Service Discovery in Home Environments KM-/VS-Seminar Wintersemester 2002/2003 Björn H. Gerth Betreuer: Muhammad Khan

Structure Home Environments, Service Discovery Jini Universal Plug and Play (UPnP) Salutation Home Audio/Video interoperability (HAVi) Summary & Conclusion Disk-centric and client/server computing: central connection points, high amount of administration Addition of devices may require shutdown/reboot of network Loose coupling: away from configured environments to foreign networks with unknown infrastructures Easy integration/removal: by simply plugging devices in or remove them, no administration desired

Home Environments Lots of electronic appliances with microprocessors Communication, interaction, share of services and functions Service discovery: devices can find services offered by other devices Middleware: software that connects devices and provides service discovery

Smart home environment Goals of service discovery networks: Network-centric computing instead of disk-centric computing Collection of services and clients instead of applications and peripherals Easy integration and removal of devices Easy communication between devices House of future with smart environment Devices help us with daily life User interaction for all sorts of devices from any component with display capabilities from anywhere in the house Digital technology to enhance entertainment experience Remote access of home appliances through the internet Disk-centric and client/server computing: central connection points, high amount of administration Addition of devices may require shutdown/reboot of network Loose coupling: away from configured environments to foreign networks with unknown infrastructures Easy integration/removal: by simply plugging devices in or remove them, no administration desired Help with daily life: e.g. fridge orders food through the internet, no visit to supermarket necessary; alarm clock connected to heating system and coffee machine Component with display capabilities: PDA, cell phone, TV/remote control, PC Digital technology: includes digital broadcasting (radio and TV [set-top boxes])

Jini Developed by Sun Microsystems Open license, but fee for commercial use Architecture based on Java Federation of easily pluggable and removable components Low level of administration Avoidance of single points of failure Home environments: Useful, but few interfaces for home appliances have been specified Federation: network is made up of several federated control points, subsets of devices are only registered with one or a few control points => advantage concerning excessive expansion of networks (not given for home env.) Administration: a device has to be provided with an IP address Single points of failure: Breakdown of one device affects the network as little as possible Java: Makes heterogeneous devices homogeneous through JVM, provides inherent safety and platform independence Home environments: missing interfaces prevent vendors from building devices with Jini capabilities

Jini Service Object / Proxy Proxy: Java code object respresenting interface to its service; provides service attributes Service object in Java code: high abstraction level Client downloads proxy to use the service Communication proxy <-> service is not specified by Jini

Jini Lookup Service LUS: Allows spontaneous networking At least one LUS must exist in Jini network Devices offering service(s) register with LUS (discovery and announce protocols via TCP/IP), then upload their service object Client queries LUS for matching proxy, i.e. matching Java type and desired properties in service attributes Client downloads proxy from LUS and communicates with the LUS directly

Jini Leasing Resource allocation and deallocation throughout the network Grant of usage of resource for a limited time Examples: Service registration lease Use of memory, disk space or display capabilities of other devices Event subscription Advantages: Deactivated services Recover from temporary breakdown of network Cancellation of leases Grant of usage: Renewal of lease after time ran out is necessary to continue usage of resource Service registration lease: Service registering with LUS gets lease, if lease is not renewed LUS assumes service was removed from network Use of resources: Use of all available resources throughout the network possible, not only of client and service; service does not have to use leasing for ist own resources Event subscription: Client registers at LUS for a certain event (e.g. a desired service registers itself with the LUS), recieves information from LUS when event happens Deactivated services: Services may not use processing power or memory, wake-up call by LUS Recover: time of breakdown shorter than lease period => resource allocation still valid afterwards Cancellation of leases: if resource in use is scarce

Universal Plug and Play (UPnP) Developed by UPnP Forum, led by Microsoft Open source Based on open protocols available almost anywhere OS and language independent Targets small to medium size IP networks UPnP included in Windows XP Small IP networks: Small office, home environments

