In this paper we present a complete measurement study that
compares YouTube traffic generated bymobile devices (smartphones,
tablets) with traffic generated by commons PCs (desktops,
notebooks, netbooks). We investigate the user behavior
and correlate it with the system performance. Our measurements
are performed using unique data sets which are
collected from vantage points in nation wide ISPs and University
campuses of two countries in Europe, and one in the
Our results show that the user access patterns are similar
across a wide range of user locations, access technologies
and user devices. Users stick with default player configurations,
e.g., not changing video resolution or rarely enabling
full screen playback. Furthermore it is very common that
users abort video playback, with 60% of videos watched for
less than 20% of their duration.
We show that the YouTube system is highly optimized
for PC access and leverages aggressive buffering policies to
guarantee excellent video playback. This however causes
25%-39% of transferred data to be unnecessary, since users
abort the playback very early. The unnecessary data transfer
is even higher when mobile devices are considered. The
limited storage offered by those devices makes the video
download more complicated and overall less efficient, so that
clients typically download more data than the actual video
length. This result is particularly critical especially for wireless
networks and calls for better system optimization.

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