A streaming server is needed to classic streaming to operate through networks. Wikipedia
Comparison of streaming media systems on Wikipedia.
You need no streaming server to stream with Datarhei/Restreamer! YouTube or Ustream are offering free streaming for quite a lot of spectators. If you can stream over the Datarhei/Restreamer iFrame to your own webspace you need per viewer between 300 kb/s and 1.5 Mbit/s upload speed, depending on the subject and quality of your video streams Example: If you for example have a VDSL line with 10 Mbit/s upload at home, you can deliver between about 10 to 30 simultaneous viewers.