Friday, July 08, 2005

About Service Discovery Architecture

Service Location Protocol: Directory Agents are the renaming of MGs or various central authorities. Service and User Agents resides on the mobile devices and work the same as a subset of the CORBA framework components.

JINI: Has a Jini Lookup Service (JLS), exactly as MG.

Universal Plug and Play: UPnP uses SSDP over HTTP in two fashions, UDP(HTTPU) and UDP(HTTPMU). A service joining can unicase or multicase to the default selected set of clients or peers about it's arrival in the network and start of service. A client can directly contact a server based on URL or can multicase a request. UPnP seems to be a resonably good one since its architecture says 'NO' to centralized directory server.

SALUTATION: The salutation architecture defines another centralized entity as Salutation Manager (SLM), exctly as SLP's Directory Agent, or JINI's JLS or Nomadic's MG.

About UpnP
Hence, I am going to write or delve deeper into Universal Plug and Play only in the further blog contents. UPnP has five steps in all:
  • Discovery:
  • Based on SSDP over HTTP. When a device comes it multicast to the control point about it's service description. When a control point comes, it searches for devices of interest on the network.
  • Description:
  • After discovering the device, the control center retrieves the device (I assume service too) description from the URL provided by the device.
  • Control:
  • Control point sends control message to the control URL for the service.
  • Eventing:
  • In case service changes any of the service variables or other information about itself, it informs the control center with a event message about the change.
  • Presentation:
  • Some devices provides a URL like MBeans to allow a user to view device status or control the device.
    About SLP
  • Advantage factor of SLP is that it supports service browsing and string based query.

  • About Nomadic
  • Cooperation among MG's in nomadic environment is also a good thing to do.

  • Few Points
    Advantage of Nomadic over MANET are:
  • Scalability

  • Response Time

  • Load Balancing
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