in peer-to-peer file sharing, the strength of a swarm depends on user behaviour, as peers ideally upload more than they download. this is done by seeding, and there are different motivations to do this. there are two popular motivations to seed, of which one is the reputation-based incentive mechanism and the other is the tit for tat mechanism. as the name reveals, the former is based on the reputation of a peer, meaning that those peers who have a good reputation will get a better treatment from the uploader. the tit for tat mechanism prevents peers from downloading content if they do not upload to the peers they download from. the latter forces a peer to upload.