About Flash P2P live streaming from non-webcam sources

Question

Hello, I am a university student. Our lab is attempting to work on a p2p live streaming using flash p2p features. The media source is not from a webcam but a file from a certain server, which is not directly supported by any of the 4 methods flash player offers(posting, direct routing , object replication,and multicast.) As some of the forum threads mentioned, our method is to use NetStream.publish() a stream and use send("callbackname", data)  to all subscribers that have joined in a NetGroup. So we can use p2p transmission. Now here are our questions:
1. We know from MAX 2009 that flash p2p camera video multicasting implements pull-push mechanism inside which makes full use of p2p features like buffer map exchange. If we use NetStream.send() API to send non-webcam source data, will it also make use of this pull-push mechanism to spread data among all peers(subscribers) with proper data exchange?
or more detailedly,
I saw the P2P Gaming Libs at flashrealtime.com. It uses DIRECT_CONNECTIONS when creating publish-used NetStream in order to send data with lowest latency. My question is if I do not use DIRECT_CONNECTIONS, than when the NetGroup grow large (1000), will those peers that are not direct neighbors to the publisher in the same group relay data to each other using pull-push via buffer map?
2. I have written a sample app and use send() to deliver data only (NetStream.bufferTime = 0) without camera video and audio. When the publisher sends the data  in a "for()" stantence for 20 times, the subscribers can only receive about 8 of them. But when I set a timer and periodically send them(e.g., 500ms), the subscribers can receive them correctly. My questions are: Is the packet loss caused by UDP unreliability? Can this be solved by setting the NetStream.dataReliable = ture? Can this totally be solved by setting a timer? How to set the delaytime property in timer? Are all data sent are orderedly received?
I'm very appreciated if you can answer my questions? thanks.

Answer 1

1. NetStream.send() data is delivered in the order it was sent, whether in client-server, DIRECT_CONNECTIONS, or multicast mode.
2. the lowest latency will be achieved with DIRECT_CONNECTIONS.  however, that isn't scalable to large numbers of recipients.  the P2P multicast system trades low latency for scalability.
3. there are no plans to support a natural NetStream streaming source that's not a camera/microphone.  Flash Media Server can perform that function.
4. you should never need to implement "bitmap exchange"; the object replication system handles all the communication needed to accomplish its function. typically you will divide a file into segments, giving each one an index number. object replication uses ranges internally, so the index numbers should be contiguous.  nodes that have indices use NetGroup.addHaveObjects().  nodes that want indices they don't have use NetGroup.addWantObjects().  nodes that have objects will send them to nodes that want the objects.  when a node receives an object, it's automatically removed from its "want" set; once the node decides the object is acceptable, it adds it to its "have" set, at which point it can answer requests from other nodes who still "want" it.  eventually every node will have all the pieces and not want any.  for an example, please see Tom Krcha's articles on using object replication:
   http://www.flashrealtime.com/file-share-object-replication-flash-p2p/
   http://www.flashrealtime.com/video-on-demand-over-p2p-in-flash-player-101-with-object-repl ication/
5. please see Tom Krcha's articles.  for VOD you will probably want to use the "LOWEST_FIRST" replication strategy, as that may allow you to start playing earlier.  for general file replication you'll get better sharing if you use RAREST_FIRST.