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TU / e. Service Discovery Mechanisms: Two case studies. Control point. UPnP. Device. Terminal Domain. wireless CORBA. Host. Service Discovery Mechanisms: two case studies / IC’2002. TU / e. Software Architectures for interoperability. Application. Application. network

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TU / e

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  1. TU/e Service Discovery Mechanisms: Two case studies Control point UPnP Device Terminal Domain wireless CORBA Host Service Discovery Mechanisms: two case studies / IC’2002

  2. TU/e Software Architectures for interoperability Application Application network manager network manager (a)Middleware bases on API, network issues are kept away Application Application specific protocols specific protocols transport layer transport layer (b) Aspects of the protocol and of the underlying network technology carry through into the application. Service Discovery Mechanisms: two case studies / IC’2002

  3. TU/e Service recognition • A service can range from the unstructured use of • a device to the structured control of well-defined • functions. • How the service is made available: • - Via the driver provided by the device • - Via the interface definition document (XML) • - Rely on standardized protocols • Service discovery mechanisms can be classified: • - Centralized • - Distributed Service Discovery Mechanisms: two case studies / IC’2002

  4. TU/e Service Discovery in UPnP(1) The Universal Plug and Play Protocol (UPnP) uses the Simple Service Discovery Protocol (SSDP) to locate the service in IP networks. advertising searching Device 1 Control point 1 Internet searching advertising Device 2 Control point 2 • Both searching and advertising use HTTP Multicast. • The response uses HTTP Unicast. • UPnP targets to home-networking environments. Service Discovery Mechanisms: two case studies / IC’2002

  5. TU/e Service Discovery in UPnP(2) UPnP uses the context-based mechanism to make the control point understand about the device and its services: - At the device side, the device and its services are specified in XML files. - After processing SSDP, the control point downloads these files, parse them to fully understand the device. Service Discovery Mechanisms: two case studies / IC’2002

  6. TU/e Service Discovery in UPnP(3) A remote UIClient controls a TVDevice UIClient TVDevice UPnP API for Control point API for Device Java Virtual Machine Java Virtual Machine Operating system Operating system IP IP Network IP Network • UIClient and TVDevice use SSDP to discover each other. • UIClient retrieves the TVDevice description and get a list of • associated services. • UIClient retrieves the service descriptions of interesting services. • UIClient starts interacting with TVDevice. Service Discovery Mechanisms: two case studies / IC’2002

  7. TU/e Service Discovery in CORBA(1) CORBA uses a centralized Naming or Trading Service to locate the services available on the network. register access Access Bridge Shop 1 Cient 1 Internet Access Bridge access register Shop 2 Client 2 • Services are registered at a Naming Service • Clients discover services by accessing a Naming Service • Each Access Bridge can contain its own Naming Service • Wireless CORBA targets the mobile phone environment Service Discovery Mechanisms: two case studies / IC’2002

  8. TU/e Service Discovery in CORBA(2) • CORBA uses pre-defined API interfaces to allow clients • to access services that use supported interfaces: • Each service uses a certain API interface • Clients support a limited set of API interfaces • API interfaces are not extensible • Problem: this does not scale well • Solution: protocol on top of CORBA • Example: Remote User Interface protocol Service Discovery Mechanisms: two case studies / IC’2002

  9. TU/e Service Discovery in CORBA(3) A remote UIClient controls a TVDevice Remote UI UIClient TVDevice GIOP ORB ORB Operating system Operating system IP IP Network IP Network • UIClient and TVDevice use Naming service todiscover each other. • UIClient subscribes to the TVDevice and get an initial • user interface description • User performs actions through the user interface renderedby UIClient • TVDevice handles requests from UIClient and returns updates for the user interface. Service Discovery Mechanisms: two case studies / IC’2002

  10. TU/e Conclusion • UPnP and wireless CORBA use clearly different models for • service discovery. Wireless CORBA belongs to (a) and • UPnP belongs to (b) – slide 2. • UPnP uses HTTP Multicast – a distributed method. • Wireless CORBA relies on the infrastructure available within • it to publish services, like the use of naming service • – a centralized method.. • Scalability in both technologies is limited. In UPnP because of • the restriction of the multicasting protocol. In wireless • CORBA this is due to the limitation of API interfaces. • For wireless CORBA, it is unclear how services are easily • discovered on other terminals that are nearby. Service Discovery Mechanisms: two case studies / IC’2002

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