[Gzz-commits] gzz/Documentation/misc/hemppah-progradu existin...

[Hermanni Hyytiälä]

CVSROOT:        /cvsroot/gzz
Module name:    gzz
Changes by:     Hermanni Hyytiälä <address@hidden>      02/10/31 03:15:01

Modified files:
        Documentation/misc/hemppah-progradu: existing_systems_overview 

Log message:
        Added little text about the architectures of existing p2p systems

CVSWeb URLs:
http://savannah.gnu.org/cgi-bin/viewcvs/gzz/gzz/Documentation/misc/hemppah-progradu/existing_systems_overview.diff?tr1=1.1&tr2=1.2&r1=text&r2=text

Patches:
Index: gzz/Documentation/misc/hemppah-progradu/existing_systems_overview
diff -u gzz/Documentation/misc/hemppah-progradu/existing_systems_overview:1.1 
gzz/Documentation/misc/hemppah-progradu/existing_systems_overview:1.2
--- gzz/Documentation/misc/hemppah-progradu/existing_systems_overview:1.1       
Wed Oct 30 06:47:30 2002
+++ gzz/Documentation/misc/hemppah-progradu/existing_systems_overview   Thu Oct 
31 03:15:01 2002
@@ -1,3 +1,12 @@
+[This document is meant to be an overview of existing p2p systems. 
+Document is related to address@hidden's Master Thesis project.
+
+Please notice that document's contents are updated constantly.]
+
+
+
+1. A summary of algorithms used in existing systems
+
 Comparison of efficiency of object location in existing distributed 
 (p2p) systems (n is the number of nodes):
 
@@ -16,7 +25,11 @@
 Search: 
 Number of messages when an object lookup is performed
 
-1. Chord
+The table above has been presented in [1].
+
+2. A brief description of existing systems
+
+2.1. Chord
 
 -Chord constructs a distributed lookup service using a routing table of 
 logarithmic size. 
@@ -29,7 +42,7 @@
 -Consistent hashing (distributed hash table)
 
 
-2. CAN
+2.2. CAN
 
 -CAN places objects into a virtual space. 
 -Each peer logically occupies a zone in a virtual space (n dimensional)
@@ -39,7 +52,7 @@
 destination.
 -Consistent hashing (distributed hash table)
 
-3. Tapestry
+2.3. Tapestry
 
 -Location and routing architecture (Plaxton, Rajaraman and Richa)
 -Distributed data structure
@@ -47,17 +60,67 @@
 locality
 
 
-3. Gnutella
+2.3. Gnutella
 
 -Bounded broadcast mechanism used for searching
+-Power law degree distribution
 
-4. FreeNet
+2.4. FreeNet
 
 -Chaotic routing scheme where objects are published to a few nearest 
 neighbors
 -Queries follow gradients generated by object pointers
+-Power law degree distribution
+
+3. Different architectures for p2p networks [2]:
+
+3.1 Centralized
 
+-These kind of systems have a constantly updated database/directory 
+which is hosted at central locations.
+-Nodes in the p2p networks performs a requests to the central directory 
+server to find other nodes and/or files
+-Do not scale well
+-Have a single point of failure
+-Example: Napster
+
+3.2 Decentralized but Structured
+
+-Systems have no central server, but have a great amount of structure
+-In this case, structure means that  p2p network's topology and 
+distribution of resources are tightly controlled 
+-Freenet is an example of "loosely structured" p2p system: distribution 
+of resources is based on hints
+-CAN, Chord, Pastry, Tapestry are examples of "higly structured" p2p 
+systems: both the p2p network topology and the distribution of resources 
+are tightly controlled
+-Hash-table-like interface
+-Prevalant in the research literature but almost invisible on the 
+current p2p networks
+-Isn't clear how well "highly structured" p2p systems work with in real 
+life
+
+
+3.3 Decentralized and Unstructured
+
+-There is neither a centralized server/directory nor any precise control 
+over the network topology or resource distribution
+-Gnutella is an example of decentralized and unstructured p2p system
+-p2p network is is created by nodes joining the network with some loose 
+rules
+-The resultant topology has a certain properties, but placement of 
+resources is not controlled
+-To find a resource, node sends a request to its neighbours
+-The most typical request method is flooding: request is propagated to 
+all neighbours within a certain radius
+-Search mechanisms are unscalable: a great amount of loads are generated 
+on the network during search requests
 
 
+Bibliography:
 
+[1] Hildrum Kirsten, Kubiatowicz John D., Rao Satish and Zhao Ben Y., 
+Distributed Object Location in a Dynamic Network
 
+[2] Lv, Qin, Cao Pei, Cohen Edith, Li Kai, Shenker Scott, Search and 
+Replication in Unstructured Peer-to-Peer Networks