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Jini TM Architecture

Jini TM Architecture. Source : Sun Microsystems Inc., Jini TM Architecture Specification; www.sun.com/jini/specs/jini1_2.pdf Jini TM – A Technology for interconnecting heterogeneous devices; Lauri Eronen University of Helsinki, Department of Computer Science

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Jini TM Architecture

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  1. JiniTM Architecture Source : Sun Microsystems Inc., JiniTM Architecture Specification; www.sun.com/jini/specs/jini1_2.pdf JiniTM – A Technology for interconnecting heterogeneous devices; Lauri Eronen University of Helsinki, Department of Computer Science California Software Laboratories, Jini by example - Whitepaper; www.cswl.com/whitepaper/tutorials/jini.html Sun Microsystems Inc., JiniTM Connection Technology Architecture Overview by Bill Day Presented by Mark Miyashita 04-08-2002

  2. Topics • Who developed Jini? • Why Jini? • What are the Goals, benefits, and Limitations? • What is Jini? • Jini Architecture Overview • Related technology

  3. Who developed Jini? • Jim Waldo (COBRA, RMI, JavaSpaces) • Bill Joy (BSD Unix, SunOS) • Ken Arnold (JavaSpaces) • Bob Sheifler (X Window Systems) • In addition, many developers and partners involved in developing and assist in maturing Jini technology

  4. Why Jini? • Distributed computing is more difficult than local computing because of: • Network Latency • Concurrency issues • Memory Management • Inevitable partial failure

  5. Goals of Jini • Enabling users to share services and resources over a network • Providing users easy access to resources anywhere on the network while allowing the network location of the user to change • Simplifying the task of building, maintaining, and altering a network of devices, software, and users

  6. Benefits (value) of Jini • Makes using a network more like using a phone (plugging in networked devices and application software is as simple as plugging in a phone) • Simplifies adding and management of application services easier • Simplifies the task of writing distributed application by freeing programmers from worrying about underlying network topology

  7. Limitations of Jini • Scalability – intended for less than 1,000 resources • Requires Java 2 Platform, 48KB of memory – Jini’s Java-dependency, require too much processing power and memory for most devices (new Jini device architecture Specification address this issue) • Many standardized interfaces for Jini services are under development (Jini Printer Working group, Jini Storage Working Group, see www.jini.org)

  8. What is Jini Technology? • An infrastructure to federate services in a distributed system • Jini enables spontaneous networks of software services and devices to assemble into working groups of objects, or federation • Simplify delivery and access of network services • Jini addresses the problem of distributed computing using a set of simple interfaces and protocols

  9. What is Jini Technology? • Adapting to the changing nature of the network and mobility of devices and services • Jini provides simple mechanisms which enables devices and services to be removed/added to the federation • Everything is represented by Java objects • Everything is located and accessed through Java interfaces

  10. Key Concepts • Services • Lookup Services • Discovery and Join protocols • Java Remote Method Invocation (RMI) • Security • Leasing • Transaction • Distributed Events

  11. Jini Architecture Overview Jini Service Application Service Lookup Jini infrastructure Discovery/Join RMI Operating System Network Transport • Java VM and RMI is the basis for Jini infrastructure. • Java VM and portable object code provides benefit of homogeneous network and architecture independence

  12. Components of a Jini System • Jini extends the Java Platform • Divided into three categories: • Infrastructure – set of components that enables building a federated Jini system (defines the minimal Jini code) • Services – actual services constructed using Jini (entities within the federation) • Programming Model – set of interfaces that enables the construction of reliable services including the services belonging as part of the infrastructure as well as actual services

  13. Components of a Jini System

  14. Jini Infrastructure – Jini Lookup Service • Repository of available services • Stores each service as Java objects • Clients download services on demand • Lookup service provides mapping: interfaces to objects • Lookup service may include entry for other lookup services (federated with other lookup services) • Lookup service interface provides: registration, access, search, removal

  15. Jini Infrastructure – Jini Lookup Service • In short, Jini Lookup service is about finding service in the federation by the client • To find a service, a Jini client locates appropriate service by querying a lookup service by type (Java interface) • Code moves from service to client via lookup service • Code needed to use service is dynamically loaded into client on demand

  16. Jini Infrastructure – Discovery/Join protocol • Discovery and join occur when device is plugged in (pair of protocol used to find and join a group of services) • Discovery occurs when a service provider is looking for a lookup service with which to register • Join occurs when a service has located a lookup service and wishes to join it • Jini discovery/join is the process of adding a service to a Jini system

  17. Jini Infrastructure – Discovery/Join protocol • A service provider is the originator of the service – software or hardware • Based on UDP multicast – service provider locates a lookup service by multicasting a request on the local network for any lookup services • Provide required software drivers and its capabilities – service object (proxy) for the service is loaded into the lookup service • Service object (proxy) contains the Java programming language interface for the service, including the methods that users and application will invoke to execute the service

  18. Jini Infrastructure – Discovery/Join protocol • Along with service objects, descriptive service attributes (service capability) gets loaded into lookup service during the join phase • In short, discovery/join protocol establish references with lookup service • Unicast discovery also supported

