Interaction model of grid services in mobile grid environment Ladislav Pesicka University of West Bohemia

The main topics Using mobile devices –To access computation grid –To be a part of the grid Support of mobile agents –Disconnected computing –Migration

Content Computation grids –short overview Mobile devices –restrictions The role of mobile agents –how to help –Interaction model

Grids In mid. 1990s, most development in last years –> web services, XML Distributed computing infrastructure for advanced science and engineering Establish virtual organizations (VO) Manage security, trust, privacy Manage and monitor distributed resources

Virtual Organization (VO) Real organizations can participate in one or more VO Resource sharing – conditional (constraint given by resource owner) when, where and what can be done Member services what resources able to access, the quality, and the policies that govern access

Standards OGSA (Open Grid Service Architecture) defines what Grid services are, no technical and detailed specifications OGSI (Open Grid Service Infrastructure) formal and technical specification Globus Toolkit 3 ( implementation of OGSI

Open Grid Services Infrastructure (OGSI) OGSI defines mechanisms for creating, managing, and exchanging information among entities called Grid services Grid service - a Web service that conforms to a set of conventions (interfaces and behaviors) that define how a client interacts with a Grid service

Grid service Grid service factories concept responsible for creating and destroying of objects Client performs operations on the same instance of Gs One instance – used mostly by one client Service data elements – state of the service Factory: -Create instance -Destroy instance

Grid service – naming Distinguish among different instances GSH (Grid Service Handler) - naming, URI CounterFactoryService/hash GSR (Grid Service Reference) in the form of WSDL document describes what the clients need to know to be able to communicate with grid service

Globus Toolkit 3 Grid service middleware Implementation of core grid services based on OGSI – pure Java language, other services in C language Important services: –GRAM (Globus Resource Allocation Manager) –GridFTP (File Transfer Protocol, similar to FTP) –MDS3 (Monitoring and Discovery Service) –GSI (Grid Security Infrastructure)

Grid - resources Provides list of available resources together with its characteristics These characteristics are given by available SDE (Service Data Elements), just its values can change - predefined

RSL (Resource Specification Language) In the form of pair (Atribute, value) Resource metric or configuration parameter Used to specify requirements of the application Executable, directory, stdin, stdout, … Globusrun –r node –o &(executable=/bin/ls)

Resource allocation Deep knowledge of –Client demands (computational and memory allocation demands) –Offer of given resource (speed, available memory) Work with incomplete knowledge missing or just estimated information (computation power vs. supposed lifetime) Do not know requirements of future clients

Mobile devices - restrictions Host resources (computation capability, memory, limited power sources) Network resources (narrow bandwidth, latency, lost of signal, costs) Security issues (security problems in wireless networks) Interoperability (different OS, HW and SW equipment) Availability (power-loss, switching off initiated by the user)

Mobile agent support To obtain resource characteristics (need to gain more information then SDEs) To control the computation instead of mobile device (support for disconnected computing) Perform some actions on the mobile device (computation, searching) (MD as computation resource)

System architecture Home network, Foreign network Grid environment – VO Home base inside Home network MA hosting environment available in resource nodes of the foreign network Stationary agent in MD – control communication with home base

Home base One node in the home network (optionally visitors base in foreign network) More nodes can be home base candidates (against the failure), communicate together to know which one servers the given mobile device Mobile device – a priority list of IPs, or DNS names of the candidates

Home base Main tasks: –Repository of agents owned by the users that could be sent to the network –Agent management system –Messages queue to collect notices and logs for the client (MD), at the time it is disconnected

The model of interactions Home network Foreign network 1,4 2 3 Mobile device (dynamic IP) Home base (static IP) The choice of most suitable resource 1 request, 2 MA sent, 3 MA returns, 4 response

Control of the computation based on MA Client sends request to the home base Home base – agents repository, including: –Agents to find proper resource node –Agents capable to control comp. on the foreign node (where they will be sent) Feedback – agent communicates with home base or directly with mobile node Using certificates (VO agreement)

MD as computation resource Mobile device as grid-enabled node Mobile device includes environment to host mobile agents Lifetime management (power down) Accounting – e.g. communication costs (WiFi connection) in foreign network can be paid in the form of computational cycles (powerful notebooks)

Some problems and features Availability of suitable J2ME (or J2SE) environment for different kind of mobile devices Availability and stability of mobile agents hosting environment for the mobile devices Take care about robustness, security, communication overhead of the system

Conclusion Mobile devices –Demand for mobile access to the grids –They are more and more powerful (source of information, computation cycles) Mobile agents –Agent based grid –Monitoring of grids Mobile grids –As energy outlets – just connected and obtain proper computation power and resources anywhere anytime

Thank You for Your Attention