P2P Networking: Freenet Adriane Lau November 9, 2004 MIE456F

Agenda What is P2P networking? What is Freenet? Philosophy behind Freenet How does Freenet work? Comparison with other P2P networks Future work

*From What is P2P Networking? Direct communication between clients (nodes) No dedicated servers Nodes function as both clients and servers

*From What is Freenet? Decentralized P2P network Allows anonymity of publishers and consumers Shared file storage Encrypted data

*From Philosophy Behind Freenet Importance of free flow of information, communication & knowledge Democracy assumes a well-informed population Censorship restricts freedom Anonymity protects freedom of speech

*From How Does Freenet Work? Privacy  Messages travel through node chains  Nodes can’t tell difference between original & forwarded messages Globally Unique Identifiers (GUID)  Content-hash keys (CHK)  Signed-subspace keys (SSK)

*From How Does Freenet Work? Routing  Forward query to nodes closest to target Requesting files  Requests forwarded until data holder is found Adding files  Generate GUID key & search for it  If “all clear”, data is stored & documented

*Adapted from How Does Freenet Work? a b c d e f Data request Failed request Data reply

*From How Does Freenet Work? Adding a node  Send an announcement to a node  Announcement forwarded randomly; nodes add information about new node Training routes  Nodes on the way back may cache copies  Nodes specialize in searching certain keys

*From How Does Freenet Work? Searching  Currently no search algorithm exists  Proposed solution: keyword files Managing storage  File insertion & storage not restricted  Files prioritized according to popularity; unpopular files deleted when node disk space runs out

Comparison Napster  Centralized server Gnutella  Inefficient broadcasting OceanStore, Cooperative File System, PAST  Data placement dependent on node location

*From Future Work Next generation routing protocol  Aimed to make nodes even “smarter” in routing requests  Each node stores detailed information about other nodes Response time for particular keys Proportion of successful requests Connection time

*From Future Work Search mechanism  Metadata Prevention of denial-of-service attacks Better ways to locate data

Conclusion Freenet is a P2P architecture aimed to protect freedom of speech Messages are forwarded back and forth; nodes can’t tell where a message originated

Thank you! Questions