Peer-to-Peer Systems: An Overview Hongyu Li

Outline  Introduction  Characteristics of P2P  Algorithms  P2P Applications  Conclusion

Introduction  In client-server model, most resources are concentrated on a small number of nodes.  Most PCs do not use 100 percent of its resources – there is a lot of excess capacity  Better way – distributing processing load and network bandwidth among all nodes or peers.

Introduction  What is P2P “A type of network in which each workstation has equivalent capabilities and responsibilities. This differs from client/server architectures, in which some computers are dedicated to serving the others.”

Introduction Client-Server ModelGeneral P2P Model

Characteristics  Decentralization: emphasis on the user‘s ownership and control of resources  Improved Scalability: An immediate benefit of decentralization  Better Performance: improved by aggregating distributed storage capacity

Characteristics  Increased autonomy: P2P requires the local node do work on behalf of its user  Enhanced privacy: users can avoid having to provide any information about themselves to anyone else  Dynamism: nodes will be entering and leaving the system continuously

Algorithms  Centralized model : all object index items are kept in a centralized server – “hybrid P2P”

Algorithms  Decentralized but unstructured model: “pure P2P” model no advertisement of shared resources occurs the object query is distributed and the logical P2P topology is often random and unstructured

Algorithms

 Decentralized and structured model : the most recent approach object query is also distributed, but the logical P2P topology is the structured topology such as Mesh, Ring, and Butterfly structured topologies are usually constructed using distributed hashing table (DHT) techniques

Algorithms

P2P Applications  Skype a peer-to-peer voice over IP (VoIP) system two types of nodes in the overlay network, ordinary nodes and super nodes (SN). claims to have implemented a “3G P2P” or “Global Index” technology

P2P Applications  BitTorrent peer-to-peer protocol for distributing files use the upstream bandwidth of every downloader to increase the effectiveness of the distribution. upload pieces of the file to each other when downloading

P2P Applications  JXTA peer-to-peer networking platform released by Sun Microsystems attempts to create a framework by providing the capabilities that most P2P applications require provides core functionality in multiple layers, including higher level services, etc.

Conclusion  Challenges security threats – sufficient guarantees or additional trust has to be established among the peers lack of central control – serious challenges to the imposition of authority; breach the laws of various jurisdictions, particularly censorship and copyright

Conclusion  Future an important solution to certain inherent problems in distributed systems a strong alternative for scalability, anonymity, and fault resilience requirements the future of P2P is very promising

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