On P2P Collaboration Infrastructures Manfred Hauswirth, Ivana Podnar, Stefan Decker Infrastructure...

On P2P Collaboration Infrastructures

Manfred Hauswirth, Ivana Podnar, Stefan DeckerInfrastructure for Collaborative Enterprise, 2005. 14th IEEE International Workshops on 13-15 June 2005Speaker : Ching-Chen ChangDate:2007/12/13  

Overview

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

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.

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.

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.

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.

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

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.

Architecture(1/2)

Device-dependent Presentation

Higher-level services(e.g. instant messaging, white board, alerts)

Distributed Storage

TCP/UDP

Distributed Trust Mng.

Membership Mng.

PresenceService

Publish/Subscribe

Authenticated and

Secure A

ccess Mn

g.

P2P

Architecture for P2P collaboration systems.

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.

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.

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.

Distributed Search and Storage(1/4) It is the question whether complete

consistency is required or some relaxed model would be tolerable.

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.

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.

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.

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.

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.

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