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revision 1.113 by hemppah, Wed Mar 5 10:25:36 2003 UTC revision 1.114 by hemppah, Wed Mar 5 11:31:31 2003 UTC
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1755    
1756  In this chapter we evaluate Fenfire in Peer-to-Peer environment.  In this chapter we evaluate Fenfire in Peer-to-Peer environment.
1757  We start by giving a problem overview when considering Fenfire in Peer-to-Peer  We start by giving a problem overview when considering Fenfire in Peer-to-Peer
1758  environment. We define Fenfire's objectives and special needs. Finally, we  environment. Then, we define Fenfire's objectives and special needs in Peer-to-Peer
1759  evaluate different peer-to-peer approaches with regard to Fenfire, and propose  environment. Finally, we evaluate different peer-to-peer approaches with regard
1760  initial algorihms for obtaining Fenfire specific data from Peer-to-Peer overlay  to Fenfire, and propose initial algorihms for obtaining Fenfire specific data
1761  network.    from Peer-to-Peer overlay network.  
1762    
1763    
 In the following sections, we don't respond to security issues. We assume  
 that either system has a reliable techique for identifying invidual entities, or  
 there are no hostile entities in the system.  
1764    
1765    
1766  \section{Problem overview}  \section{Problem overview}
1767    
1768  As already mentioned in chapter 4, xanalogical document is a ''virtual  As already mentioned in chapter 4, xanalogical document is a ''virtual
1769  file'', in which parts of the document (i.e. scroll blocks) are fetched from a  file'', in which parts of the document are fetched from a
1770  \emph{global} data repository. Thus, system implementing xanalogical model \emph{must}  \emph{global} data repository. Thus, system implementing xanalogical model \emph{must}
1771  support global data lookups efficiently in order to assemble a ''virtual file''  support global data lookups efficiently in order to assemble a ''virtual file''
1772  from fragments of data.  from fragments of data.
1773    
1774  In the xanalogical storage model, each fragment of data is identified by a globally  In the xanalogical storage model, each fragment of data is identified by a globally
1775  unique identifier. As we discussed already in chapter 4, Fenfire's Storm design  unique identifier. In Fenfire, data fragments are scroll blocks of Storm storage module.
1776    As we discussed already in chapter 4, Fenfire's Storm design
1777  uses SHA-1 \footnote{SHA-1 is considered a collision free hash function. Therefore, it is  uses SHA-1 \footnote{SHA-1 is considered a collision free hash function. Therefore, it is
1778  very unlikely that two different Storm scroll blocks would have same identifier.}  very unlikely that two different Storm scroll blocks would have same identifier.}
1779  \cite{fips-sha-1} hash over the contents of a block for creating globally unique  \cite{fips-sha-1} hash over the contents of a scroll block for creating globally unique
1780  identifiers.  In our scenario, fragments of data is distributed throughout the Peer-to-Peer  identifiers for each scroll block.  In our scenario, fragments of data is distributed
1781  overlay. Moreover, our task is to locate and fetch (i.e. obtain) \emph{all}  throughout the Peer-to-Peer overlay. Our task is to locate and fetch
1782  Storm scroll blocks, associated to a specific ''virtual file'', from Peer-to-Peer  (i.e. obtain) \emph{all} Storm scroll blocks, associated to a specific ''virtual
1783  overlay as efficiently as possible. In addition to \emph{direct} scroll block obtaining using  file'', from Peer-to-Peer overlay as efficiently as possible. In addition to
1784  globally unique identifier of Storm block, we also must support \emph{indirect} obtaining of  \emph{direct} scroll block obtaining using globally unique identifier of Storm block,
1785  Storm scroll block using pointer blocks.  we also must support \emph{indirect} obtaining of Storm scroll block using pointer blocks.
1786    
1787  We have decided to use Peer-to-Peer network as a Fenfire's communication layer. For  Some research regarding to these problem has been made by Lukka et al.
1788  motivations and discussion, see \cite{lukka02freenetguids, fallenstein03storm}.  \cite{lukka02freenetguids}. Authors' work is mainly based on insight of implementing
1789  This paper's focus, however, is to evaluate existing Peer-to-Peer systems and their  xanalogical model in Peer-to-Peer enviroment with globally unique identifiers. Lukka et al.
1790  applicably with regard to Fenfire's requirements. Anyhow, it must be feasible to perform  use Freenet \cite{clarke00freenet} as a example Peer-to-Peer system supporting
1791  efficient lookups to locate parts of the document from the global repository based on  globally unique identifiers. This thesis presented here extends their work by
1792  block's identifier. To be more specific, Fenfire's Storm module has to support \emph{global scale}  evaluating different Peer-to-Peer approaches more extensively to Fenfire's needs.
1793  data lookup to locate and fetch scroll blocks by using \emph{location-independent}  Additionally, related to non-xanalogical hypermedia systems, Thompson and de Roure
1794  identifiers.  \cite{thompson01hypermedia} have studied locating documents and links in Peer-to-Peer
1795    environment. Bouving \cite{bouvin02openhypermedia} has done initial work regarding  
1796    
1797    
1798    In the following sections, we don't respond to security issues. We assume
1799    that either system has a reliable techique for identifying invidual entities, or
1800    there are no hostile entities in the system.
1801    
1802    
1803    
 \cite{thompson01hypermedia}  
1804  \cite{wiil02p2phypertext}  \cite{wiil02p2phypertext}
1805  \cite{bouvin02openhypermedia}  
1806    
1807    
1808  \section{Objectives}  \section{Objectives}

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