Thursday, December 29, 2005

Dimensions of Service Discovery

Need of Common Platform: With heterogeneous protocols supported by various entities involved in the virtual network, there would be diversity in service discovery protocols; hence a common platform or protocol establishment is a must requirement for enabling interoperability among service discovery protocols.


  • Service and Attribute Naming: Namespace based to avoid collisions and sustain uniqueness, human friendly service names, no usage of predefined templates for service names and attributes to support a common platform vision.

  • Initial Communication Method: Unicast communication can only be used service discovery clients have specific prior configuration, hence such communication is infeasible in MANETs. A few Multicast messages to the directory, client can than proceed by explicit unicast messages. Link layer Broadcast can also work for a hop of distance.

  • Discovery and Registration: Announcement based seems to be less suitable as client needs to listen and maintain a list of available services. Query based suits good to MANET and a client need not to process uninterested announcements.

  • Service Discovery Infrastructure: Directory based models have a dedicated directory that maintains, processes, announces service information. This model is good when hundreds and thousands of services are incarnated in the network. Non-Directory based models have no dedicated components. When a query arrives, each service processes it; and replies if it matches with the desired one. A client can record service information for future usage.

  • Service Information State: Soft State has an explicit service demise announcement; services too have explicit lease declaration in them, a graceful removal from the directory and announcement from the service itself. Hard State requires few service announcements and housekeeping. However, clients require to poll services to make sure that they are alive.

  • Discovery Scopes: Proper discovery scopes minimize unnecessary computation on clients, services, and directories. Network topology based, User Role based, and Temporal Context based can be categorization of scopes.

  • Service Selection: Although discovery scope can limit the number of service matches, there can a list of services available, and a selection could be required from them, Selection can be from user as manual, prompting user to choose or can be automatic, where the discovery protocol selects the service. This approach simplifies client programs and requires little user involvement. Good aspects that can be handled in automatic service selection are network hop distance to the service from requester client, load factor on services, service side robustness etc.

Wednesday, December 28, 2005

Pervasive Computing

I found a very good definition of pervasive computing:

It is characterized as a combination of distributed systems and mobile computing but also augmented by smart spaces, invisibility, localized scalability and uneven conditioning. A more detailed research space includes user intent, adaptation strategy, high-level energy management, client thickness, context awareness, balancing proactivity and transparency, privacy and trust.

When Edison finally found a filament that would burn, did he see the possibility of silent but pervasive electrical current flowing throughout our homes, cars and communities?

Tuesday, December 27, 2005

Known Issues

  • Mobile phones do not yet support an IP stack over Bluetooth. Devices which only support Infrared or ZigBee would be disconnected from the virtual network created by framework.

Monday, December 05, 2005

Live on Wireless

Amazing new world utilities coming up now a days, below are a few to seek out,

  • Handheld equipment hoping on reconfigurable frequencies defined by middleware stacks (Extremely useful in military applications)

  • Context aware applications ranging from vehicular computing to Sensor based Ad Hoc computational systems, that is your car system can automatically adapt its configurations (may be speed in automatic drive, transmission ratios of gear box, audio tracks of your sound system) according to the profile of the user driving the car

  • Server side components for handheld devices

  • Virtual Home Imaginations (HP is going great work in it)

  • Frameworks to support heterogeneous MAC layer environment, so that your handheld can now navigate seamlessly on Bluetooth, CDMA, GSM, 802.11 (a-g), even to 3G networks

  • Dynamic service composition and delegation, such that your handheld can request a service and according to the request attributes, hosted services can jointly combine and process the request.

  • and Disconnection operation to name a few (a scenario can be like, your doctor can asynchronously prescribe you diet of specific calories even when you are not in doctor's clinic and you can view that on your mobile or laptop while taking a morning walk in some lush green vally...