Problématique de la mobilité dans les systèmes distribués

nullnull Problématique de la mobilité dans les systèmes distribués Guy Bernard Institut National des Télécommunications, Evry, France Prologue: MotivationPrologue: Motivationhttp://www.tjzgzm.com/ 工矿灯 led投光灯 泛光灯 http://www.u51688.com http://www.qiwhy.comWhat is mobile ??What is mobile ??user mobility terminal mobility user mobility with mobile terminal code mobility network mobility case studies perspectives not considered here: telecommunication infrastructure/services supporting terminal mobility (GSM, WAP, GPRS, UMTS, …) protocols for supporting mobility (Mobile IP, …) database aspects (disconnected transactions, …) adhoc networksUser mobility (1)User mobility (1)problem users are increasingly moving - wish to feel "at home" anywhere office desktop - laptop - home PC - smartphone/PDA - airport - hotel - … need for retrieving one's environment on any machine programs, preferences, data tools and solutions file systems disconnected file systems CODA (Satyanarayanan, CMU, 1990), Ficus (Popek, UCLA, 1990), Bayou (Petersen, Xerox, 1995) automatic hoarding (Popek, UCLA, 1997) using a smart card as a portable computer/data repository RNRT "CESURE" project (Gemplus - INRIA Grenoble - LIFL - INT) example: tele-meeting Grenoble University campus project (pool of non-personal desktops) user preferences / accountingParenthesis: smart card capabilitiesParenthesis: smart card capabilitiesthe smart card IS a real computer processor, memory, custom OS JVM - Javacard 2.2 current generation: 128K ROM, 64K EEPROM, 4K RAM acts as a slave (server) answering requests from the (client) host terminal prototypes Gemplus, 1999: 2 MB of memory Gemplus, 2001: 224 MB of memory keyboard, screen software: SC can be active in the SC -- host terminal interactions for SC manufacturers, the tomorrow's computer is the SC Smart phones are just a SC plus a keyboard, a screen and an antenna for SP manufacturers, the tomorrow's computer is the SP SC is just used for persistent storage and authentificationUser mobility (2)User mobility (2)corollary 1: handling heterogeneity processors, OSes HMI screen size - keyboard - pointer - mouse - voice command … current solution component-based distributed software clear separation of application engine and application HMI dynamic loading of appropriate HMI component example: RNRT "CESURE" project: "intelligent" tradingUser mobility (3)User mobility (3)corollary 2: very large scale systems world-wide services (naming, location, …) robust and scalable algorithms (IP routing, DNS, …) example GLOBE project (Tanenbaum, VU Amsterdam, 1996) large scale load balancing between distributed servers current algorithms are not scalable synchronous communications, centralized load balancers suited for a large number of hosts on a high speed / short range network - eg., AOL Web cache (> 1,000 nodes) - MSN Hotmail (> 5,000 nodes) need for decentralized / asynchronous algorithms example: OMG's Load balancing and Monitoring RFP, document orbos/2000-04-27 co-author of the joint accepted answer (Tri-Pacific Software - VERTEL - IONA - Alcatel - INT - Lucent Tech. - PrismTech - UC Irvine - Univ. Toronto), june 2002 (document orbos/2002-04-05) open problem: large scale copy consistency for modifying access patternsUser mobility (4)User mobility (4)corollary 3: location-dependent data added-value services (weather forecast, restaurants, taxis, …) solution: extend trading service for static terminals, the geographical position is known if (l1 location determination must be dynamic requires a support from telecom provider / GPS / … survey of location systems for ubiquitous computing: IEEE Computer, August 2001 GPS 24+3 satellites - accuracy: 1-5m (95-99%) - not indoor E911 US Federal Communications Commission initiative wireless phone providers must develop a way to locate any phone that makes a 911 emergency call many companies are developing a variety of location systems to determine a cellular phone's location these systems will also support new consumer services (find the nearest gas station, post office, or automated teller machine)User mobility with mobile terminal (2)User mobility with mobile terminal (2)a lot of applications eg., guiding firemen, or search-and-rescue team for the best route to quickly locate all the avalanche victims) tentative solution: trader federation a lot of opened problems, eg. where are the traders located? how do they cooperate? how many traders? how does the terminal knows where are the traders? ...Code mobilityCode mobilityreferenced code RPC, RMI, HTTP/CGI - synchronous remote evaluation Java servlets - synchronous - code is pushed on-demand code Java applets - asynchronous - code is pulled mobile code (mobile agents) code and state move together - asynchronous neither "push" nor "pull" model - rather, self mobility (proactive migration) ...instruction i ; go ("somewhere") ; instruction i + 1 ; ... a network connection is needed only during agent transfer between sites survey of mobile code system-related problems: Fuggetta et al., 1998 fits well with wireless terminals and terminal mobility application code can jump from a nearby server to current user location is proactive migration (mobile agents) really needed??Network mobilityNetwork mobilityconstellations of LEO satellites (eg., Teledesic) viewed by satellites, even mobile users are almost still dual problem of mobile users within a network of static servers if satellites embed applicative code, this code moves over users code jumping to user terminals when seen by a satellite?? no outstanding research work in this area Case studiesCase studieshandling user mobility CESURE application-aware adaptation to bandwidth variability ODYSSEY to network disconnections ROVER DOMUser mobility: RNRT CESURE ProjectUser mobility: RNRT CESURE ProjectModelling and exploitation of the concept of service application to mobile users of the network Service application distributed application