/[gzz]/gzz/Documentation/misc/hemppah-progradu/masterthesis.tex
ViewVC logotype

Diff of /gzz/Documentation/misc/hemppah-progradu/masterthesis.tex

Parent Directory Parent Directory | Revision Log Revision Log | View Patch Patch

revision 1.142 by hemppah, Thu Mar 13 13:47:15 2003 UTC revision 1.143 by hemppah, Thu Mar 13 14:06:35 2003 UTC
# Line 237  data lookup works as follows: peer broad Line 237  data lookup works as follows: peer broad
237  forwards the query to their neighbors. This leads to a situation where number of messages  forwards the query to their neighbors. This leads to a situation where number of messages
238  in the network can grow with $O(n^{2})$, where $n$ is the number of participating peers in  in the network can grow with $O(n^{2})$, where $n$ is the number of participating peers in
239  Gnutella network. To limit the amount of network traffic, Gnutella uses Time-To-Live-limited  Gnutella network. To limit the amount of network traffic, Gnutella uses Time-To-Live-limited
240  (TTL) flooding to distributed queries. Therefore, Gnutella uses a Breadth-First-Search (BFS) algorithm  (TTL) flooding to distribute queries. Therefore, Gnutella uses a Breadth-First-Search (BFS) algorithm
241  with depth limit $T$ (e.g., 7), where $T$ is the system-wide maximum TTL of a message in hops. Thus,  with depth limit $T$ (e.g., 7), where $T$ is the system-wide maximum TTL of a message in hops. Thus,
242  only peers that are TTL hops away from the query originator will forward the query or respond to the query.  only peers that are TTL hops away from the query originator will forward the query or respond to the query.
243  In Gnutella network, search results are fast, because BFS sends queries to  In Gnutella network, search results are fast, because BFS sends queries to
# Line 334  Symphony \cite{gurmeet03symphony}, SWAN Line 334  Symphony \cite{gurmeet03symphony}, SWAN
334  The biggest difference compared to loosely structured approach is that with tightly structured systems,  The biggest difference compared to loosely structured approach is that with tightly structured systems,
335  it is now feasible to perform \emph{global} data lookups in the overlay.  it is now feasible to perform \emph{global} data lookups in the overlay.
336  While there are significant differences among proposed systems, they all have in common  While there are significant differences among proposed systems, they all have in common
337  that \emph{peer identifiers} is assigned to participating peers from  that \emph{peer identifiers} are assigned to participating peers from
338  a large \emph{identifier space} by the overlay. Furthermore, application-specific  a large \emph{identifier space} by the overlay. Furthermore, application-specific
339  data items are also assigned globally unique identifiers, \emph{keys},  data items are also assigned globally unique identifiers, \emph{keys},
340  which are selected from the same identifier space. The form of identifier  which are selected from the same identifier space. The form of identifier
# Line 366  All messages are routed across overlay l Line 366  All messages are routed across overlay l
366  peer identifier is gradually ''closer'' to the key's identifier  peer identifier is gradually ''closer'' to the key's identifier
367  in the identifier space. Distance can be measured by numerical  in the identifier space. Distance can be measured by numerical
368  difference between identifiers (e.g., Chord \cite{stoica01chord}), the number of  difference between identifiers (e.g., Chord \cite{stoica01chord}), the number of
369  same prefix bits between identifiers (e.g., Pastry \cite{rowston01pastry} and Tapestry \cite{zhao01tapestry}),  same prefix bits between identifiers (e.g., Pastry \cite{rowston01pastry} and Tapestry \cite{zhao01tapestry}) or
370  bit-wise exclusive or (XOR) (e.g., Kademlia \cite{maymounkov02kademlia}).  bit-wise exclusive or (XOR) (e.g., Kademlia \cite{maymounkov02kademlia}).
371  Because of XOR-metric, Kademlia's distance function is both unidirectional  Because of XOR-metric, Kademlia's distance function is both unidirectional
372  (for a given point $p_i$ in the identifier space and distance $d$ > 0, there  (for a given point $p_i$ in the identifier space and distance $d$ > 0, there
# Line 387  Skip Graphs \cite{AspnesS2003} and SWAN Line 387  Skip Graphs \cite{AspnesS2003} and SWAN
387  overlay, but in which queries are routed  to \emph{keys}. In these systems  overlay, but in which queries are routed  to \emph{keys}. In these systems
388  peer occupies several positions in the identifier space, one for each  peer occupies several positions in the identifier space, one for each
389  application-specific key. The indirection of placing close keys in the  application-specific key. The indirection of placing close keys in the
390  custody of a storing peer\footnote{Storing peer is the peer in the overlay which stores the  custody of a storing peer\footnote{Storing peer is the peer in the overlay which is responsible for the
391  assigned keys.} keys is removed at the cost of each peer maintaining one  assigned keys.} keys is removed at the cost of each peer maintaining one
392  ''resource peer'' in the overlay network for each resource item pair it publishes.  ''resource peer'' in the overlay network for each resource item pair it publishes.
393    
# Line 588  approach and tightly structured approach Line 588  approach and tightly structured approach
588  \\ \hline  \\ \hline
589    
590  \parbox{90pt}{Construction and maintenance of overlay} &  \parbox{90pt}{Construction and maintenance of overlay} &
591  \parbox{100pt}{uncontrolled and ad hoc}  &  \parbox{100pt}{Uncontrolled and ad hoc}  &
592  \parbox{100pt}{Controlled and structured}  \parbox{100pt}{Controlled and structured}
593  \\ \hline  \\ \hline
594                                        
# Line 2016  technologies with Fenfire, if applicable Line 2016  technologies with Fenfire, if applicable
2016  \chapter{Conclusions and future work}  \chapter{Conclusions and future work}
2017    
2018  In this thesis, we have reviewed existing Peer-to-Peer approaches, algorithms and  In this thesis, we have reviewed existing Peer-to-Peer approaches, algorithms and
2019  their properties. Currently, two main Peer-to-Peer overlay approaches  their properties.  We summarized open problems in Peer-to-Peer networks. Specifically,
 exist: loosely and tightly structured overlays. We have discussed differences,  
 disadvantages and advantages of both approaches.  
   
