Communication strategies for distributed embedded systems

1. Communication strategies for distributed embedded systems

2. Table of contents • Jini • Java Embedded Server • CORBA for Embedded Systems

3. Jini technology

4. Table of Contents for Jini • What is Jini? Why Jini? • Features • Architecture • Example • Advantage • Disadvantage • Comparison with other technology • Conclusion

5. What is Jini? • Jini technology promises to be a reality in the immediate future as an architecture to enable connections between devices any time, anywhere

6. Devices • Printers • Storage devices such as disks • Personal digital assistants • Digital cameras • Cell phones • Residential gateways • Digital video cassette recorders • TV sets, DVD players • Industrial controls, and every sort of imaginable consumer electronics device.

7. Why Jini technology? • Today devices are unaware of their surroundings • They are rigid and they can not adapt • We expend a lot of efforts to install it • We need an expert to do it for us

8. Scenario • Just before bed, the man with the laptop reads his email, half-watching the local news. The anchor mentions a brief piece on the local zoo's Panda. His daughter is doing a project on it, so he records the piece on his laptop's drive. Just before bed, he decides to email it to her as a surprise.

9. Features • Jini[TM] connection technology is based on a simple concept. • Devices should work together. • They should simply connect. • No drivers to find • No operating system issues • No weird cables and connectors

10. Architecture

11. Instant On • When we plug a Jini technology-enabled device into the network, it works. Right away. No fuss. • Its services and resources are immediately available.

12. Special delivery •   Jini technology services are available on demand, whenever they are needed. • Impromptucommunity • A community put together without any planning, installation, or human intervention.

13. Impromptu community • Jini software lets all devices work together, so we can create our own personal network or community--any time, anywhere. • Connect our home appliances so we can control them centrally. • Connect our office equipment so people can share resources. • Interact with other Jini communities quickly and easily.

14. Resilient • Jini technology communities adapt very quickly to changes • Users come and go, the community lives on. • Jini community is always available, while the Service Age allows the systems to be more tolerant and redundant

15. Historical trends • Three dimensions of improvements • Size, cost, and computational power • Mainframe: a company • Mini: a department • Work stations: a group • Microcomputer: personal • Web • Community

16. Jini connection technology requires a few things • an infrastructure which operates as a dynamically distributed system • a common language and implementation that enables low-overhead communication between distributed objects • a lookup service (which identifies objects that supply those services) • an add-in protocol which is implemented on each device--we call this the discovery/join protocol • a subtract-out mechanism--providing resilience when a device is unplugged--which is called leasing

17. Services • The most important concept within the Jini connection architecture is that of a service. • A service is an entity that can be used by a person, a program, or another service. • A service may be a computation, storage, a communication channel to another user, a software filter, a hardware device, or another user.

18. Services • Services may make use of other services, and a client of one service may itself be a service with clients of its own. • Services to be added or withdrawn from a federation at any time according to demand, need, or the changing requirements of the workgroup using it.

19. Look up server Operation • Services are found and resolved by a lookup server. • The lookup server is the central bootstrapping mechanism for the system • It provides the major point of contact between the system and users of the system.

20. Discovery and Join • A service is added to a lookup service by a pair of protocols called discovery and join. • First, the service locates an appropriate lookup server, using the discovery protocol • Secondly, it joins it using the join protocol. • When a service joins a lookup server, a service object for that service is loaded into the lookup server.

21. Interfaces • The client interacts with a service via a set of interfaces written in the Java programming language. • These interfaces define the set of methods that can be used to interact with the service. • Programmatic interfaces are identified by the type system of the Java programming language

22. How user interface works? • Services can be found in a lookup service by asking for those that support a particular interface. • this way ensures that the program looking for the service will know how to use that service • A user interface can also be stored in the lookup service as an attribute of a registered service. • A user interface stored in the lookup server is an implementation that allows the service to be directly manipulated by a user of the system.