UPnP protocol stack Discovery: Joining device uses SSDP (Simple Service Discovery Protocol). Device sends out multicast advertisement Multicast advertisement through HTTP over mutlicast UDP (HTTPMU) Unicast replies Control Points correspond to Jini’s LUS, but are not required for the UPnP network A control point which joins the network sends out a multicast search message SOAP (Simple Object Access Protocol) used to invoke actions of a device being controlled SOAP message sent to the SOAP control object of the service of the device, which returns action-specific values

UPnP description of services Device contains set of services corresponding to functional units Description stored in XML file, location given in unicast reply List of actions to access service List of variables expressing run-time state of service Update messages formatted with GENA Description may include Presentation URL Higher level UI at URL Displays status or may allow user to change it XML file: location given in unicast reply the service sent out previously GENA: General Event Notification Architecture Update message: Received by all control points or clients which subscribed to receive this information Higer level UI may be loaded into a browser

UPnP configuration, AV Configuration: DHCP or AutoIP Consumer electronics: UPnP AV Set of device and service definitions for devices handling entertainment content Media Server: Has access to entertainment content Media Renderer: Can render such content on local hardware Control Point: Coordinates Servers and Renderers SOAP: Simple Objects Access Protocol DHCP: Dynamic Host Configuration Protocol AutoIP: random choice of IP address from reserved range, detection request whether address is already owned by other component Media Server: e.g. a VCR Media Renderer: e.g. a TV Control Point: is not involved in actual transfer of content, so that any transport protocol and supported content format can be used

Salutation Developed by Salutation Consortium Devices available since 1996, but mostly office components Support of multiple infrastructures

Salutation architecture Discovery: Device registers with nearest Salutation Manager Registration: SLM keeps registry about all services and clients registered with it Client queries nearest Salutation Manager Certain types and sets of attributes have to be matched by service Query: Salutation Manager redirects search to other SLM Transport Managers Offer reliable communication channels Salutation Manager connected to one Transport Manager per infrastructure Communication between SLM and TM: protocol independence

Salutation Functional unit: One service of a device Three ways of communication for components Native mode Emulated mode Salutation mode Salutation Lite: Reduced version of architecture for small devices Suitable for devices with limited storage space, low communication bandwidth and little power consumption Native: direct communication Emulated: SLM carry messages between devices => protocol independence Salutation mode: Special format required for messages, well-defined standards for interoperation of functional units

Home Audio/Video interoperability (HAVi) Focuses on consumer electronics (CE) Developed by HAVi organization, founded by eight well-known CE companies (e.g. Sony, Grundig) Networking software specifies protocols to be used by components Allows multi-directional audio/video streams and share of resources Narrow product range: Easy for vendors to develop interfaces and meet demands of audio and video

HAVi architecture DCM: Device Control Module represents each device. Contains set of Functional Component Modules (FCM), numerous such FCM have already been defined for HAVi (e.g. tuner of a TV). Messaging system: Performs exchange of information between devices Registry: services have to register here, clients query Registry for services matching a set of criterias Communication Media Manager: provides transport mechanism, abstracts network activities IEEE 1394: interconnection medium (aka i.Link or FireWire). Allows speeds of up to 400 Mbit/s Event: change of state of software element or of the network Event Manager: notifies all software elements registered with it about desired events; forwards global requests to other Event Manager in the network DCM Manager: hosts DCM of a foreign device Stream Manager: configures internal connections (within device) and external connections (between devices). Streams between FCMs of devices; Manager allocates bandwidth and channel numbers. Resource Manager: handles use and release of FCMs within a device Havlet: A Java application that can be extracted from the DCM of a device. Show UI on a Java-enabled display device

HAVi configuration FAV: Full audio-video device IAV: intermediate AV device BAV: Base AV device LAV: Legacy AV device, not designed for HAVi (e.g. older device), can still be integrated into network FAV or IAV provide DCM for BAV and LAV Network not possible with only BAV and LAV

Summary

Conclusion Most service discovery solutions still in developmental stage Product availability Mobile devices Interconnecting bridges between architectures Thank you for your attention Questions & Discussion Product availability: Jini (scarce), UPnP (Windows XP, SDKs), Salutation (office automation), HAVi (scarce) Mobile devices: All systems do not address mobile devices well, although they are important for home environments Interconnecting bridges: e.g. HAVi and Jini