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Many defitions of P2P have been proposed in P2P community. The Intel P2P Working Group \cite{p2pworkinggroup} |
Many defitions of P2P have been proposed in P2P community. The Intel P2P Working Group \cite{p2pworkinggroup} |
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defines P2P as "the sharing of computer resources and services by direct exchange between systems". Ross Lee |
defines P2P as "the sharing of computer resources and services by direct exchange between systems". Ross Lee |
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Graham \cite{graham02lecture} defines P2P through three requirements: 1) System has an operational computer |
Graham \cite{graham02lecture} defines P2P through three requirements: 1) System has an operational computer |
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of server quality; 2) System has an addressing system independent of DNS \cite{rfc1101}; 3) System is able |
of server quality; 2) System has an addressing system independent of DNS; 3) System is able |
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to cope with variable connectivity. O'Reilly's Clay Shirky proposes that "P2P is a class of applications |
to cope with variable connectivity. O'Reilly's Clay Shirky proposes that "P2P is a class of applications |
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that takes advantage of resources - storage, cycles, content, human presence - available at the edges |
that takes advantage of resources - storage, cycles, content, human presence - available at the edges |
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of the Internet. Because accessing the decentralized resources means operating in a environment of unstable |
of the Internet. Because accessing the decentralized resources means operating in a environment of unstable |
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[Figure 1. Insert picture] |
[Figure 1. Insert picture] |
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However, more detailed comparison of P2P systems and client-server approach is significantly more complex |
However, more detailed comparison of P2P systems and client-server approach is significantly more complex |
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along many dimensions: "There is no clear border between a client-server and a P2P model. Both models can be |
because: "There is no clear border between a client-server and a P2P model. Both models can be |
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built on a spectrum of level of characteristics, functionality, organizations, components, protocols etc. Furthermore, |
built on a spectrum of level of characteristics, functionality, organizations, components, protocols etc. Furthermore, |
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one mode can be built on top of the other or parts of the components can be realized in one or the other model. Finally, |
one mode can be built on top of the other or parts of the components can be realized in one or the other model. Finally, |
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both models can execute on different types of platforms and both can server as an underlying base for traditional |
both models can execute on different types of platforms and both can server as an underlying base for traditional |
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\subsection{A brief history} |
\subsection{A brief history} |
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The Internet has been originally established in the late 1960s \cite{oram01harnessingpower}. |
The Internet has been originally established in the late 1960s. The objective of the ARPANET-project was to |
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The aim of the ARPANET-project was to share computers' resources around the |
share computers' resources around the United States. The most challenging purpose of ARPANET was to |
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United States. The most challenging purpose of ARPANET was to integrate different kinds of |
integrate different kinds of existing network technologies with one common network architecture. The |
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existing network technologies with one common network architecture. The ARPANET connected |
ARPANET connected the first few hosts together not in client/server relationship, but rather as |
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the first few hosts together not in client/server relationship, but rather as |
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equal networking peers. This could be seen as starting point both of P2P systems and |
equal networking peers. This could be seen as starting point both of P2P systems and |
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Internet [REFERENCE NEEDED!!!]. |
Internet \cite{oram01harnessingpower}. |
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While most early distributed applications can be considered P2P, e-mail systems and Usenet |
While most early distributed applications can be considered P2P, file transfer protocol (FTP), Usenet and Telnet |
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News were probably the most extensively used. In both cases, local server created connections to |
systems were probably the most extensively used. A Telnet client logged into a server, and |
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other peer servers to deliver messages into the user's mail box or into a spool box |
an FTP client downloaded and sent data to a file server. In the case of Usenet, peer servers connected |
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containing messages from the newsgroups. The File Transfer Protocol (FTP) can be considered as a |
to other peers to deliver messages into the user's mail box or into a spool box containing messages from |
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predecessor to today's file-sharing P2P systems. Eventually, the Archie indexing system, was developed to |
the newsgroups. Altough single application could be seen as was client/server relationship, the usage model as a |
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whole were symmetric. Every computer on the ARPANET could create connections to any other computer and use |
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each other's resources. The symmetry is what made the ARPANET so novel. As a implication, early ARPANET |
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made possible to create more complex systems as DNS \cite{rfc1101}. |
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In subsequent years, the Internet has become more restricted to client/server based applications. In |
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recent years, however, P2P systems have emerged a significant social and technical phenomenon. It could |
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be possible the Internet could revert to its initial symmetrical form. At the end, FTP can be considered as |
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a predecessor to today's file-sharing P2P systems. The Archie, global indexing system, was developed to |
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provide a central search infrastructure over existing FTP servers. Napster \cite{napsterurl} is a good |
provide a central search infrastructure over existing FTP servers. Napster \cite{napsterurl} is a good |
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example of this kind of approach in modern P2P file-sharing systems. |
example of this kind of approach in modern P2P file-sharing systems. |
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\subsection{Characteristics of P2P} |
\subsection{Characteristics of P2P} |
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Decentralization |
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Scalability and adapion |
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Anonymity and Autonomy |
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Self-organization |
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Cost Of ownership |
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ad-hoc connectivity |
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accountability |
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reputation |
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\subsection{Adaptations of P2P} |
\subsection{Adaptations of P2P} |
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\subsection{Models of P2P} |
\subsection{Models of P2P} |