Incentives for sharing in Gnutella

Peers in Gnutella have no incentive to upload

BitTorrent's tit for tat algorithm creates an incentive to upload, but there's a separate BitTorrent swarm for each file

Solution: allow Gnutella peers to exchange something they have for something they want

Could be pieces of the same file, as in BitTorrent
Could be different files
If X has something Y is interested in, there's a better than average chance that Y has something X is interested in

Peers use tit for tat or some other algorithm to allocate bandwidth

Peers with nothing to trade get lower priority
Incentive to upload: you get faster downloads
Incentive to answer queries: you're more likely to find answers to your own queries
Incentive to hoard files: you're more likely to have something suitable to upload

Implementation: "trade queries"

A TradeQuery is piggybacked on a QueryHit using GGEP
The TradeQuery describes what the responder wants in exchange for the files offered in the QueryHit
- Created automatically from the responder's active searches and downloads
The requester can reply to the TradeQuery using a TradeQueryHit
The TradeQueryHit is piggybacked on a Push (using GGEP again)
The responder treats the TradeQueryHit like a hit for one of its own queries (the Push is just used for routing)
The protocol is incrementally deployable - intermediate nodes don't have to understand TradeQueries or TradeQueryHits

m.rogers@cs.ucl.ac.uk
Last modified 2005/12/13