an overview of peer-to-peer sami rollins srollins

An Overview of Peer-to-Peer

Sami Rollinshttp://www.cs.ucsb.edu/~srollins

Outline

• What is P2P?

• Scope of P2P Applications

• File Sharing Applications

• System Design Challenges

• Approaches to P2P System Design

• Concluding Discussion

What is Peer-to-Peer (P2P)?

What is a peer?

• “…an entity with capabilities similar to other entities in the system.”

The Web Model

• Contact a server and download a web page.

• Server has all the resources and capabilities.

The P2P Model

• A peer’s resources are similar to the resources of the other participants

• P2P – peers communicating directly with other peers and sharing resources

P2P Application Taxonomy

P2P Systems

Distributed ComputingSETI@home

File SharingGnutella

CollaborationJabber

PlatformsJXTA

Distributed Computing

Collaboration

sendMessage receiveMessage sendMessage receiveMessage

Collaboration

sendMessage receiveMessage sendMessage receiveMessage

Platforms

Find Peers … Send Messages

Gnutella Instant Messaging

P2P File Sharing

• Content exchange– Gnutella

• File systems– Oceanstore

• Filtering/mining– Opencola

Challenges

• Peer discovery and group management

• Data location and placement

• Reliable and efficient file delivery

• Security/privacy/anonymity/trust

Design Concerns

• Per-node state

• Bandwidth usage

• Search time

• Fault tolerance/resiliency

Approaches

• Centralized

• Flooding

• Document Routing

CentralizedBob Alice

JaneJudy

Centralized

• Benefits:– Efficient search– Limited bandwidth usage– No per-node state

• Drawbacks:– Central point of failure– Limited scale

Flooding

Bob

Alice

Jane

Judy

Carl

Flooding

• Benefits:– No central point of failure– Limited per-node state

• Drawbacks:– Slow searches– Bandwidth intensive

Document Routing

001 012

212

305

332

212 ?

212 ?

Document Routing

• Benefits:– More efficient searching– Limited per-node state

• Drawbacks:– Limited fault-tolerance vs redundancy

Points of Discussion

• Do P2P applications/systems have common research questions?

• What are the “killer apps” for P2P systems?

• What are the benefits of choosing P2P?

An Overview of Peer-to-Peer

Sami Rollinshttp://www.cs.ucsb.edu/~srollins

Mills College – 2/25/03

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Remaining Problems?

Remaining Problems?

• Hard to handle highly dynamic environments

• Methods don’t consider peer characteristics

• Usable services

P2P Goals/Benefits

• Cost sharing

• Resource aggregation

• Improved scalability/reliability

• Increased autonomy

• Anonymity/privacy

• Dynamism

• Ad-hoc communication