A short overview of p2p technologies Marcelo Dias de Amorim Laboratoire LIP6 Université Pierre et Marie Curie Caen – Le 11 Juin 2003

IPv6 – Caen, 11 juin Plan  Introduction  Models  Example of applications  Some systems  References

IPv6 – Caen, 11 juin Definitions P2P is a class of applications that take advantage of resources – storage, cycles, content, human presence – available at the edges of the Internet. Clay Shirky ( ) P2P refers to a class of systems and applications that employ distributed resources to perform a critical function in a decentralized manner. Milojicic et al. ( HP )

IPv6 – Caen, 11 juin Some controversy  Is p2p a new approach? Problems is peer-to-peer systems are neither new nor unique; they make us look for solutions to old problems that we all worked around or tried to ignore before. Andy Oram (O'Reilly & associates) speech at Free and Open Source Software Developers's Meeting Brussels, BE, Feb. 2002

IPv6 – Caen, 11 juin Curiosity (traffic) Others Unidentified P2P 18% 51% 31% One year ago… 48% 41% 11% … and today! source netflow.internet2.edu

IPv6 – Caen, 11 juin 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

IPv6 – Caen, 11 juin Examples of p2p usage  File-sharing applications  Distributed databases  Distributed computing (grid?)  Collaboration  Distributed games  Instant messaging  Ad hoc networks  Application-level multicast  Etc.

IPv6 – Caen, 11 juin IP Overlay networks Overlay

IPv6 – Caen, 11 juin Overlay networks IP Overlay

IPv6 – Caen, 11 juin 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 (?)

IPv6 – Caen, 11 juin Centralized model (Napster) INTERNET location server register Document x? OK: Peer Z IP = a.b.c.d  Document x! x 

IPv6 – Caen, 11 juin 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)

IPv6 – Caen, 11 juin Gnutella

IPv6 – Caen, 11 juin 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.

IPv6 – Caen, 11 juin 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(n 1/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

IPv6 – Caen, 11 juin Example

IPv6 – Caen, 11 juin Example 1

IPv6 – Caen, 11 juin Example 12

IPv6 – Caen, 11 juin Example

IPv6 – Caen, 11 juin Example

IPv6 – Caen, 11 juin Example

IPv6 – Caen, 11 juin Example

IPv6 – Caen, 11 juin Example

IPv6 – Caen, 11 juin Association ID  node Ex: Node 3 holds this document

IPv6 – Caen, 11 juin Association ID  node

IPv6 – Caen, 11 juin Application-layer multicast  Native multicast  not yet completely deployed  ALM  easier/faster to implement Scalability  states at end-systems High-level support

IPv6 – Caen, 11 juin Application-layer multicast source

IPv6 – Caen, 11 juin Taxonomy P2P Applications Compute Intensive Compo- nentized Content exchange File system Filtering, mining Instant message Shared apps Games Parallel Content and file mngt Collaboration

IPv6 – Caen, 11 juin Many works and projects  Gnutella and

IPv6 – Caen, 11 juin 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

IPv6 – Caen, 11 juin 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)

IPv6 – Caen, 11 juin JXTA (Sun)  Protocols  Peer discovery protocol  Peer resolver protocol  Peer information protocol  Rendezvous protocol  Pipe binding protocol  Endpoint routing protocol

IPv6 – Caen, 11 juin JXTA (Sun) Peer (Desktop, cell phone, PDA, etc.) Security Peer GroupsPeer PipesPeer Monitoring JXTA Community Services Sun JXTA Services JXTA Shell Peer Commands JXTA Community Applications CORECORE JXTAJXTA

IPv6 – Caen, 11 juin JXTA applications

IPv6 – Caen, 11 juin 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.

IPv6 – Caen, 11 juin Working groups et al.  A generic site on p2p from O'Reilly  P2P working group  Internet2 p2p working group p2p.internet2.edu  Peer-to-peer development (p2p-hackers) zgp.org/mailman/listinfo/p2p-hackers  Interesting meeting

IPv6 – Caen, 11 juin References  Distributed Computing Distributed ( ( (gah.stanford.edu) ( Global Grid Forum ( Globus Project (  File sharing Napster ( Gnutella (gnutella.wego.com) Kazaa (

IPv6 – Caen, 11 juin References  Distributed hash tables CAN ( ratnasamy.pdf) Pastry (research.microsoft.com/~antr/Pastry) Chord ( Tapestry ( Freenet (freenet.sourceforge.net) Kademlia (kademlia.scs.cs.nyu.edu)  Ad hoc networking AODV ( aodv-13.txt) OLSR ( 10.txt) Tribe (rp.lip6.fr/site_rp/_publications/350-79Viana.ps.gz)

IPv6 – Caen, 11 juin References  Platforms JXTA ( (  Collaboration Groove ( Endeavors (  IPv6 as a p2p overlay  Working Groups p2p.internet2.edu