Jini Overview and Specification

1
Jini Overview and Specification

• Presented by Jas, Alvin Chris
• CSE 291-B
• May 29, 2003

2
Jini - Introduction

• Jini technology allows devices to dynamically
  establish communication to share and exchange
  services across a network.
  
• Provides simple mechanisms which enable devices
  to plug together to form an impromptu community
  (federation)
  
• Lesson in Political Science In a federation,
  most power lies in local authorities. Federal
  authorities ensure that local authorities work
  together.
• Each device provides services that other devices
  in the community may use.
  
• These devices provide their own interfaces which
  ensure reliability compatibility.
  

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Jini - Introduction

• Jini is an extension of Java
• Java consists of one virtual machine
• Jini is a kind of virtual network
• Jini Devices must have processing power or
  memory.
  
• Otherwise controlled by another device.
• Relies on existence of a network of reasonable
  speed connecting these devices.

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Key Concepts

• Services
• An Entity used by person, program, or another
  service. May be a computation, storage, a
  communication channel, etc. You knowa service!
  
• Jini system consists of services that can be
  collected to perform a particular task.
  
• Services can be dynamically added or withdrawn
  from the system as needed.
  
• Services Communicate using a service protocol
  which is a set of interfaces written in Java.
  

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Key Concepts

• Lookup Service
• Major point of contact between users of the
  system and the system.
  
• Finds and adds services to the Jini Federation
• Maps functionality to a set of objects in Jini
  that actually implement the service
  
• Can include other lookup services (hierarchy)
• Can for bridges to other lookup services.
• Services added using two protocols
• Discovery locates appropriate lookup service
• Join join lookup service.

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Key Concepts

• Java RMI
• Provides communication between services
• Extension to normal remote procedure call.
• Passes not only data, but entire objects and
  code.
  
• Provides Simplicity
• Code can be encapsulated in an object and can be
  passed from service to service.

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Key Concepts

• Leasing
• Access to many services are lease based.
• Guarantees access to a service for a negotiated
  period of time.
  
• Services can be exclusive or non-exclusive.
• Transactions
• A series of operations to be performed.
• Within a single service or spanning multiple
  services.

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Key Concepts

• Security
• Built on the twin notions of a principal and an
  access control list.
  
• Jini services are accessed on behalf of some
  entity (principal) which traces back to a user of
  the system.
  
• Check objects access control list to determine
  permissions to use a particular service.

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Key Concepts

• Events
• Ability to notify objects when a particular event
  occurs.
  
• Could trigger new task/transaction

10
Components

• Three main components
• Infrastructure
• Programming Model
• Services
• Tend to get blurred, but just an extension of the
  virtual machine concept.

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Components

• Infrastructure
• Discovery Join Protocol
• Define way services become part of Jini System
• Java RMI
• Base language with which services communicate
• Security Model
• Define how entities are identified and how they
  get rights to perform actions.
  
• Lookup Service
• Marketplace for finding and offering services.
• Entries in Lookup Service are objects written in
  Java. Objects can be downloaded and act as local
  proxies.

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Components

• Programming Model
• Sets of interfaces designed to extend the usual
  single virtual machine model.
  
• Leasing Interfaces
• Adds time-based interface to resources.
• Event and Notification Interfaces
• Enable event-based communication between services

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Components

• Programming Model (Cont)
• Transaction Interfaces
• Coordinates the actions of a group of distributed
  objects in a two phase system
  
• Voting Phase
• An object votes on whether it has completed it
  portion of a task and is ready to commit.
  
• Commit Phase
• Coordinator issues a commit request to each
  object.

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Components

• Services
• Consist of objects coded in Java
• Can be made up of other objects
• Has an interface that defines what a service is
  capable of doing
  

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A Closer Look at JINI

• Similar Technologies
• Limitations of JINI
• Case Studies
• Current Status

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Similar Technologies

• UPnP, Salutation, NINJA
• Common Object Request Broker Architecture
• CORBA is a specification for a Distributed Object
  System
  
• RMI vs CORBA
• performance and portability tradeoffs
• Distributed Objects vs Distributed Services
• Can be used in complementary fashion?

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Using CORBA with JINI
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Limitations Service Lookups

• Lookup Servers vs Name Servers
• Query by service or name
• Exact Matching
• ServiceTemplate / ServiceRegistrar provide
  limited expressiveness (i.e. for range queries)
  
• Fault-tolerance
• No defined policies for system recovery

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Limitations Low-Resource Hosts

• Servers Suns reference implementation of Lookup
  Service consumes 3 MB storage
  
• Clients Limitedness of lookup interface can
  require a lot of unnecessary overhead
  
• Is this really a problem (given the success
  stories)?

