These types of intermediaries do not host or transmit infringing content, themselves, but may be regarded in some courts as encouraging, enabling or facilitating infringement by users. These intermediaries may include the author, publishers and marketers of peer-to-peer networking software, and the websites that allow users to download such software. In the case of the BitTorrent protocol, intermediaries may include the torrent tracker and any websites or search engines which facilitate access to torrent files. Torrent files don't contain copyrighted content, but they may make reference to files that do, and they may point to trackers which coordinate the sharing of those files. Some torrent indexing and search sites, such as The Pirate Bay, now encourage the use of magnet links, instead of direct links to torrent files, creating another layer of indirection; using such links, torrent files are obtained from other peers, rather than from a particular website.
What protocol do intermediaries use that exclude a torrent tracker?