Packet loss/retransmissions

  1. Is is possible/likely that packets will be come delayed more than 3 secs (the flash buffer size)? I am guessing if they are late by less than 3secs, it should not matter, because flash will sort the packets in the buffer

If the client cannot handle the stream bitrate then eventually the 3 second buffer will be depleted and you will pauses and re-buffering. It sounds like the problem. 800Kbps is pretty high for Internet delivery. We suggest 400-600Kbps in the US.

  1. Does the flash player request for retransmissions for late/lost packets?

RTMP uses TCP. There is no packet loss (not really). If the connection gets behind the player will rebuffer which is what is causing the freezing.

  1. Do these retransmission requests get handled at the TCP level or the application level (wowza)?

If there is true underlying packet loss the TCP protocol will handle the re-transmission requests.

  1. Are there settings in wowza to set up buffer size to handle retransmissions?

No, it is all handled at the TCP level.

Your problem is most likely not packet loss but rather the client connection is lower than the bitrate of the video. You can use the BWChecker to run some tests with folks that are having problems to see how their bitrate measures. I would shoot for a bitrate that is 80% of what the BWChecker measure just to leave some headroom for network congestion.

http://community.wowza.com/t/-/31

Charlie