Differences between rtmp and HTTP Based on FLV videos

With the FMS/red5 configuration, use flvplayerback to test the rtmp protocol. To further use netstream for development, we found that netstream. Play only supports HTTP and file protocols (refer to the Flash help ).
Check the Internet for YouTube, 6rooms, and 56, and find that the playing protocols they use are also HTTP. As the Streaming Media Server, the FMS/red5 has been specially optimized. But why are these websites not using the rtmp protocol.

What are the advantages of rtmp over HTTP? Or: Why do we need to use FMS/red5?

The two protocols HTTP and rtmp are slightly different,
HTTP: first download FLV to the local cache through IIS, and then play the FLV through the local connection of netconnection. This method is to play the local video, it is not a video playing server. Therefore, this FLV can be found in the local cache. The advantage is that after the server downloads the FLV, the server will not be consumed, saving the server consumption. The disadvantage is that FLV will be cached on the client, which is not good for the confidentiality of FLV.
Rtmp: connect to the FMS/red5 server through netconnection and play the FLV file of the server in real time. In this way, you can select any video playback point (seek ()), it is not like caching a complete FLV file locally in http mode to select any playback point. The advantage is that the FLV file cannot be found in the local cache. The advantage is that FLV is not cached on the client, and FLV has good confidentiality. Its disadvantage is that it consumes server resources and the connection is always real-time.
In a word, one is local playback, and the other is server real-time playback, depending on your needs.

HTTP currently has a lot of applications, because this does not require support from red5 or the hadoop Management System server. Common web servers can be implemented (virtual hosts)
The other one must have servers, but the confidentiality is stronger.

Why? File = xxx :)