KangseokPhDFirstPres entation

Information about KangseokPhDFirstPres entation

Published on January 30, 2008

Author: Quintino

Source: authorstream.com

Content

A Framework for Synchronous and Ubiquitous Collaboration:  A Framework for Synchronous and Ubiquitous Collaboration Advisor & Chairperson : Dr. Geoffrey Fox Committee Faculty : Dr. Dennis Gannon, Dr. Kay Connelly, Dr. Sun Kim Kangseok Kim [email protected] Computer Science Department Indiana University Outline :  Outline Motivation Research Issues Universal XGSP Collaboration Framework XGSP (XML based General Session Protocol) XRBAC (XML Role Based Access Control) XFloor (XML Floor Control) Experimental Results Contribution Future Work Research Issues I:  Research Issues I Heterogeneous community collaboration Most heterogeneous community collaboration systems cannot communicate with each other. e.g. H.323 <-> AG, AG <-> SIP We need wider range of collaboration by building integrated collaboration system, which combines collaborative applications as well as other collaboration into a single easy-to-use environment. Universal collaboration and access Mean capability of multiple users to link together with disparate access modes to access collaborative systems. Make systems more usable and more useful, and enable people to work together with others remotely. Research Issues II:  Research Issues II Access control in collaboration system The cooperation on the resources shared among a group of users may produce new results on the shared resources. Access control policies and mechanisms are needed to restrict unauthorized access to a variety of protected information and resources. Group coordination support As users try to manipulate shared application at the same time, a user may have to contend with other users for access to the shared application. To maintain consistent shared state at application level, we need to control competing accesses and mitigate race conditions for shared resources. Universal XGSP Collaboration Framework:  Universal XGSP Collaboration Framework Built on heterogeneous (wire, wireless) computing environment. Handle cooperation and communication among heterogeneous communities. Provide collaborative applications in the heterogeneous community collaboration. Shared event mechanism. Structured as three layers and six major components: node manager, session / membership control manager, access / floor control manager, policy manager, request and reply event message handlers, and communication channel. Universal XGSP Collaboration Framework Architecture:  Universal XGSP Collaboration Framework Architecture Collaborative Applications Node Manager Session/Membership Control Manager Access/Floor Control Manager XGSP Event Messages XGSP Event Messages XGSP Event Messages Request/Reply Handler Request/Reply Handler Request/Reply Handler Communication Channel Policy Manager Broad View Architecture:  Broad View Architecture Application Proxy Application Filter Conference Manager Message / Service Middleware (Broker) XGSP (XML based General Session Protocol):  XGSP (XML based General Session Protocol) Session means online workgroup of collaborators working with sharing various collaborative resources. Means control logic defined in XML. The control logic is used to manage presences and connectivity among collaborators in online session, and organize online workgroups (sessions or conference). To maintain consistent state information among sessions and collaborators in a coordinated way. We use query-dissemination interaction event messaging mechanism with publish-subscribe messaging service. provide a flexibility for adapting dynamic changes of collaboration states (creation and destroy of workgroups, and presences of participating users in workgroups) XRBAC (XML Role Based Access Control):  XRBAC (XML Role Based Access Control) RBAC is a scheme that describes access rights based on roles in an organization. Pros: ease of administration, scalable Cons: not flexible, not effective to fine-grained access control XRBAC Use roles based on users’ privileges and devices’ capabilities Chairperson-mediated interaction mechanism (request-response) mechanism Flexibility – adapting to the state change of collaborative resources at run time Fine-grained action - defined as the smallest interactive major events (semantic events) XRBAC Architecture:  XRBAC Architecture Chair node Request node Decision Response Access Request Conference Manager Message / Service System (Broker) Push Policy Push Policy KMC (Key Management Center) XFloor (XML Floor Control):  XFloor (XML Floor Control) Interaction management for synchronous collaborative application. In traditional face-to-face offline session, participants generally follow rules of etiquette or social protocol when they interact with each other. In online session, participants usually interact with each other using computer-mediated policies with CSCW (Computer Supported Cooperative Work) tools. Floor control