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revision 1.186 by hemppah, Tue Mar 25 13:37:05 2003 UTC revision 1.187 by hemppah, Tue Mar 25 13:48:46 2003 UTC
# Line 179  In the loosely structured approach the c Line 179  In the loosely structured approach the c
179  loosely. The placement of services and topology of the overlay is random. The data lookup model in loosely structured systems is  loosely. The placement of services and topology of the overlay is random. The data lookup model in loosely structured systems is
180  not very efficient, because of unstructured properties of the overlay.  not very efficient, because of unstructured properties of the overlay.
181    
182  \subsection{Sketch of a formal definition}  \subsection{Definition}
183    
184  In this subsection we formalize loosely structured overlay's main components. This  In this subsection we formalize loosely structured overlay's main components. This
185  model is based on original Gnutella overlay network with power-law improvements.  model is based on original Gnutella overlay network with power-law improvements.
# Line 296  structured overlays have been proposed. Line 296  structured overlays have been proposed.
296  approach the overlay is constructed determistically, which all participating peers have to follow. The topology of the  approach the overlay is constructed determistically, which all participating peers have to follow. The topology of the
297  overlay and the placement of services is controlled tightly therefore enabling more scalable and efficient data lookup model.  overlay and the placement of services is controlled tightly therefore enabling more scalable and efficient data lookup model.
298    
299  \subsection{Sketch of a formal definition}  \subsection{Definition}
300    
301  In this subsection, we formalize the main features of tightly structured overlay, i.e.,  In this subsection, we formalize the main features of tightly structured overlay, i.e.,
302  identifiers, identifier space and the mapping function.  identifiers, identifier space and the mapping function.
# Line 350  table represent peer's neighbors in the Line 350  table represent peer's neighbors in the
350  \end{figure}  \end{figure}
351    
352  Balakrishnan et al. \cite{balakrishanarticle03lookupp2p} have listed four requirements  Balakrishnan et al. \cite{balakrishanarticle03lookupp2p} have listed four requirements
353  for tightly structured overlays which have to be addressed in order  for tightly structured overlays\footnote{Authors use the term 'DHT' in their text, but in this context
354    it doesn't matter as they list \emph{general} properties of tightly structured overlays.} which have to be addressed in order
355  to perform efficient data lookups in tightly structured overlays.  to perform efficient data lookups in tightly structured overlays.
356  First, mapping of keys to peers must be done in a load-balanced  First, mapping of keys to peers must be done in a load-balanced
357  way. Second, the overlay must be able to forward a data lookup for a  way. Second, the overlay must be able to forward a data lookup for a
# Line 875  Castro et al. \cite{castro02secureroutin Line 876  Castro et al. \cite{castro02secureroutin
876  against the Sybil attack. According to authors, in this technique the IP address of a peer can be verified by the other peer.  against the Sybil attack. According to authors, in this technique the IP address of a peer can be verified by the other peer.
877  They call this method as a one form of \emph{self-certifying data}.  They call this method as a one form of \emph{self-certifying data}.
878    
   
879  In the Fail-stop attack model, cited in \cite{naor03simpledht}, a faulty peer is deleted from the Peer-to-Peer system. Thus,  In the Fail-stop attack model, cited in \cite{naor03simpledht}, a faulty peer is deleted from the Peer-to-Peer system. Thus,
880  a specific data item can be lost from the system temporaraly (or permanently). The reason for the faultiness of a peer can be a  a specific data item can be lost from the system temporaraly (or permanently). The reason for the faultiness of a peer can be a
881  software failure or a hostile attack. The Byzantine attack model \cite{357176} is closely related to Fail-stop model. The Byzantine model can  software failure or a hostile attack. The Byzantine attack model \cite{357176} is closely related to Fail-stop model. The Byzantine model can

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