M3U playlists…why redundant files?

Question

I'm taking a look at some random Icecast playlists (available here: http://dir.xiph.org/index.php) and I'm wondering why many seem to contain a list of the same mp3 file.

e.g.:

GET http://dir.xiph.org/listen/193289/listen.m3u

http://87.230.101.49:80/top100station.mp3
http://87.230.103.107:80/top100station.mp3
http://87.230.101.16:80/top100station.mp3
http://87.230.101.78:80/top100station.mp3
http://87.230.101.11:80/top100station.mp3
http://87.230.103.85:80/top100station.mp3
http://80.237.158.87:80/top100station.mp3
http://87.230.101.30:80/top100station.mp3
http://80.237.158.88:80/top100station.mp3
http://87.230.103.9:80/top100station.mp3
http://87.230.103.58:80/top100station.mp3
http://87.230.101.12:80/top100station.mp3
http://87.230.101.24:80/top100station.mp3
http://87.230.103.60:80/top100station.mp3
http://87.230.103.8:80/top100station.mp3
http://87.230.101.25:80/top100station.mp3
http://87.230.101.56:80/top100station.mp3
http://87.230.101.50:80/top100station.mp3

For what it's worth, Icecast streams are intended for playing those Shoutcast-type live streams (think live radio over internet) so it makes sense that there wouldn't be a list of different tracks..but what are those repeats? Different bitrates or just mirrors?

I'm asking all of this because I'm looking to stream one of those mp3s inside my mobile app so I'm wondering if there any need to somehow figure out which url to use...

Answer 1

Internet radio streams are typically mirrored across many servers. This balances the bandwidth load, and reduces points of failure.

In addition, it is common for servers to fill up as they get popular. Most players will go to the next track in the playlist when a track fails, so this allows autofailover when a client cannot connect to a specific server, or if it gets disconnected.