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Mobility-Enhanced Network Services

Mobility-Enhanced Network Services. Todd Hodes, Randy Katz Computer Science Division University of California, Berkeley http://www.cs.berkeley.edu. Scenario. Enter campus, check PDA for list of services e.g., obtain campus map, check building location. Soda Hall. Current Cell.

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Mobility-Enhanced Network Services

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  1. Mobility-EnhancedNetwork Services Todd Hodes, Randy Katz Computer Science Division University of California, Berkeley http://www.cs.berkeley.edu

  2. Scenario • Enter campus, check PDA for list of services • e.g., obtain campus map, check building location Soda Hall Current Cell

  3. Enter Soda Hall • Available services change • e.g., Current map changes “foyer services”

  4. Move to Auditorium “auditorium services” • See additional services presented • e.g., Obtain VCR and A/V switching controls • e.g.., Existing light switch UI widget remapped to local lights “foyer services”

  5. Print Notes • Select printer; location noted on current map • Print & retrieve file, return to auditorium

  6. Location-based Services • Maps + Coarse-grained location tracking • Printers, lights, audio/video equipment • DNS, NTP • many others...

  7. Outline • Requirements • Architecture • Location & Scope • Services as Partitioned Application Components • Prototype Applications • Summary • Future Work

  8. Requirements 3 clients objects ? 1) Non-intrusive Mobile Devices 2) Remote-Controllable Devices / Apps 1 2 3) Service Discovery 4) Transducers between objects and clients 4

  9. 1) Client Devices • Use of small mobile devices • promotes goal of “non-intrusive” usage • allows users to interact with their “usual” device rather a “new” (local) one

  10. Remote Control This? Or this?

  11. 2) Controllable Objects device • Define and create specific API for control of apps • Expose control interface over the network while separating/minimizing UI assumptions RS-232 control interfaces accessible via IP computer IP

  12. Example Devices: UCB CoLab Echo Canceller Mic amp TV monitor, Camera, & Speaker sets A / V switch Scan Converters Computers Receiver Serial mux LiveBoard Not shown: VCR, power control, ON-AIR sign, WaveLAN base station, ...

  13. 3) Service Discovery clients objects • Advertise, register, & query • Scalable management of hierarchy of available services • Scoping, rate-limiting for wide-area • Naming query register ? Service Discovery Service advertise Other Services . . . . . .

  14. (header) SIP IP addr port ticket application-specific payload … Scoped Discovery Bootstrap • Mobility beaconing is an announce/listen protocol • unify with a service location announce/listen protocol • announced data is location information • Advertisements (push) vs. queries (pull) • push: user anonymity, power, traffic • Contrast announce/listen with lookup-based schemes • adaptive scoping/forwarding (vs. DHCP) • no root servers (vs. DNS) • granularity varies with subnets, not area; no additional hardware required if connectivity assumed (vs. GPS) beacon packets

  15. Scoping Heuristics (scoped) beacon with ticket request + ticket • Tickets included in scoped beacons • For local per-service access • Without ticket, services are inaccessible • For local service directory (cache) access • Without a received beacon, contents (and existence) unknown

  16. 4) Transducing Interfaces • Map between object and client interfaces at application proxy • remap endpoints & data types, aggregate/subset, compose • Exploit: • COM/Java Beans-style introspection to discover objects’ interface definitions or explicit Interface Specifications • exposed indirection between client app and device (control protocol) to vary UI Application Proxy Client Device Device Proxy Wireless Wired IP RS-232

  17. On-the-fly Transduction • Utilize interface specification for on-the-fly UI generation/modification • Still can use existing client-specific UI code Application Proxy Client Device Device Proxy Wireless Wired IP RS-232 Generation Process Original or Generated UI Control Interface and/or Existing UI Code

  18. Remapping on off • Client UI data type to that expected by control interface • Current interface widget(s) to new servers • Control messages to other control messages (boolean) (enumerated) 0.0 1.0 0.5 (real)

