Local Peer Discovery

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The Local Peer Discovery protocol, specified as BEP-14, [1] 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 networks (LANs).

Local Peer Discovery is implemented [2] with HTTP-like messages on User Datagram Protocol (UDP) multicast group 239.192.152.143:6771 (IPv4) or ff15::efc0:988f (IPv6) [1] which are administratively scoped multicast addresses. It's similar to Simple Service Discovery Protocol but sends BT-SEARCH instead of M-SEARCH:

BT-SEARCH * HTTP/1.1\r\nHost: <host>\r\nPort: <port>\r\nInfohash: <ihash>\r\ncookie: <cookie (optional)>\r\n\r\n\r\n


Since implementation is simple, Local Peer Discovery is implemented in several clients (μTorrent, [3] BitTorrent/Mainline, [4] MonoTorrent, [5] libtorrent [6] and its derivatives, Transmission, [7] aria2 [8] ). An alternative multicast peer discovery protocol based on ZeroConf is published as BEP 26 Zeroconf Peer Advertising and Discovery, but is not widely adopted since it is considered too complex [9] in comparison.

References

  1. 1 2 "BitTorrent Enhancement Proposal 14: Local Service Discovery". BitTorrent.org. 29 October 2015. Retrieved 17 September 2019.
  2. "Protocol Design Discussion » Local Peer Discovery Documentation". 2009-10-30. Retrieved 2009-12-12.
  3. "Announcements » μTorrent 1.7 Release Candidate 6". 2007-06-28. Archived from the original on 2012-03-08. Retrieved 2009-12-12.
  4. "BitTorrent User Manual". Archived from the original on 2009-12-27. Retrieved 2009-12-12.
  5. "MonoTorrent 0.80" . Retrieved 2010-05-05.
  6. "libtorrent manual: features" . Retrieved 2009-12-12.
  7. "Release Notes: Transmission 2.00". GitHub . 2010-06-15. Retrieved 2020-05-23.
  8. "Aria2 Manual: OPTIONS" . Retrieved 2015-09-14.
  9. "Transmission Bug Tracker: ZeroConf Peer Advertising and Discovery" . Retrieved 2016-10-26.