 After that, we summarized open problems in Peer-to-Peer networks. Specifically,  
2020  we divided open problems into three sub-categories: security related problems,  we divided open problems into three sub-categories: security related problems,
2021  performance related problems and miscellaneous problems. Each of these  performance related problems and miscellaneous problems. Each of these
2022  sub-categories have number of open problems, in which there are no solutions  sub-categories have number of open problems, in which there are no solutions
# Line 2031  Then, we focused our attention to Fenfir Line 2027  Then, we focused our attention to Fenfir
2027  overview of Fenfire and xanalogical model. We also described Storm,  overview of Fenfire and xanalogical model. We also described Storm,
2028  which is an essential part of Fenfire's Peer-to-Peer functionality.  which is an essential part of Fenfire's Peer-to-Peer functionality.
2029    
2030  In last chapter, we evaluated existing Peer-to-Peer approaches with regard  In the last chapter, we evaluated existing Peer-to-Peer approaches with regard
2031  to Fenfire's needs. We proposed, that tightly structured approach is the  to Fenfire's needs. We proposed that tightly structured approach is the
2032  best alternative to Fenfire's needs for the following reasons. First, Storm, xanalogical  best alternative to Fenfire's needs for the following reasons. First, Storm, xanalogical
2033  model and tightly structured systems use global unique identifiers  model and tightly structured systems use global unique identifiers
2034  for identifying data. Second, our Storm design uses \emph{semantic-free references}  for identifying data. Second, our Storm design uses \emph{semantic-free references}
# Line 2042  hash \cite{fips-sha-1}. As the authors o Line 2038  hash \cite{fips-sha-1}. As the authors o
2038  we also agree that tightly structured overlays provide general purpose  we also agree that tightly structured overlays provide general purpose
2039  interface to next-generation reference resolution services. Third, by using  interface to next-generation reference resolution services. Third, by using
2040  DOLR abstraction of tightly structured overlay, we can minimize the lack  DOLR abstraction of tightly structured overlay, we can minimize the lack
2041  of locality in tightly structured overlays. Finally, we believe that issues  of locality in tightly structured approach. Finally, we believe that issues
2042  related to tightly structured overlays are solved in near future, because of  related to tightly structured overlays are solved in near future, because of
2043  wide and intensive co-operation among research groups.  wide and intensive co-operation among research groups.
2044    

Legend:
Removed from v.1.142  
changed lines
  Added in v.1.143

savannah-hackers-public@gnu.org
ViewVC Help
Powered by ViewVC 1.1.26