23. How Jini works? (Process) • To use a service, a person or a program locates the service using the lookup service. • The service's interface is copied from the lookup service to the requesting device where it will be used. • The lookup service acts as a switchboard to connect a client looking for a service with that service. • Once the connection is made, the lookup service is not involved in any of the resulting interactions between that client and that service.

24. Main Challenges • Defining and perfecting the underlying protocols and infrastructure • TCP/IP, HTTP, SMTP and FTP protocols and their implementations • Creating applications and services on the top that infrastructure • email composers and readers, file fetching programs, Web browsers, and the Web stuff

25. Underlying Technology • Jini connection architecture is only what is needed to gather a group of devices into an impromptu community that is simply connected • A simple protocol to discover a lookup service and join it, a lookup service which acts as a switchboard connecting clients to services, • The Java programming language to provide the underlying object model, • RMI technology to provide federation and to move objects.

26. Details of Architecture

27. An Example

28. Advantages • We no longer need a computer to act as an intermediary between a cell phone and a printer • These devices can take care of themselves-they are flexible, they adapt • Self configure • Self diagnose • Self install • Reduce need for expert help • Lower total cost

29. Disadvantages • Communication overhead, so some time it’s slow • High Learning curve and some cost involve

30. Comparisons with other similar technology • Bluetooth is a technology specification for low-cost, short range radio links between laptops, mobile phones, and other portable devices. When two Bluetooth devices come close together, they automatically detect each other and establish a network connection. • Motorola's Piano, which can be built on top of Bluetooth, specifies what sort of information they exchange and how they communicate.

31. Comparisons with other similar technology • Hewlett Packard's JetSend technology is an example of a service protocol that allows devices like printers, digital cameras, and PCs to intelligently negotiate information exchange--without user intervention. • HAVi (Home Audio-Video interoperability) is a specification for home networks of consumer electronics devices such as CD players, televisions, VCRs, digital cameras, and set top boxes.

32. Conclusion • by looking to simple devices as the archetype of how to design devices and • by creating a way to simply connect them, • We may at last begin to see advanced computer technology simplify our lives.

33. References for Jini • 1.      “Jini home page on Sun microsystem web site”, http://www.sun.com/jini/ • 2.      “Jini™ Connection Technology Fact Sheet”,http://www.sun.com/jini/factsheet/ • 3.      “Why Jini Technology Now?” http://www.sun.com/jini/whitepapers/whyjininow.html • 4.      “Jini™ Technology and Emerging Network Technologies”http://www.sun.com/jini/whitepapers/technologies.html • 5.      “Jini™ Technology and the Java Dynamic Management™ Kit Demonstration” http://www.sun.com/software/java-dynamic/wp-jdmk.kit/ • 6.      “Jini specifications”, http://www.sun.com/jini/spec • 7.      W. Keith Edwards, “Core JINI”, Sun Microsystems Press 1999

34. Embedded Java Server

35. Java Embedded Server • Java Embedded Server allows remote devices to upload, download, activate, and deploycustomized services and applications precisely when they are needed. • These services can also be automatically removed from the device when their use is completed, freeing memory. • the ability to monitor a device, perform diagnostic evaluations, set up remote administration and more.

36. Why Java Embedded server? • Today's rapid increase in the intelligence of devices presents a unique opportunity for the enterprise to extend applications beyond the desktop. • Gas pumps, vending machines, energy meters, or ATMs that once stood alone can now easily be connected to the enterprise network.

37. Why Java Embedded server? • Sun introduces the Java Embedded Server™ product, a small application server designed to be embedded in remote devices. • Using the Java Embedded Server product, you can respond to changing market requirements by installing and managing new software and services on your devices over the network-dynamically, securely, and just in time.

