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Overview of Jini

Overview of Jini. CS294-10 Fall 2000 Jason I. Hong. Motivation. Coordination framework Simple, seamless, and scalable interoperability Network "plug and play" with minimum admin Networked software and hardware provide services Any device can find and use existing services

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Overview of Jini

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  1. Overview of Jini CS294-10 Fall 2000 Jason I. Hong

  2. Motivation • Coordination framework • Simple, seamless, and scalable interoperability • Network "plug and play" with minimum admin • Networked software and hardware provide services • Any device can find and use existing services • Example scenarios • "Find all nearby color duplex printers" • "Start brewing coffee five minutes before my alarm clock goes off" • "Let my cell phone use the car speakers"

  3. Network Network Network One Way Scenarios Might Be Done Today Printer Service Desktop PC Coffee Maker Alarm Clock Service Cell Phone Stereo Speaker Service

  4. What Jini Proposes Lookup service Printer Service Desktop PC Network Coffee Maker Alarm Clock Service Cell Phone Stereo Speaker Service

  5. What Jini Provides • Middleware interfaces + implementations • Programming model for distributed services • Federating and using services • Core to Jini is lookup service • Service for registering, finding, and leasing other services • Uses a well-known multicast address

  6. Service Registration Lookup service 1. Find Lookup Service 2. Return stub to lookup 3. Return stub to service Network Alarm Clock Service

  7. Service Leasing 1. Find Lookup Service Lookup service 2. Return stub to lookup 3. Query for service 4. Service returned Network Coffee Maker Alarm Clock Service Find interface Printer (duplex=yes, color=yes)

  8. Using Services Lookup service Network Coffee Maker Alarm Clock Service Can use any protocol to communicate to service (or stub can contain service itself!)

  9. Some Cool Things with Jini • Can form ensembles of lookup services • Pass requests up hierarchy (like DNS) • Leasing model handles service failures • Flexible search on properties • Distributed transactions (two-phase) • Distributed events

  10. Some Problems with Jini • Requires a priori knowledge of service interface • Everyone must agree on same service interface • Ex. "Printer" and "Speakers" interface • Currently requires Java VMs everywhere • Needs lots of memory and processor power • Complexity of code

  11. Some More Problems with Jini • No good way to attach user interfaces • Lack of security mechanisms • Single point of failure for service lookup

  12. Competing Technologies • Universal Plug and Play (UPnP) • Aim is to be independent of OS, language, and physical medium • UPnP relies on well-defined XML data formats and HTTP-based protocols • Jini relies on well-defined Java interfaces • UPnP philosophy: different APIs for each platform (no code download, higher startup, more reliable?) • Jini philosophy: "Write Once Run Anywhere" (code download, low startup, but less reliable?)

  13. Competing Technologies • Salutation • Aim is to be independent of vendors and network architectures (ex. Java, UDP, TCP/IP, HTTP) • Aim for platform, OS, and network independence • All service functions mediated by Salutation Manager • Completely open and nonproprietary architecture • Small footprint • Point-to-point service discovery (but can also do directory-based too)

  14. Further Reading • Jini Specification http://www.sun.com/jini/specs • Jini Developers http://jini.org • Universal Plug and Play http://www.upnp.org • Salutation http://www.salutation.org

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