On P2P Collaboration Infrastructures

1. On P2P Collaboration Infrastructures Manfred Hauswirth, Ivana Podnar, Stefan Decker Infrastructure for Collaborative Enterprise, 2005. 14th IEEE International Workshops on 13-15 June 2005Speaker : Ching-Chen Chang Date:2007/12/13  

2. Overview • The paper is about that how distributed mobile collaboration with P2P approaches could be applied.

3. Related Work(1/2) • Three different collaboration scenarios • Ad-hoc • offer temporary support possibly in a limited geographical area, and enable group members to flexibly interact and communicate with limited collaboration functionalities. • Short-term • limited time spans, and enable virtual organizations and teams to collaborate in order to satisfy a mutual objective • Long-term • set up by collaborating organizations and teams for longer time periods. • Usually a centralized infrastructure is used for this type.

4. Related Work(2/2) • Three technological strategies • A standard centralized solution • It seems mainly adequate for long-term collaborations. • A pure P2P approach • This approach would be suitable for ad-hoc and short-term collaborations, but presently can be considered for supporting ad-hoc scenarios which do not require high-reliability and availability of resources. • A mixed model • Provides support for short-term and long-term collaborations.

5. Motivation • Centralized systems require the setup and maintenance of the server. • It requires the infrastructure to be in place and configured a-priori. • It is costly in terms of hardware, software and time. • The P2P approaches could be applied to remedy these shortcomings.

6. Introduction(1/2) • Key characteristics of distributed mobile collaboration are the requirements for flexible interaction styles among users, and ubiquitous mobile access to resources and collaborators.

7. Introduction(2/2) • Much of an overhead, and a more flexible support for short-term and ad-hoc collaboration is required that takes into account user mobility. • The issue of possibly limited functionality of mobile devices

8. Requirements • Users can find and access both required resources and available services. • Efficient distributed search based on semantic descriptions of the involved data, users, services. • Distributed storage, and secure and authenticated access to resources is needed. • Group communication models. • A team membership management service which should be augmented by a trust model.

9. Architecture(1/2) • Architecture for P2P collaboration systems. Device-dependent Presentation Higher-level services(e.g. instant messaging, white board, alerts) Authenticated and Secure Access Mng. Distributed Storage Distributed Trust Mng. Membership Mng. PresenceService Publish/Subscribe P2P TCP/UDP

10. Architecture(2/2) • The transport layer provides the basic network communication between peers. • The peer-to-peer overlay on top of this layer supports basic of nodes, indexing of data and efficient distributed search to increase resource availability. • The five basic lower-level collaboration services which offer supporting services for building end services for mobile collaborators.

11. Distributed Search and Storage(1/4) • Distributed search and replication mechanism • Discovering replicas and supporting up-to-date. • The consistency guarantees provided by the replication mechanism determine the freshness of the information. • Distributed indexing system offers the replication and load-balancing for the index information. • Resources may not be able to be accessed if the corresponding peer is offline. • Replication is required to ensure available of the data.

12. Distributed Search and Storage(2/4) • Distributed archival storage projects split resources into digestible pieces and distribute them. • Coding strategies are needed, but the data manipulation operations are expensive. • Updates in P2P system mean index updates. • The key question for the distributed storage is which data should be replicated.

13. Distributed Search and Storage(1/4) • It is the question whether complete consistency is required or some relaxed model would be tolerable.

14. Distributed Search and Storage(4/4) • Relaxed consistency • When a peer downloads data, it becomes a replica. • In case of an update, all replicas would be informed. • Queries always include the version of the found data. • Conflicting updates require manual system. • If data is unavailable, the requester can subscribe to the system to be notified when the data becomes available.

15. Publish/Subscribe(1/2) • A P/S system provides an efficient service which pushes the data at the time of its publication to interested subscribers. • The major challenge for P/S in such environments is related to the design of efficient routing strategies that can deal with network changes (“churn”) while preserving high-expressiveness of subscriptions and low latency for delivered data.

16. Publish/Subscribe(2/2) • How to match a published notification to the existing subscriptions in the index and how to build delivery trees based on P2P systems. These and related questions are subject of ongoing research.

17. Presence • Presence service maintains and offers information on users’ presence and contact information. • A user can define a default communication point which is activated in case the current presence information is unavailable. • P/S is the natural interaction style for the presence service. • Presence implementation can largely rely on an existing P/S implementation taking into account an extension related to user privacy.

18. Conclusion • We are convinced that P2P-based collaboration is a paradigm that meets the requirements of users, but there is still a lack of enabling technologies which have to be researched and implemented.

19. Reference • On P2P Collaboration Infrastructures http://www.ieeexplore.ieee.org/iel5/10476/33223/01566187.pdf?tp=&arnumber=1566187&isnumber=33223 • P2P架構發展與議題 web.ydu.edu.tw/~hjw/course/p2p/ref01.ppt