Figure 2: The uptime ranking of three types of BitTorrent/Suprnova
global components.
Figure 2 shows the results of our availability measurements
of 234 Suprnova mirrors, 95 .torrent file
servers, and 1,941 BitTorrent trackers (Suprnova.org itself
is not shown). In the figure we plot the average uptime
in days for these global components ranked according
to decreasing uptime. Only half of the Suprnova mirrors
had an average uptime of over 2.1 days, which is a
good indication of their (un)availability. In addition, only
39 mirrors had a continuous uptime period longer than
two weeks. We can conclude that reliable webhosting
of Suprnova pages is a problem. As shown in the figure,
the .torrent file servers are even less reliable. A
few trackers show a high degree of availability, with one
tracker even showing a continuous uptime period of over
100 days. Half of the trackers had an average uptime of
1.5 day or more, and the 100 top ranking trackers had an
average uptime of more than 15.7 days.
In Figure 1 we have shown that unavailability has a
significant influence on popularity. Combined with the
high frequency of such failures as apparent from Figure
2, we conclude that there is an obvious need to decentralize
the global components. However, all the features
that make BitTorrent/Suprnova exceptional (easy singleclick-download
web interface, low level of pollution, and
high download performance) are heavily dependent on
these global components.
The availability of individual peers over a long time
period has never been studied, despite its importance. We
measured peer availability for over three months, which
is significantly longer than reported in [2], [4], and [14].
On December 10, 2003 the popular PC game “Beyond
Good and Evil” from Ubisoft was injected into BitTorrent/Suprnova
and on March 11, 2004 it died. We followed
this content and obtained 90,155 peer IP numbers
using our Getpeer script. Of these IP numbers, only
53,883 were not behind firewalls and could be traced by
our Peerping script. We measured the uptime of all non-
firewalled peers with a one minute resolution.
Figure 3 shows the results of our uptime measurements.
Here we plot the peer uptime in hours after they