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

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Jini technology
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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

• JiniTM 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

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Architecture
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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.
• Impromptu community
• A community put together without any planning,
  installation, or human intervention.

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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.

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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

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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

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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

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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.

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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.

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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.

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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.

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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

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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.

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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.

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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

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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.

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Details of Architecture
27
An Example
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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

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Disadvantages

• Communication overhead, so some time its slow
• High Learning curve and some cost involve

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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.

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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.

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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.

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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.htm
  l
• 4.      Jini Technology and Emerging Network
  Technologies http//www.sun.com/jini/whitepaper
  s/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
•  
•  

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Embedded Java Server
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Java Embedded Server

• Java Embedded Server allows remote devices to
  upload, download, activate, and deploy customized
  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.

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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.

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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.

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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

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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.

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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

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Architecture of Java Embedded Server
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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.

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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.

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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.

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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.

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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.

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Java Embedded Server in Application Versatile
Gateway
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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

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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.

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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.

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Personal Java VS Embedded java

• Personal Java is largely intended for
  programmable devices that have interfaces on them
  -- devices such as cell phones and PDAs
• These devices are usually able to download applet
  code and have at least AWT and sometimes the Java
  Foundation Classes available for user interfaces.
  
• The main things missing from pJava are the
  "enterprise"-oriented APIs database
  connectivity, CORBA communications, and
  (sometimes) RMI.
• pJava devices that are intended to work with Jini
  will almost certainly support RMI.

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Personal Java VS Embedded java

• For Embedded Java devices, the situation is
  somewhat more restricted.
• eJava devices are less likely to be found in the
  Jini context.
• Embedded Java is a more limited subset of Java
  and Personal Java -- it makes most of the user
  interfaces classes optional, along with most of
  the networking classes
• an eJava device can participate in Jini if
  another piece of software is working on its
  behalf to make it visible through Jini.

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References for java embedded server

• http//www.sun.com/software/embeddedserver/
• http//www.sun.com/software/embeddedserver/whitepa
  pers/whitepaper2.html
• http//www.sun.com/software/embeddedserver/whitepa
  pers/whitepaper1.html

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CORBA for embedded Systems
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Common Object Request Broker Architecture (CORBA)
for Embedded Systems

• Object management group(OMG) is preparing
  proposals for a stripped-down version of CORBA
• could be used in embedded computer systems to
  enable developers to more easily define
  communications between components and to
  incorporate reusable objects.
• The Common Object Request Broker Architecture
  extensions would provide developers with a common
  interface to connect components within embedded
  systems in household appliances, cellular phones,
  cars and airplanes

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CORBA for Embedded Systems

• The interface will allow users to build reusable
  objects and to make writing, debugging and
  maintaining applications easier
• To work in embedded systems, which have very
  little memory, CORBA will have to be stripped
  down to its essence,
• A minimal CORBA, however, would still support
  multiple languages and interface easily with
  remote objects through an ORB (object request
  broker).

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CORBA for Embedded Systems

• The standards also would have to be compatible
  with existing versions of CORBA.
• An ORB based on the proposed standards also would
  be stripped down, without services, to 50KB.
• While the design of the ORB may vary from vendor
  to vendor, the way CORBA objects communicate with
  the software would be the same

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References of CORBA for Embedded Systems

• A set of references can be found at
  http//dpe.postech.ac.kr/juht/emcorba/
• OMG Members Plot Embedded CORBA Services By
  Antone Gonsalves, PC Week February 27, 1998