providind an added-value service to users Mobile users users can connect to the service from anywhere, any kind of terminal (including mobile terminals: smart phones, PDAs, …) november 1999 - november 2001 Gemplus - INRIA Grenoble - LIFL Lille - INT funded by Ministry of Research CESURE: problemCESURE: problemNomadic userServiceCESURE: ObjectivesCESURE: Objectivesprovide tools and system infrastructure for mobile applications enabling building added-value services creating dynamically instances of applications adapted to the user architecture based on 2 types of elements downloadable and configurable components remote services  Based on a smart card acting as a central point for the applicationCESURE: mobile / configurable componentsCESURE: mobile / configurable componentsno standard definition, but… autonomous software module that can be installed on different platforms exports several attributes, properties or methods can be configured benefit being configurable building block enabling to build applications by compositionCESURE: Software architecture descriptionCESURE: Software architecture description2 steps the designer specifies the architecture using an Architecture Description Language the architecture is then "deployed" system service for deployment and executionconsultcharacteristicsComponent databaseCESURE: ApproachCESURE: Approachapplication design according to a modular approach (distributed sofware components)application description in a smart carddeployment and execution platform for instantiating the configuration the best suited to the contextCESURE: Component-based applicationCESURE: Component-based applicationexample application: weather forecast available anywhere, from any terminal type the user gets weather forecast: relative to his/her current location according to service subscription options (3 days, terrestrial, in french) adaptation requirements: the application configuration must be adapted to the terminal (HMI, processor/network characteristics, …) to the current user location to subscription parameters to the state of the environment (load of servers, ...)CESURE: Application layout CESURE: Application layout WeatherServer provides raw forecast data WeatherConsult receives raw forecast data and adapts them according to subsrciption parameters UserInterface displays the data according to terminal typeForecastDisplay InterfaceForecastData InterfaceUserInterfaceWeatherConsultWeatherServerusesusesprovidesprovidesruninitinitCESURE: Component descriptionCESURE: Component description More information has to be associated to components -- eg, some description of provided functionality Application descriptionApplication description Application deployment - Installation scriptApplication deployment - Installation scriptdefault_directory = "dir.meteo.com:3000" params.directory = default_directory // looking for existing components meteo = locate_component ( params, "WeatherServer" ) // instanciation of new components -- local or remote params.host = 'localhost' hmi = create_component ( params, "UserInterface" ) params.host = 'any' client = create_component ( params, "WeatherConsult" ) // component connexion connect ( BASIC, client.display, hmi.display ) connect ( BASIC, client.data, meteo.data) // service customization client.init () // application starting hmi.run () NB - this is a generic logical description of the application -- some params (eg, terminal type, will be determined at deployment time)CESURE: Deployment platformCESURE: Deployment platformReconfiguration servicesCESURE: Extended trading serviceCESURE: Extended trading serviceDeployment EngineInstance ManagerExecution servers Package librariesCESURE: "Intelligent" extended tradingCESURE: "Intelligent" extended tradingHost is known - package lookup: reasons GUI component  host = user terminal co-location of components search the apropriate package that can be instantiated on the given host Criteria: OS, runtime, available software, display capabilities Package is known - host lookup: Find an host that can instantiate the given package Criteria : OS, runtime, required software If several host are suitable, select the least loaded one for package instantiation Instance lookup: If several instances are already installed, select the one running on the least loaded one CESURE: Monitoring InfrastructureCESURE: Monitoring InfrastructureCollecting load information in the Linux kernel DLBARuntime processus CPU utilization machine availability = CPU capacity / number of active threads CPU capacity quantified in “bogomips” (Linux unit) Memory utilization Monitoring information spreading HostLoadUpdater processus UDP datagrams (CDR encoding) sent only in case of significative changes in load state CESURE: Deployment of a sample applicationCESURE: Deployment of a sample applicationGUIAutomatic transfer agentBNPServerBNP accountLaPosteServerpre-instantiated componentLaPoste accountBanking application CESURE: Deployment stepsCESURE: Deployment stepsBank accountsTrader5) search for a Transfer Agent package1) send terminal properties2) search for bank accounts3) search for interface package6) search for the less loaded serverpackagesTransfer Agent 7) instantiation of Transfer AgentCESURE: Demo application prototypeCESURE: Demo application prototypeinterfacing a monitoring tool with a trading service prototype 3 laptops 2 PCs under Linux JDK 1.3 + ORBacus 1 PC under Windows 2000 JDK 1.3 (contains Swing) + ORBacus 1 iPAQ WinCE + J9 (contains MicroView) + OBE (ORBacus Embedded Java) Network 802.11b 11mbit/s wireless Ethernet CESURE: Demo application prototypeCESURE: Demo application prototypeterminalWindows CE Ipaq (ipaq1)CESURE: Application interface for iPAQCESURE: Application interface for iPAQCESURE: Application interface for PCCESURE: Application interface for PCCESURE: Demo application trader consoleCESURE: Demo application trader consoleCESURE: evaluationCESURE: evaluationmain contribution provide a generic architecture for the deploy