  19. Jini Infrastructure – Java RMI • Java Remote Method Invocation (RMI) mechanism is a fundamental for Jini • RMI is an Java language based extension to traditional remote procedure call mechanism • Passing both remote object references (pass-by-reference) and actual object (pass-by-value) as method parameters are possible • RMI allows not only data to be passed from object to object around network but also, full objects including executable code to be move around in a network

  20. Jini Infrastructure – Java RMI • Communication among services uses Java RMI • RMI provides • Activation – Java objects that provides services need not be running all the time (it can be activated by RMI when a request for the service arrives) • garbage collection • multicast

  21. Jini Infrastructure – Distributed Security • A distributed security system that extends the basic Java security model (JVM protects the client from malicious downloaded code that could cause damage) • Principal – Jini services are accessed on behalf of some entity which generally traces back to a particular user of the system • Access control list – Associates access privileges with each object implementing a service (service may request access to other service based on the identity of the object that implements the service)

  22. Jini Infrastructure – Discovery protocol UDP Multicast Service provider seeks LUS

  23. Jini Infrastructure – Join protocol A service provider registers a service object (proxy) and its service attributes with the lookup service (joins a federation) for other clients and services to use

  24. Jini Infrastructure – Lookup Service Client Requests a service by type (java interfaces) and/or service attributes. A copy of the service object is moved to the client to talk to the service provider Service Provider

  25. Jini Infrastructure – Using Service • All communication happens between the client and the service through service object (proxy) • Independent of wire protocol – the method of communication between the client and the service is not specified in the Jini architecture • The actual communication method is determined by the service provider, who provides service object (proxy) that implements that interface • Protocol can change without affecting client • RMI semantics is core to functionality – it can use any other communication method

  26. Jini Infrastructure – Using Service • The client interacts directly with the service provider via the service object (proxy) • Lookup service is no longer involved Service Provider

  27. Example – Jini Enabled Printer GUI Drivers Jini Infrastructure Java VM

  28. Example – Discovery Multicast query for Lookup service UDP Multicast

  29. Example – Discovery Lookup service discovered LUS

  30. Example – Join Printer registers service object (proxy) with LUS LUS

  31. Example – Lookup Client search LUS for Printer Printer ? LUS

  32. Example – Lookup LUS returns printer service to client LUS

  33. Example – Using services Client communicates to printer through service object (any protocol) LUS

  34. Programming Model – distributed leasing • Problem : Partial failure in distributed systems can lead to unchecked resource consumption • An access to services in Jini is lease based • A lease is a grant of access over a time period (protocol for managing resources using a renewable, duration based model) • Each lease is negotiated (contracted) between the user of the service and the provider as part of this protocol • Leases are either exclusive or non-exclusive (service can not be shared)

  35. Programming Model – distributed leasing • If lease expires without renewal, user and provider can free up associated resources • Leases handle client and network failure, removal of services (leases may be cancelled, renewed, allowed to expire) • Resources are allocated only as long as continued interest is shown by leasee (leasee’s responsibility to renew lease before expires) • Used also in LUS to keep the list of available service up to date (service provider must renew the lease) • In short, lease provides a method of managing resources in a environment where failure can occur

  36. Programming Model – distributed Events • Jini extends standard Java event mechanism to work in a distributed network • Register interest, receive notification (an object may allow other object to register interest in the object and receive a notification of the occurrence of such an event • Use RMI and distributed leasing protocol • In LUS, delivering to the LUS information about state changes of services registered to the LUS

  37. Programming model – Transaction • Jini includes interfaces that define the functionality needed for performing a two-phase commit (Jini specification does not dictate the semantics for the concept of transaction, only interfaces are provided) • Transaction interface introduce a lightweight, object oriented protocol enabling applications to coordinate state changes (designed for distributed object coordination)

  38. Services • Infrastructure and programming model are built to enable services to be offered and found in network federation • Service may be added or removed from a federation at any time • Provides mechanism for service registration, lookup, and use • Services represented (defined) by Java interfaces – implementation can change over time without effecting infrastructure or clients

  39. Services are defined by Java interfaces I’m a printer Interface printer I’m a color printer Interface Color Printer

  40. Client finds service by interface Give me a Printer Client LUS Interface printer Interface Color printer

  41. Jini and CORBRA/DCOM • Jini • Java technology centric • Code movement during runtime • COBRA/DCOM • Cross language support • No code movement • Integration • COBRA/DCOM components can be wrapped as Jini services

  42. Jini and UPnP • Jini • Code movement during runtime • Service centric • UPnP • No code movement • Device centric • Integration • UPnP devices can be wrapped as Jini services

  43. Jini and Bluetooth • Bluetooth • Open standard for wireless proximity networking communication • Based on low cost, short range radio link • Ad-hoc connection among mobile devices • Jini and Bluetooth • For IP-based Bluetooth devices, Jini should work without modifications • For non-IP-based Bluetooth devices, proxy-based Jini services can be built

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