policy and mechanisms have to be able to provide a floor on shared resource for only one participant in online session at any time. XFloor provides flexibility ranging from free-for-all to application specific floor control mechanism. Free-for-all (no floor) ex) Text-chat application Chairperson-mediated floor control mechanism ex) Shared whiteboard application Major event conflict detection function (Strictly conflict avoidance) Non-optimistic locking mechanism Two-player turn-taking mechanism ex) Collaborative chess game application Examples:  Examples Broker Major event (Moving object) Major event (Moving object) XGSP event XGSP event XGSP event Drawing event Drawing event Drawing event Text event Text event Major event (Moving object) XFloor Policy:  XFloor Policy Floor policy means how users request resources, how the resources are assigned and released. A set of predicate rules (policies) are defined in terms of request, response, and release to provide the floor for only one participant at a time. Request Users can request through the use of XFloor control tool Chairperson can directly assign a floor to collaborators Response If the floor is available, a chairperson assigns the floor to the floor requester. Otherwise, the floor request is queued into a floor waiting queue or can be denied. Release Floor is assigned to a requester waiting in a floor waiting queue in FIFO order Floor can also be released from directly chairperson or after a prefixed amount of time. XFloor Mechanism:  XFloor Mechanism Determination of types classified to access resources If the return type is “Implicit” -----> grant “Exclusive” ---> grant or queued “Shared” -----> grant or deny “Released” ----> grant If one of the elements does not exist in policy, then a type “Invalid” is returned into chairperson and the request is denied. Determination of whether an action in a request exists in current floor state information table, in other words, a request action conflicts with the action of current floor holder If the return type is “Exclusive” and request action exists in the floor state information table, then the request is queued. Otherwise, the request is granted If the return type is “Released” and a floor waiting queue is not empty, then the request is granted and the first request in the waiting queue is granted. If the return type is “Released” and a floor waiting queue is empty, then the request is granted Decision Procedures of XFloor Mechanism (strictly Conflict Avoidance):  Decision Procedures of XFloor Mechanism (strictly Conflict Avoidance) This guarantees the mitigation of race conditions of floor requests to shared application. Non-optimistic Locking Mechanism with Shared Whiteboard:  Non-optimistic Locking Mechanism with Shared Whiteboard Fine-grained locks are used to allow more concurrent activity among participants. Coarse-grained lock can be used to allow a participant to make more activities at a time. This mechanism guarantees that the consistency state at application level is maintained among participants. Request-Response Interaction Scheme between a Chairperson and a Floor Requester with Human-Computer Interaction:  Request-Response Interaction Scheme between a Chairperson and a Floor Requester with Human-Computer Interaction B R O K E R Access / Floor Control Manager Set Floor Set Floor Request Floor Request Floor Decision Decision (Grant, Deny, Queued, Release) Baseline Performance Results :  Baseline Performance Results SDSC NCSA CGL at IU 9.37 ms / 1 byte 54.65 ms / 60 KB 0.43 ms / 1 byte 13.79 ms / 60 KB 64.78 ms / 1 byte 353.44 ms / 60 KB 2.58 sec / 1 byte 28.43 sec / 60 KB 2.33 sec / 1 byte 22.18 sec / 60 KB 2.34 sec / 1 byte 22.86 sec / 60 KB Baseline Performance Results I:  Baseline Performance Results I Baseline Performance Results II:  Baseline Performance Results II Baseline Performance Results III:  Baseline Performance Results III Experimental Results I Transit Time in Request and Response of Sessions:  Experimental Results I Transit Time in Request and Response of Sessions Experimental Results II Transit Time in Request and Response of Sessions:  Experimental Results II Transit Time in Request and Response of Sessions Application (Whiteboard) Filter Architecture View :  Application (Whiteboard) Filter Architecture View Broker Filter Display Display Display Transcoding Graphical display data (Image or drawing object data) Pre-transcoding Problem: as new device or new type of application is added, all types of application have to be updated Post-trancoding Problem: wireless network and cell phone does not support the transfer of more than 60 KB Image Filtering Structure:  Image Filtering Structure Create Image Create Buffered Image Scale Image Convert to PNG Broker Whiteboard Application Filter Binary Image Data Binary Image Data Canvas Size (1024 x 768) Canvas Size (160 x 144) Binary Image Data Transcoded Binary Image Data Experimental Results III Transfer time of Image from Desktop to Cell