+ All Categories
Home > Documents > Distributed Systems Concepts and Design Chapter 10: Peer-to-Peer Systems

Distributed Systems Concepts and Design Chapter 10: Peer-to-Peer Systems

Date post: 19-Jan-2016
Category:
Upload: irina
View: 40 times
Download: 0 times
Share this document with a friend
Description:
Distributed Systems Concepts and Design Chapter 10: Peer-to-Peer Systems. Bruce Hammer, Steve Wallis, Raymond Ho. 10.1:Introduction. Peer-to-Peer Systems Where data and computational resources are contributed by many hosts - PowerPoint PPT Presentation
Popular Tags:
19
Distributed Systems Concepts and Design Chapter 10: Peer-to-Peer Systems Bruce Hammer, Steve Wallis, Raymond Ho
Transcript
Page 1: Distributed Systems Concepts and Design  Chapter 10:  Peer-to-Peer Systems

Distributed Systems Concepts and Design Chapter 10: Peer-to-Peer Systems

Bruce Hammer, Steve Wallis, Raymond Ho

Page 2: Distributed Systems Concepts and Design  Chapter 10:  Peer-to-Peer Systems

Bruce Hammer, Steve Wallis, Raymond Ho 2

10.1: Introduction Peer-to-Peer Systems

Where data and computational resources are contributed by many hosts

Objective to balance network traffic and reduce the load on the primary host

Management requires knowledge of all hosts, their accessibility, (distance in number of hops), availability and performance.

They exploit existing naming, routing, data replication and security techniques in new ways

Page 3: Distributed Systems Concepts and Design  Chapter 10:  Peer-to-Peer Systems

Bruce Hammer, Steve Wallis, Raymond Ho 3

10.1: Introduction Goal of Peer-to-Peer Systems

Sharing data and resources on a very large scale ‘Applications that exploit resources available at

the edges of the Internet – storage, cycles, content, human presence’ (Shirky 2000)

Uses data and computing resources available in the personal computers and workstations

Page 4: Distributed Systems Concepts and Design  Chapter 10:  Peer-to-Peer Systems

Bruce Hammer, Steve Wallis, Raymond Ho 4

10.1: Introduction Characteristics of Peer-to-Peer Systems

Each computer contributes resources All the nodes have the same functional

capabilities and responsibilities No centrally-administered system Offers a limited degree of anonymity Algorithm for placing and accessing the data

Balance workload, ensure availability Without adding undue overhead

Page 5: Distributed Systems Concepts and Design  Chapter 10:  Peer-to-Peer Systems

Bruce Hammer, Steve Wallis, Raymond Ho 5

10.1: Introduction Evolution of Peer-to-Peer Systems

Napster – download music, return address Freenet, Gnutella, Kazaa and BitTorrent

More sophisticated – greater scalability, anonymity and fault tolerance

Pastry, Tapestry, CAN, Chord, Kademlia Peer-to-peer middleware

Page 6: Distributed Systems Concepts and Design  Chapter 10:  Peer-to-Peer Systems

Bruce Hammer, Steve Wallis, Raymond Ho 6

10.1: Introduction Evolution (Continued)

Immutable Files, (music, video) GUIDs (Globally Unique Identifiers) Middleware to provide better routing algorithms,

react to outages Evolve to mutable files Application within one company’s intranet

Page 7: Distributed Systems Concepts and Design  Chapter 10:  Peer-to-Peer Systems

Bruce Hammer, Steve Wallis, Raymond Ho 7

10.2: Napster and its Legacy

Page 8: Distributed Systems Concepts and Design  Chapter 10:  Peer-to-Peer Systems

Bruce Hammer, Steve Wallis, Raymond Ho 8

10.2: Napster and Its Legacy

Page 9: Distributed Systems Concepts and Design  Chapter 10:  Peer-to-Peer Systems

Bruce Hammer, Steve Wallis, Raymond Ho 9

10.3: Peer-to-Peer Middleware

Page 10: Distributed Systems Concepts and Design  Chapter 10:  Peer-to-Peer Systems

Bruce Hammer, Steve Wallis, Raymond Ho 10

10.4: Routing Overlays Routing Overlays

Sub-systems, APIs, within the peer-to-peer middleware Responsible for locating nodes and objects Implements a routing mechanism in the application layer

Separate from any other routing mechanisms such as IP routing

Ensures that any node can access any object by routing each request thru a sequence of nodes Exploits knowledge at each node to locate the destination

Page 11: Distributed Systems Concepts and Design  Chapter 10:  Peer-to-Peer Systems

Bruce Hammer, Steve Wallis, Raymond Ho 11

10.4: Routing Overlays GUIDs

‘pure’ names or opaque identifiers Reveal nothing about the locations of the objects Building blocks for routing overlays

Computed from all or part of the state of the object using a function that deliver a value that is very likely to be unique. Uniqueness is then checked against all other GUIDs

Not human readable

Page 12: Distributed Systems Concepts and Design  Chapter 10:  Peer-to-Peer Systems

Bruce Hammer, Steve Wallis, Raymond Ho 12

10.4: Routing Overlays Tasks of a routing overlay

Client submits a request including the object GUID, routing overlay routes the request to a node at which a replica of the object resides

A node introduces a new object by computing its GUID and announces it to the routing overlay

Clients can remove an object Nodes may join and leave the service

Page 13: Distributed Systems Concepts and Design  Chapter 10:  Peer-to-Peer Systems

Bruce Hammer, Steve Wallis, Raymond Ho 13

10.4: Routing Overlays Types of Routing Overlays

DHT – Distributed Hash Tables DOLR – Distributed Object Location and

Routing DOLR is a layer over the DHT that maps GUIDs

and address of nodes DHT – GUIDs are stored based on the hash value DOLR – GUIDs host address is notified using the

Publish() operation

Page 14: Distributed Systems Concepts and Design  Chapter 10:  Peer-to-Peer Systems

Bruce Hammer, Steve Wallis, Raymond Ho 14

10.5: Overlay Case Studies: Pastry, Tapestry

Page 15: Distributed Systems Concepts and Design  Chapter 10:  Peer-to-Peer Systems

Bruce Hammer, Steve Wallis, Raymond Ho 15

10.6: Application Case Studies: Squirrel, OceanStore, Ivy Squirrel

Page 16: Distributed Systems Concepts and Design  Chapter 10:  Peer-to-Peer Systems

Bruce Hammer, Steve Wallis, Raymond Ho 16

10.7: Summary Napster – immutable data, unsophisticated

routing Current – mutable data, routing overlays,

sophisticated algorithms Internet or company intranet support Distributed Computing (SETI)

Page 17: Distributed Systems Concepts and Design  Chapter 10:  Peer-to-Peer Systems

Bruce Hammer, Steve Wallis, Raymond Ho 17

10.7: Summary Benefits of Peer-to-Peer Systems

Ability to exploit unused resources (storage, processing) in the host computers

Scalability to support large numbers of clients and hosts with load balancing of network links and host computer resources

Self-organizing properties of the middleware platforms reduces costs

Page 18: Distributed Systems Concepts and Design  Chapter 10:  Peer-to-Peer Systems

Bruce Hammer, Steve Wallis, Raymond Ho 18

10.7: Summary Weaknesses of Peer-to-Peer Systems

Costly for the storage of mutable data compared to trusted, centralized service

Can not yet guarantee anonymity to hosts

Page 19: Distributed Systems Concepts and Design  Chapter 10:  Peer-to-Peer Systems

Bruce Hammer, Steve Wallis, Raymond Ho 19

10: Peer-to-Peer Systems Questions????

Comments??


Recommended