A short overview of p2p technologies

1
A short overview of p2p technologies

• Marcelo Dias de Amorim
• Laboratoire LIP6
• Université Pierre et Marie Curie
• http//www.lip6.fr/

Caen Le 11 Juin 2003
2
Plan

• Introduction
• Models
• Example of applications
• Some systems
• References

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Definitions
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Some controversy

• Is p2p a new approach?

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Curiosity (traffic)
source netflow.internet2.edu
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Properties

• No central control, no central database
• No hierarchy
• Every node is both a client and a server
• The communication between peers is symmetric
• No global view of the system
• Scalablity
• Availability for any peer
• Peers are autonomous
• System globally unreliable
• Robustness and security issues

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Examples of p2p usage

• File-sharing applications
• Distributed databases
• Distributed computing (grid?)
• Collaboration
• Distributed games
• Instant messaging
• Ad hoc networks
• Application-level multicast
• Etc.

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Overlay networks
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Overlay networks
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Centralized model (Napster)

• File-sharing system
• Almost distributed system
• The location of a document is centralized
• The "transfer" is peer-to-peer
• Problems
• Robustness
• Scalability (?)

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Centralized model (Napster)
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Non-structured system (Gnutella-like)

• Two phases (like Napster)
• Localization exchange
• No server
• Open source
• gnutella.wego.com
• Distributed search
• The query is flooded
• Loop avoidance
• Limited TTL (not all nodes are visited)

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Gnutella
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Structured systems (DHTs)

• Based on distributed hash tables (DHTs)
• No flooding
• Exact matches
• Overhead
• Gnutella-like ? O(n)
• DHT ? O(log n)
• Examples
• CAN, Pastry, Chord, Kademlia, Tapestry, etc.

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Content-Addressable Networks (CAN)

• Provides a large scale distributed hash table
• Keys are mapped into values
• CAN defines a d-dimensional virtual space
• No relationship with the physical space
• Query ? O(n1/d)
• Neighbors ? O(d)
• The virtual space is completely distributed among
  the peers
• Each peer is responsible for one share of the
  space
• The peer that is responsible for region R is also
  responsible for the values inside R
• Documents must be uniquely identified

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Example
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Example
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Example
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Example
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Example
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Example
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Example
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Example
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Association ID ? node
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Association ID ? node
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Application-layer multicast

• Native multicast ? not yet completely deployed
• ALM ? easier/faster to implement
• Scalability ? states at end-systems
• High-level support

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Application-layer multicast
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Taxonomy
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Many works and projects

• Gnutella and Napster _at_sourceforge.net

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JXTA (Sun)

• Open platform for p2p cooperation
• Interoperability
• Any system/peer/application
• Platform independency
• Languages (C, Java, etc)
• Systems platforms (Unix, Windows, etc)
• Networking platforms (802.11, Bluetooth, TCP/IP,
  etc)
• Ubiquity
• Sensors, PDAs, routers, desktops, laptops,
  storage systems

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JXTA (Sun)

• Objectives
• Find peers and resources
• Share files with anyone across the network
• Create a particular group of peers across
  different networks
• Communicate securely with peers across public
  networks
• Projects
• Applications (24 projects)
• Core (13 projects)
• Demos (3 projects)
• Forge (15 projects)
• Other (12 projects)
• Services (24 projects)

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JXTA (Sun) ? Protocols

• Peer discovery protocol
• Peer resolver protocol
• Peer information protocol
• Rendezvous protocol
• Pipe binding protocol
• Endpoint routing protocol

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JXTA (Sun)
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JXTA applications
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Final remarks

• P2P implies a very large spectrum of areas
• High interest in both academicals/industrials
• Much has already been done, but no conclusions
  are definitive
• IPv6 and P2P
• NAT, firewalls, IPv6 as an overlay
• Many open issues
• Trust, security, scalability, QoS, etc.

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Working groups et al.

• A generic site on p2p from O'Reilly
• www.openp2p.com
• P2P working group
• www.peer-to-peerwg.org/
• Internet2 p2p working group
• p2p.internet2.edu
• Peer-to-peer development (p2p-hackers)
• zgp.org/mailman/listinfo/p2p-hackers
• Interesting meeting
• www.codecon.org

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References

• Distributed Computing
• Distributed (www.distributed.net)
• SETI_at_home (www.seti.org)
• Genome_at_home (gah.stanford.edu)
• Folding_at_home (www.stanford.edu/group/pandegroup/fo
  lding)
• Global Grid Forum (www.globalgridforum.org)
• Globus Project (www.globus.org)
• File sharing
• Napster (www.napster.com)
• Gnutella (gnutella.wego.com)
• Kazaa (www.kazaa.com)

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References

• Distributed hash tables
• CAN (www.acm.org/sigs/sigcomm/sigcomm2001/p13-ratn
  asamy.pdf)
• Pastry (research.microsoft.com/antr/Pastry)
• Chord (www.pdos.lcs.mit.edu/chord)
• Tapestry (www.cs.berkeley.edu/ravenben/tapestry)
• Freenet (freenet.sourceforge.net)
• Kademlia (kademlia.scs.cs.nyu.edu)
• Ad hoc networking
• AODV (www.ietf.org/internet-drafts/draft-ietf-mane
  t-aodv-13.txt)
• OLSR (www.ietf.org/internet-drafts/draft-ietf-mane
  t-olsr-10.txt)
• Tribe (rp.lip6.fr/site_rp/_publications/350-79Vian
  a.ps.gz)

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References

• Platforms
• JXTA (www.jxta.org)
• .NET (www.microsoft.com/net)
• Collaboration
• Groove (www.groove.net)
• Endeavors (www.endeavors.com)
• IPv6 as a p2p overlay
• Working Groups
• p2p.internet2.edu
• www.openp2p.com