[ excerpt from developer's web site with modifications ]

One crucial component of the BitTorrent structure is the tracker.
This is a small program which is hosted by someone who wants to
share a file using BitTorrent. Anyone that wants to download that
file needs to connect to the tracker to receive a list of other
peers already participating in the download of the file. The tracker
is a standalone program. If the tracker goes offline, new peers
will not be able to join the download. This makes the tracker the
weak link of the BitTorrent solution.

What if the tracker were able to share its peer list with other
trackers? This would create a redundant network of trackers, all
aware of all peers participating in the download. Peak load would
be reduced, and if one tracker goes offline new peers would still
be able to contact one of the other trackers and join the download.

WWW: http://www.alhem.net/project/trackerbt/index.html