  19. Aggregate or Subset • Create custom UIs that can use a portion of the functionality from one or more control interfaces • controllable objects/servers remain independent Aggregate Interface Definitions Application Proxy Client Devices Device Proxies

  20. Compose • Compose device/server interaction behind unified interface • Create complex behaviors from independent controllable objects/servers Aggregate Interface Definitions Application Proxy Client Devices Device Proxies

  21. Application Interfaces Summary • Allow multiple possible interfaces • Match heterogeneity in client devices • Match differences in available sevices • Mach per-user variations to suit differing usage models • Build complex behaviors from independent components • Transparent widget remapping of data type and endpoints • Feature subsets & aggregates • Composition

  22. Soda 405 Testbed Service Discovery Service

  23. Screenshots Service Interaction Client Monolithic A/V controller

  24. Screenshots (cont.) Lights Map with Exported Object Locations

  25. Screenshots (cont.) Audio / Video Switching Camera Control

  26. Screenshots (cont.) Video Monitor Switching (RVIC client & server)

  27. Detailed Example: RVIC • “Remote-controlled VIC” • Removes the UI from the monitor, places it in the user’s hand • vic’s UI overhead is useless if not used at a desktop • Reduces vic’s video window configuration complexity by supporting “standard configurations” • Messaging style: • idempotent, string-based • use announce/listen for reliability, eventual consistency

  28. RVIC Messages • RoomServer Messages: • Get SessionList [scope attribute] • Get MonitorList [scope attribute] • Get SourcesList <session> • InitMonitor <monitor> • Get RoomPresets • InitRoom <preset> • RvicServer Messages: • Get MonitorConfigs • Set MonitorConfig <configSpec> • Set VideoWindow <windowSpec> <source>

  29. RVIC Message Data • [scope attribute] : • from Service Directory bootstrap beacon • address/port + ticket • or hierarchical scope attribute string for conversion to addr/port • “…/Berkeley Campus/Soda Hall/326 Soda” (TBD) • <session> : SDP session name • <windowSpec> : integer window number, with windows ordered from top to bottom then left to right • <source> : a CNAME of a session source

  30. Detailed Example: RVIC (cont.) • Request rate and Consistency update scaling: • Eventual consistency via announce/listen • Exposes basic tradeoff in latency/bandwidth • update state on each action: minimize latency • rate-limit updates via timers and population estimation (a la SDP): tight bandwidth control • Multi-user policies atop mechanism: • “Free-for-all:” no locking • Dedicated controller: coarse locking • Rotating controller: fine-grained locking • Voting: no locking, but latency issues (c.f., SCUBA)

  31. Summary An architecture and prototype system for composable mobile services • IP Dial Tone isn’t enough • Deploy services, provide seamless access • Embed location information into data networks • Variable application interfaces • discover interfaces, move GUIs • transduce to reduce need for a priori interfaces • Used by instructor and students to control an augmented classroom (UCB CoLab)

  32. Continuing Work • MASH collaboration laboratory (326 Soda) • MBone video and audio • Conference control elements • Pilot PDA + Metricom interface implementation • User Interfaces (with J. Landay, M. Newman) • Presentation of controls • Behavior specification • Reconciliation of conflicting behaviors • Extend discovery beyond local-area • hierarchy, scoping, union/intersection

  33. Related Work • Mobile IP, Overlay Networking • Service Location Protocol • PARCTab, Active Badges • Application Partitioning (Rover, Wit, …) • Proxies/Gateways • DHTML, Universal Remote Controls • Location-based applications (Mobisaic, …) • Distributed object systems (CORBA, DCE, …)

  34. Device Mobility • Mobile IP, Overlays

  35. Composing Interface Definition • Create complex behaviors • From independent controllable objects/servers • UNIX pipe / HTTP proxy model • Exploits exposed application interface definition and indirection • Remap an RPC to multiple RPCs on-the-fly Application Proxy Client Device Device Proxy Device Device Proxy

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