===unstructured Peer-to-Peer architectures===
*randomized Algorithms for constructing the overlay Network
*Each Node maintains a List of neighbors
*Random Graph, partial View, push and pull Mode
===topology Management of overlay Networks===
*two layers:
** Random overlay
***nodes Exchange entries periodically, Random graph
**structured overlay
***gets Data from lower Layer
***additional information
***ranking, ordering by distance, Age, semantic proximity
===superpeers===
*avoid Request flooding
*CDN use brokers
*handle all nodes Communication
*highly available, Backup schemes
==Hybrid architectures==
===Edge-Server Systems==
*Hybrid Architecture
*Clients connect via ISP Edge Servers
===collaborative distributed Systems===
*Bit torrent: p53 F2-14



==architectures versus middleware==
*specific architectural style
**Object-based like CORBA
**Event-Based like TIB/Rendezvous
*drawback middleware-application
*requirements: easy to configure, adapt, customize
*Separation between policies and mechanisms
===interceptors===
;interceptor: Software constructing that Breaks the usual Flow and executes other code



==Fault tolerance==
*a partial failure in a distributed system may affect operation of other components
*Important Goal: automatically Recovery from partial failures
;process resilience: processes can fail without disturbing other Processes
*reliable multicasting for messages transmission
*Atomicity
===Introduction to fault tolerance===
====Basic Concepts====
#Availability
#Reliability