advantageous in comparison to remote interacting with it
Location and routing optimization protocols supporting internet host mobility
PhD ThesisWith the popularity of portable computers and the proliferation of wireless networking
interfaces, there is currently a great deal of interest in providing IP networking
support for host mobility using the Internet as a foundation for wireless
networking. Most proposed solutions depend on a default route through the mobile
host's horne address, which makes for unnecessarily long routes. The major
problem that this gives rise to is that of finding an efficient way of locating and
routing that allows datagrams to be delivered efficiently to moving destinations
whilst limiting costly Internet-wide location updates as much as possible.
Two concepts - "local region" and "patron service" - are introduced based on
the locality features of the host movement and packet traffic patterns. For each
mobile host, the local region is a set of designated subnetworks within which a
mobile host often moves, and the patrons are the hosts from which the majority of
traffic for the mobile host originated. By making use of the hierarchical addressing
and routing structure of Internet, the two concepts are used to confine the effects
of a host moving, so location updates are sent only to a designated host moving
area and to those hosts which are most likely to call again, thus providing nearly
optimal routing for most communication.
The proposed scheme was implemented as an IP extension using a network simulator
and evaluated from a system performance point of view. The results show a
significant reduction in the accumulated communication time along with improved
datagram tunneling, as compared with its extra location overhead. In addition,
a comparison with another scheme shows that our functionality is more effective
both for location update and routing efficiency. The scheme offers improved network
and host scalability by isolating local movement from the rest of the world,
and provides a convenient point at which to perform administration functions
A multi-agent architecture for internet distributed computing system
This thesis presents the developed taxonomy of the agent-based distributed computing systems. Based on this taxonomy, a design, implementation, analysis and distribution protocol of a multi-agent architecture for internet-based distributed computing system was developed. A prototype of the designed architecture was implemented on Spider III using the IBM Aglets software development kit (ASDK 2.0) and the language Java
AGNI: an API for the control of automomous service robots
With the continuum growth of Internet connected devices, the scalability of the
protocols used for communication between them is facing a new set of challenges. In
robotics these communications protocols are an essential element, and must be able to
accomplish with the desired communication.
In a context of a multi-‐‑agent platform, the main types of Internet communication
protocols used in robotics, mission planning and task allocation problems will be
revised. It will be defined how to represent a message and how to cope with their
transport between devices in a distributed environment, reviewing all the layers of the
messaging process.
A review of the ROS platform is also presented with the intent of integrating the
already existing communication protocols with the ServRobot, a mobile autonomous
robot, and the DVA, a distributed autonomous surveillance system. This is done with
the objective of assigning missions to ServRobot in a security context
Models of higher-order, type-safe, distributed computation over autonomous persistent object stores
A remote procedure call (RPC) mechanism permits the calling of procedures in another
address space. RPC is a simple but highly effective mechanism for interprocess communication
and enjoys nowadays a great popularity as a tool for building distributed applications.
This popularity is partly a result of their overall simplicity but also partly a consequence
of more than 20 years of research in transpaxent distribution that have failed to deliver
systems that meet the expectations of real-world application programmers.
During the same 20 years, persistent systems have proved their suitability for building
complex database applications by seamlessly integrating features traditionally found in
database management systems into the programming language itself. Some research. effort
has been invested on distributed persistent systems, but the outcomes commonly suffer
from the same problems found with transparent distribution.
In this thesis I claim that a higher-order persistent RPC is useful for building distributed
persistent applications. The proposed mechanism is: realistic in the sense that it uses
current technology and tolerates partial failures; understandable by application programmers;
and general to support the development of many classes of distributed persistent
applications.
In order to demonstrate the validity of these claims, I propose and have implemented three
models for distributed higher-order computation over autonomous persistent stores. Each
model has successively exposed new problems which have then been overcome by the next
model. Together, the three models provide a general yet simple higher-order persistent
RPC that is able to operate in realistic environments with partial failures.
The real strength of this thesis is the demonstration of realism and simplicity. A higherorder
persistent RPC was not only implemented but also used by programmers without
experience of programming distributed applications. Furthermore, a distributed persistent
application has been built using these models which would not have been feasible with a
traditional (non-persistent) programming language
Heterogeneous Strong Computation Migration
The continuous increase in performance requirements, for both scientific
computation and industry, motivates the need of a powerful computing
infrastructure. The Grid appeared as a solution for inexpensive execution of
heavy applications in a parallel and distributed manner. It allows combining
resources independently of their physical location and architecture to form a
global resource pool available to all grid users. However, grid environments
are highly unstable and unpredictable. Adaptability is a crucial issue in this
context, in order to guarantee an appropriate quality of service to users.
Migration is a technique frequently used for achieving adaptation. The
objective of this report is to survey the problem of strong migration in
heterogeneous environments like the grids', the related implementation issues
and the current solutions.Comment: This is the pre-peer reviewed version of the following article:
Milan\'es, A., Rodriguez, N. and Schulze, B. (2008), State of the art in
heterogeneous strong migration of computations. Concurrency and Computation:
Practice and Experience, 20: 1485-1508, which has been published in final
form at http://onlinelibrary.wiley.com/doi/10.1002/cpe.1287/abstrac
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