The Local Peer Discovery protocol is an extension to the BitTorrent file-distribution system. It is designed to support the discovery of local BitTorrent peers, aiming to minimize the traffic through the Internet service provider's (ISP) channel and maximize use of higher-bandwidth local area network (LAN).
Local Peer Discovery is implemented with HTTP-like messages on User Datagram Protocol (UDP) multicast group 18.104.22.168:6771 which is an administratively scoped multicast address. While it is implemented in several clients (µTorrent, BitTorrent/Mainline, MonoTorrent, libtorrent and its derivatives, Transmission 2.0 ) and implementation is very simple, no formal specification had been created as of December, 2009 (although it was supposed to be described in nonexistent BEP 14 by Harrison, Hazel). Alternative multicast protocol extension is published as BEP 26.