38. Challenges for Providing Services to Embedded Devices • The challenge behind the opportunity is to provide services to these embedded devices in a way that matches the dynamics, simplicity, and ubiquity of the Internet. • The way to do this is to provide consistent reliable mechanisms for service providers to develop, deliver, and support "just-in-time" services to these devices. Services will need to be: • available on demand • upgraded dynamically • remotely managed • secure

39. Solution with java Embedded server • By using the Java™ Embedded Server™ with the Internet, services can be delivered, upgraded, and managed as they are needed and then fade off into the ether when they are not in use. • One example of this might be a Rolodex service that gets loaded into a hand-held device or television as it is needed, but when it is no longer in use, its context is saved and the service is pushed back to a server.

40. Features and benefits • Communicate with remote devices and equipment deployed in the field • Extend the useful life of devices by dynamically adding features and functionality, on demand • Create Jini™ technology Federations for device-to-device communications by hosting "registry" and "look-up" services for Jini technology • Leverage the portability, reusability, and productivity of the Java™ programming environment

41. Architecture of Java Embedded Server

42. System architecture • Java Embedded Server consists of two primary components: the ServiceSpace and the Services. • The ServiceSpace, only 100KB in size, provides a runtime framework that manages the loading, installation, activation, execution, and removal of applications, called services. • The Services are a set of useful pre-built and customizable services. • The Services include a set of pre-packaged application services, including a lightweight HTTP server, an SNMP agent, a scheduling service, and a Servlet manager. • Device providers and developers can build their own services using the Java Service Designer tool.

43. System Architecture • Device providers and developers can build their own services using the Java Service Designer tool. • The ServiceSpace is installed on a device running an embedded operating system. • ServiceSpace requires a Java runtime platform, such as EmbeddedJava, PersonalJava, or the standard JDK. • The services can be stored anywhere on the network, and they are downloaded and executed as required.

44. Application Service Bundles • An application service is deployed using an application service bundle. • A bundle comprises a Java archive (JAR) file and a set of instructions for the Java Embedded Server. • The instructions come in the form of Java objects called wizards.

45. Each bundle contains the following: • Manifest. The manifest defines the contents of the bundle. • Installer Wizard. The installer wizard installs the service on the server. • Activator Wizard. The activator wizard starts the service and registers it with the server. • Update Wizard. The update wizard automatically manages version control and replaces older versions of the service with the latest one. • Dependencies Wizard. The dependencies wizard identifies any dependencies this service may have on other services and determines if the services are available. • Content. The content contains Java classes and other files used by the service.

46. Example: Create Versatile Gateway Solutions • A gateway links devices in local networks in the home or small office to the Internet and external service providers. • These gateways create a focal point for enterprises and service providers to deliver services to client devices internal to the gateway. • Java Embedded Server technology is an ideal solution for powering low-cost and zero main-tenance gateways that need to be remotely configured, upgraded, and managed.

47. Java Embedded Server in Application: Versatile Gateway

48. Enable "Zero Latency" Enterprises • By connecting remote devices to enterprise applications, Java Embedded Server technology enables enterprise applications to instantly respond to all enterprise-wide supply chain events and deploy customized and value-added services to these devices, on demand. Usage scenarios: • A vending machine, linked to the enterprise supply chain, can transmit consumption data and automatically re-order replacement supplies • A gasoline pump becomes a dynamic platform capable of delivering targeted promotions to the customer • Routers (or copiers) can be remotely diagnosed and repaired

49. Java Embedded Server VS Jini • By using the Java™ Embedded Server™, services can be delivered, upgraded, and managed as they are needed • The Java Embedded Server allows a device to dynamically download and execute an application from a remote location on the network. • Jini provides a loosely coupled mechanism for applications on different devices to communicate and share services. • Jini doesn't provide a mechanism to dynamically load application services within a device. • Java Embedded Server could provide a mechanism to dynamically load Jini services. • The two technologies are complementary.

50. Personal Java VS Embedded java • There are two primary subsets of Java that have been endorsed by the industry: • Personal Java (shortened as pJava) • Embedded Java (eJava). • Both of these are small-footprint versions of full-blown Java. • they run the same bytecodes and have exactly the same language semantics as full-blown Java, • they have significantly reduced sets of class libraries available to them.