20
Case Studies Who uses it?

• Siemens
• Toshiba
• Samsung
• Kinkos
• Hewlett Packard
• AOL
• Adaptive Networks
• Ericsson

• Quantum
• Seagate
• 3COM
• Cisco
• Xerox
• Novell
• Nokia
• Philips
• Sony
• Motorola
• Kodak
• Sharp
• Canon

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Case Studies Success Stories

• 4D Networks Application Services for the
  Web Built on Jini Network Technology.
  
• Appropria Jini Technology Brings
  Mission-critical Information Out of the Silo.
  
• Entegrity Solutions Major Online E-commerce
  and Enterprise Solutions Company Rely on Jini
  Network Technology for Secure E-Commerce.
  
• Eko Jini Technology connects medical data
  and equipment dynamically and reliably.
  
• FETISH Federation Jini Network Technology
  Links Online Travel Services.
  
• Lightflow Jini Network Technology Adds
  "High Touch" to Online Shopping.
  
• Maui High Performance Computing Center Sun
  Architects Jini Network Technology Infrastructure
  for Military Simulations.
  
• Procoma An Innovative Solution for
  Commerzbank AG with Jini Technology.
  
• Raytheon Open, Adaptive, Self-Healing
  Architecture for DD21.
  
• U.S. Army Reliable Battlefield
  Communication Using Jini Connection Technology.

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Case Studies Success Stories (cont.)

• We believe that the Jini and Java technologies
  will dramatically change the way DD 21 and future
  Navy systems are developed. The spontaneous
  community capabilities of Jini will lead to much
  more reliable, capable and maintainable systems.
  The development and integration cycle will be
  reduced significantly, and the use of commercial
  components will finally be cost-effective. --
  Lead Systems Engineer for DD21, Raytheon
• "The cost of manually implementing what Jini
  network technology is providing us would have
  been prohibitive both from an actual cost
  perspective (person-hours to build) and time
  perspective (time to market)," said Horvath.
  "Jini technology's increasingly mature and
  well-documented capabilities would be very
  difficult to reproduce. The use of Jini
  technology allows our team to stay focused on the
  problem space of AssureDelivery, and not on
  implementation details of the underlying
  distributed service." -- Director of Product
  Development, Entegrity Corp.

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Current Status

• Increased Deployment Jini Technology
  Licensees, Including Heartlab Inc, Templar Corp,
  Valaran Corp, FETISH Federation, and Cysive Inc.,
  Turn to Jini Technology to Address Dynamic
  Networking Challenges (May 7, 2003)
• StandardizationJini Community Approves the
  ServiceUI API (May 7, 2003)
  

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Current Status (cont.)

• Open Issues
• Network Scalability In theory, a JINI systerm
  can scale if it uses a hierarchy of lookup
  servers (like DNS), but no actual wide area
  JINI network has been deployed. But is this even
  relevant?
• Generality Can well-defined interfaces be
  established for all types of services besides
  simple examples like printers and cameras?

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Jini SensorNets

• Can they benefit from each other?

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Benefits of Jini on SensorNets

• Sensor networks could benefit from having a
  virtual machine on each platform so that not
  every platform required special code
  
• Allows for single deployments with multiple
  sensing applications
  
• Dynamic addition/removal of services
• As platforms with newer sensors come onboard, the
  network would automatically adapt to support
  them
  

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Divergences

• Jini seems to imply high connectivity and high
  bandwidth
  
• Code is dynamically downloaded to the node
• Currently, this is too much to expect from nodes
• Jini makes no attempt to address power
  consumption issues
  
• Asynchronous communication implies the radio be
  on most of the time
  
• Automatic discovery and handshaking looks costly
• Perhaps this is why Jini hasnt taken offmost
  embedded devices are on a power conscious diet

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Future Work

• Since they expect Jini to take off for embedded
  devices which have significant power constraints,
  Jini should be made aware of these constraints
  
• Should prioritize the needs in sensor networks
  and eliminate marketing features found in Jini
  

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Discussion Questions

• Should sensornets adapt and conform to Jini-like
  standards or should sensornets use a simplified
  version of Jini?
  
• How much overhead is acceptable for sensor
  networks in terms of communication and
  computation?
  
• Can virtual machines be made to have virtually no
  overhead and still be powerful?