phone:  Experimental Results III Transfer time of Image from Desktop to Cell phone Experimental Results IV Transfer time of Drawing objects from Desktop to Cell phone:  Experimental Results IV Transfer time of Drawing objects from Desktop to Cell phone 800x600 JPEG Image on Desktop vs. 158x134 PNG Image on Cell Phone :  800x600 JPEG Image on Desktop vs. 158x134 PNG Image on Cell Phone 60 KB (JPEG) 800 x 600 50 KB (PNG) 158 x 134 Shrunk size 0.2 x 0.2 Experimental Scenario Overview :  Experimental Scenario Overview Broker Access Request Simulator Chair Node (Decision Node) Request Node <RequestAction> Request arrivals with exponential Distribution with mean interarrival time (3 sec) <SetAppAction> Three different network combinations over three different locations (# of requests = 100) collaboration using only desktop devices (wired network) (# of requests = 100) 2. collaboration using only cell phone devices (wireless network) (# of requests = 100) 3. collaboration using desktops and cell phones together (wired + wireless network) (desktop (# 50) + (cell phone (# 50)) Overhead Timing Considerations:  Overhead Timing Considerations Total latency (Ttotal) = Waiting time (Tw) + Decision time (Td) + Network transit time (Tn = Treq + Tres) Broker Queue Decision Procedure Chair node Request nodes Decision Response Access Request Td Tw Tn = Treq + Tres Ttotal = Td + Tw + Tn Experimental Results V Mean completion time of a request vs. Mean request interarrival time (3000 milliseconds):  Experimental Results V Mean completion time of a request vs. Mean request interarrival time (3000 milliseconds) Experimental Results VI Reply + Non-Blocking vs. No-Reply + Blocking:  Experimental Results VI Reply + Non-Blocking vs. No-Reply + Blocking Reply + Non-Blocking No-Reply + Blocking Desktop : 9.77% (GridFarm), 1.12% (NCSA), 7.51% (SDSC) Desktop + Cell phone : 51.46% (GridFarm), 59.79% (NCSA), 59.83% (SDSC) Cell phone : 84.88% (GridFarm), 87.42% (NCSA), 86.96% (SDSC) Formal Verification by Colored Petri Net:  Formal Verification by Colored Petri Net We modeled the mechanisms (XRBAC and XFloor) and verified the modeled mechanisms in terms of mutual exclusion, dead lock, and starvation. The key part for the modeling and formal verification is to show consistent shared state at application level to collaborators by mitigating race conditions for shared resources We used Colored Petri Nets (CP-nets or CPNs) with time for the abstract modeling representation of the control mechanisms. XML based Control Mechanism Modeled by CP-nets :  XML based Control Mechanism Modeled by CP-nets Simplied XML based Control Mechanism Model:  Simplied XML based Control Mechanism Model Simulation Start Init Request Nodes Arrival Request Queue Policy Store Access Type Decision Service Real Code Send Decision Nodes Access and Floor Control Decision Service Current Floor State Information Table Critical Section Waiting List Queue Unlock Communication Service Contribution:  Contribution Building of Universal XGSP Collaboration Framework on both mobile device (cell phone) and non-mobile device (desktop) Defined general session protocol in XML (XGSP) This includes another colleague’s contribution on desktop Designed and implemented XRBAC The use of role based on users’ privileges and devices’ capabilities Scalability, Flexibility, Fine-grained access control Designed and implemented XFloor Provides flexibility from free-for-all to application specific floor control mechanism Chairperson-mediated interaction control with strictly conflict avoidance and non-optimistic locking mechanism Building of application filter for cooperation of heterogeneous types of whiteboard application Shared display model and shared event model Building of application proxy for Instant Messenger Shared event model Building of collaborative applications on cell phone Text Chat, Instant Messenger, Shared Whiteboard with Image Annotation Modeling of XML based control mechanisms (XRBAC and XFloor) To prove the correctness of the modeled mechanisms Future Work :  Future Work Fault-tolerant role delegation mechanism with role hierarchy policy A recovery approach from failure-prone system We already implemented polling (heart-beat message) mechanism. Design issues for building applications on mobile devices An approach to overcome technical limitation occurring as porting applications from desktop computers (moderate screen size) to mobile devices (small screen size) Improvement of quality of the transcoded image from desktop into cell phone Design and implement the authentication of users joining a session during roaming with cell phone devices, and the encryption of messages sent to and from the cell phone devices Support for floor control of synchronous collaborative media applications such as audio / video Optimistic floor control mechanism Means allowing conflicts and resolving them With time-stamp and with different application

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